Q on tubular tires (long)
wein...@hotmail.com
they are trouble-free, but upon occaision a puncture has been
experienced. I mount and repair my own tubulars. Here, I have a couple
of questions and would appreciate insight from those perhaps more
experienced.
If I have a flat on the road, I change the tire to a spare. My spare is
normally a previously repaired tubular tire in good condition.
Normally, I figure the ride is basically over and turn around for home.
However, assuming the spare is inflated properly, how hard can I "push
it"? Obviously, the concern here is rolling a tire that is not properly
glued, yet. I'm not talking about screaming down my favorite decent at
50+ mph. But, if I'm 10 miles into a 30 mile ride, should I just finish
the ride, or cruise home slowly at the most direct route?
Second Q, when gluing the tire to the rim, the base tape is actually
glued to the rim, and a different adhesive attaches the base tape to
the tire casing. With a repaired tubular, the base tape has been
removed at least in part, and then re-glued. Doesn't that then imply
that the strength of the tire gluing job is only going to be as good as
the base tape bond?
For me, re-attaching the base tape has been the principal challenge in
repairing the tubulars. I've tried "Tire Life" and that French contact
cement that comes in the Velox kit. Neither is totally confidence
inspiring, although the "Tire Life" on the casing and base tape seems
to provide a better surface for the French contact cement to bond to. I
know "latex emulsion" has been mentioned several times, but I'm not
enough of a chemist to figure out which carpet glue at Home Depot is
going to have properties adequate for a bicycl tire.
Finally, are all contact cements created equal? What are the key
properties of the contact cement in the Velox kit?
Thanks and regards,
Rob
Dave
"Barge Cement" brand glue, available at hardware stores, works well for
base tapes (Lennard Zinn, the tech guru for Velonews recommends it).
As long as the spare has been pre-glued, and there's a good base layer
of glue on the rim, your spare should be fine for anything short of
crit racing. Personally, when I put on a spare during a ride, I find
that when I get home the spare has bonded to the point that I need a
tire lever to pry it off.
Personally, because I want to be able to finish my ride even if I flat,
I don't like the idea of using a worn-out tire as a spare, since a worn
tire is more likely to puncture and with no spare you're in deep
doo-doo. My spare is a Tufo training tire with sealant in it and lots
of tread left, very unlikely to puncture.
russell...@yahoo.com
> As a user of tubular tires, I enjoy the feel and the ride. Generally,
> they are trouble-free, but upon occaision a puncture has been
> experienced. I mount and repair my own tubulars. Here, I have a couple
> of questions and would appreciate insight from those perhaps more
> experienced.
>
> If I have a flat on the road, I change the tire to a spare. My spare is
> normally a previously repaired tubular tire in good condition.
> Normally, I figure the ride is basically over and turn around for home.
> However, assuming the spare is inflated properly, how hard can I "push
> it"? Obviously, the concern here is rolling a tire that is not properly
> glued, yet. I'm not talking about screaming down my favorite decent at
> 50+ mph. But, if I'm 10 miles into a 30 mile ride, should I just finish
> the ride, or cruise home slowly at the most direct route?
I have always continued the ride when I replaced a tubular on the road.
Whether that happened at the beginning or middle or towards the end of
the ride, it did not shorten the ride at all. I was more concerned
about a second flat for the remainder of the ride since I had no more
spare tubulars to use. Jobst Brandt has mentioned that air pressure is
the main thing keeping your tubular tire on the rim, not the glue. So
make sure you have a Blackburn FP1 frame pump and you can put 150 psi
in your tubular tire and it will be stuck on the rim until you let the
air out.
>
> Second Q, when gluing the tire to the rim, the base tape is actually
> glued to the rim, and a different adhesive attaches the base tape to
> the tire casing. With a repaired tubular, the base tape has been
> removed at least in part, and then re-glued. Doesn't that then imply
> that the strength of the tire gluing job is only going to be as good as
> the base tape bond?
I use Goop brand glues available at hardware stores and Wal-Mart to
glue the base tape back on after fixing a tube in a tubular. It holds
the base tape better than the weak base tape glue Continental uses. I
figure the reglued base tape area is better than the rest of the base
tape. I'm more concerned about the unfixed parts of the base tape
coming off than about my fixed portion.
John Forrest Tomlinson
>As a user of tubular tires, I enjoy the feel
Yeah, the feel is so nice. Indescribly nice in fact.
JT
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jobst....@stanfordalumni.org
> As a user of tubular tires, I enjoy the feel and the ride.
> Generally, they are trouble-free, but upon occasion a puncture has
> been experienced. I mount and repair my own tubulars. Here, I have
> a couple of questions and would appreciate insight from those
> perhaps more experienced.
> If I have a flat on the road, I change the tire to a spare. My
> spare is normally a previously repaired tubular tire in good
> condition. Normally, I figure the ride is basically over and turn
> around for home. However, assuming the spare is inflated properly,
> how hard can I "push it"? Obviously, the concern here is rolling a
> tire that is not properly glued, yet. I'm not talking about
> screaming down my favorite decent at 50+ mph. But, if I'm 10 miles
> into a 30 mile ride, should I just finish the ride, or cruise home
> slowly at the most direct route?
I think you are not convinced of your tubular repairs. Those patched
tires should be as good a new if you do it right. When riding alone
on tubulars, taking two spare tires is a good precaution and they
don't take up much space under the saddle.
> Second Q, when gluing the tire to the rim, the base tape is actually
> glued to the rim, and a different adhesive attaches the base tape to
> the tire casing. With a repaired tubular, the base tape has been
> removed at least in part, and then re-glued. Doesn't that then
> imply that the strength of the tire gluing job is only going to be
> as good as the base tape bond?
Yes, but that should be well re-secured using latex emulsion. What
may not be apparent is that unless the wheel is side slipped with the
wheel perpendicular to the road, there are no side forces that would
roll the tire. This became obvious to me after a fast descent on
which I and a friend had cornered hard and after which he got a flat.
For the tire change, the tire practically fell off without effort.
He recalled that this was an old dry spare tire and that his rim was
almost devoid of glue when he mounted it. Fortunately the tire had
globs of hardened glue that registered in the spoke sockets and
prevented tire creep. A vector diagram of a bicycle leaned at 45
degrees makes apparent what these forces are.
Just the same you might find something useful in the following
articles:
http://www.sheldonbrown.com/brandt/tubular-repair.html
http://www.sheldonbrown.com/brandt/making-tubulars.html
http://www.sheldonbrown.com/brandt/tubular-folding.html
http://www.sheldonbrown.com/brandt/mounting-tubulars.html
http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html
http://www.sheldonbrown.com/brandt/tubular-fables.html
> For me, re-attaching the base tape has been the principal challenge
> in repairing the tubulars. I've tried "Tire Life" and that French
> contact cement that comes in the Velox kit. Neither is totally
> confidence inspiring, although the "Tire Life" on the casing and
> base tape seems to provide a better surface for the French contact
> cement to bond to. I know "latex emulsion" has been mentioned
> several times, but I'm not enough of a chemist to figure out which
> carpet glue at Home Depot is going to have properties adequate for a
> bicycle tire.
Make sure it is pure latex emulsion. It cures to a clear light tan
rubber.
http://www.magicmakers.com/retail/makeup%20nye/latex.html
> Finally, are all contact cements created equal? What are the key
> properties of the contact cement in the Velox kit?
For rim glue, don't use something that is so hard to separate that you
can't change a tire without destroying the tire you are pulling off.
It must be tacky enough to re-mount a spare and soft enough so you can
get the tire off. This has been studied to death more than 50 years
ago when tubulars were the only tires used for racing and sport
bicycles. The tire specific adhesive offered by the tubular
manufacturers are the best for this application. You will have to
discover which one fits your use best.
Jobst Brandt
Tom Nakashima
"John Forrest Tomlinson" <usenet...@jt10000.com> wrote in message
news:fmglk113uoh8he0u9...@4ax.com...
Do you mean indescribably?
-tom
John Forrest Tomlinson
<t...@slac.stanford.edu> wrote:
>
>"John Forrest Tomlinson" <usenet...@jt10000.com> wrote in message
>news:fmglk113uoh8he0u9...@4ax.com...
>> On 10 Oct 2005 11:04:54 -0700, wein...@hotmail.com wrote:
>>
>>>As a user of tubular tires, I enjoy the feel
>>
>> Yeah, the feel is so nice. Indescribly nice in fact.
>
>Do you mean indescribably?
Yes.
Jasper Janssen
>Personally, because I want to be able to finish my ride even if I flat,
>I don't like the idea of using a worn-out tire as a spare, since a worn
>tire is more likely to puncture and with no spare you're in deep
>doo-doo. My spare is a Tufo training tire with sealant in it and lots
>of tread left, very unlikely to puncture.
Yeah? And if you then flat the *other* non tufo tyre?
Jasper
Jasper Janssen
<usenet...@jt10000.com> wrote:
>On Mon, 10 Oct 2005 12:43:10 -0700, "Tom Nakashima"
><t...@slac.stanford.edu> wrote:
>>"John Forrest Tomlinson" <usenet...@jt10000.com> wrote in message
>>news:fmglk113uoh8he0u9...@4ax.com...
>>> On 10 Oct 2005 11:04:54 -0700, wein...@hotmail.com wrote:
>>>
>>>>As a user of tubular tires, I enjoy the feel
>>>
>>> Yeah, the feel is so nice. Indescribly nice in fact.
>>
>>Do you mean indescribably?
>
>Yes.
But you had trouble describing it?
Jasper
Jasper Janssen
<usenet...@jt10000.com> wrote:
>On 10 Oct 2005 11:04:54 -0700, wein...@hotmail.com wrote:
>
>>As a user of tubular tires, I enjoy the feel
>
>Yeah, the feel is so nice. Indescribly nice in fact.
Do I just have a dirty mind or does anyone else get the impression John
gets a bit, err, 'closer' to his tubs than other probably do?
Jasper
wein...@hotmail.com
Rob
wein...@hotmail.com
> I think you are not convinced of your tubular repairs. Those patched
> tires should be as good a new if you do it right. When riding alone
> on tubulars, taking two spare tires is a good precaution and they
> don't take up much space under the saddle.
Well, I'm reasonably confident about the tire not flatting. But less
confident about the tire staying put.
> > Second Q, when gluing the tire to the rim, the base tape is actually
> > glued to the rim, and a different adhesive attaches the base tape to
> > the tire casing. With a repaired tubular, the base tape has been
> > removed at least in part, and then re-glued. Doesn't that then
> > imply that the strength of the tire gluing job is only going to be
> > as good as the base tape bond?
>
> Yes, but that should be well re-secured using latex emulsion. What
> may not be apparent is that unless the wheel is side slipped with the
> wheel perpendicular to the road, there are no side forces that would
> roll the tire. This became obvious to me after a fast descent on
> which I and a friend had cornered hard and after which he got a flat.
> For the tire change, the tire practically fell off without effort.
> He recalled that this was an old dry spare tire and that his rim was
> almost devoid of glue when he mounted it. Fortunately the tire had
> globs of hardened glue that registered in the spoke sockets and
> prevented tire creep. A vector diagram of a bicycle leaned at 45
> degrees makes apparent what these forces are.
Ah, that's good information. Makes me feel better, at least. Thanks for
the links -- I've read most of them in the past, and have become
somewhat practiced in tubular repair.
> Make sure it is pure latex emulsion. It cures to a clear light tan
> rubber.
This is precisely where I'm confused. First, Velox provides "contact
cement", and not latex emulsion. Second, I believe Jevelot "Tire Life"
is a latex emulsion, but I have not had great results using this as an
adhesive. Third, I don't believe that all latex emulsions are the same,
nor are they the same as contact cement.
If this helps at all, these are Veloflex tubulars, which use a cloth
base tape, and not a rubber or rubberized one.
So, which is it? Contact cement or latex emulsion?
> http://www.magicmakers.com/retail/makeup%20nye/latex.html
But this is for attaching wigs for Halloween costumes. We're not really
talking about the same intended application. Is this a recommendation?
> For rim glue, don't use something that is so hard to separate that you
> can't change a tire without destroying the tire you are pulling off.
I've been using Continental clear rim cement. Seems strong enough.
Thanks for your kind response.
Regards,
Rob
jobst....@stanfordalumni.org
That's true but Jevelot has been gone for years. I used latex from
Jiffytex:
http://floortools.com/webapp/catalog/product/list.asp?line=B0019&C=T34
That is the same stuff with which all tubulars were put together and
had on their sidewalls. I had the stuff in pint plastic bottles just
like the ones shown on this web page. I just gave my remaining
inventory to The Bicycle Outfitter, the stuff having been bought years
ago for Wednesday evening tire patch sessions in the days of yore.
> If this helps at all, these are Veloflex tubulars, which use a cloth
> base tape, and not a rubber or rubberized one.
That is probably a savings for them and a compatibility for using non
bicycle rim glue, many of which are not latex compatible, especially
for people who want to use hard glue.
> So, which is it? Contact cement or latex emulsion?
That's your choice, but contact cement is NOT latex and latex is not a
pressure sensitive glue so it cannot be used to mount tires on a rim.
It is for tire construction and reconstruction. You can't use it to
patch tubes either because it is a water emulsion.
HTTP://www.magicmakers.com/retail/makeup%20nye/latex.html
> But this is for attaching wigs for Halloween costumes. We're not really
> talking about the same intended application. Is this a recommendation?
Latex for tire casing repair.
>> For rim glue, don't use something that is so hard to separate that
>> you can't change a tire without destroying the tire you are pulling
>> off.
> I've been using Continental clear rim cement. Seems strong enough.
That depends on what you call strong enough. As I mentioned
elsewhere, the two main problems I had over the years with tubulars
was melting rim glue on descents (braking) and base tapes wearing
through from the tire squirming on the rim. At that time, Pastali rim
cement was the best compromise. I still have some of that lying
around.
Jobst Brandt
Dave
Well, given that I get flats on the rear about 10x as much as the
front, I feel pretty safe riding with no spare and my Tufo on the back
wheel.
wein...@hotmail.com
> That's true but Jevelot has been gone for years. I used latex from
> Jiffytex:
>
> http://floortools.com/webapp/catalog/product/list.asp?line=B0019&C=T34
I was able to purchase a jar of Jevelot from Business Cycles about 2
months ago. Perhaps "new old stock". Thanks for the tip on Jiffytex.
> That is the same stuff with which all tubulars were put together and
> had on their sidewalls. I had the stuff in pint plastic bottles just
> like the ones shown on this web page. I just gave my remaining
> inventory to The Bicycle Outfitter, the stuff having been bought years
> ago for Wednesday evening tire patch sessions in the days of yore.
Just to be clear -- Jiffytex was used to re-attach the base tapes to
the tire casing?
> HTTP://www.magicmakers.com/retail/makeup%20nye/latex.html
>
> > But this is for attaching wigs for Halloween costumes. We're not really
> > talking about the same intended application. Is this a recommendation?
>
> Latex for tire casing repair.
Do you believe this is the same stuff as Jiffytex?
I went to Dow's website on "latex emulsions". I came away with the
impression that saying you want latex emulsion is like saying you want
a beer. Lots of different types.
> That depends on what you call strong enough. As I mentioned
> elsewhere, the two main problems I had over the years with tubulars
> was melting rim glue on descents (braking) and base tapes wearing
> through from the tire squirming on the rim. At that time, Pastali rim
> cement was the best compromise. I still have some of that lying
> around.
I remember reading your posts on this topic. I kind of dismissed it at
the time, but over the summer I rode down Coleman Valley Rd in Sonoma
Cty. to Hwy 1. It's a very steep decent, and I pack a few pounds. About
2/3 of the way down, I noticed the front felt "greasy". Out of
(ignorance) curiosity, I brought the bike to a stop and touched the
rim. Very nearly got blisters, the rim was so hot. Then, I noticed the
smell of the brake pads. The tire did shift on the rim as the glue
softened (Conti), but otherwise no problems. Experience is always the
best teacher. I should read Siddartha, again.
Pastalli rim cement? Could I beg a serving? -- I live in the SF bay
area.
Thanks and regards,
Rob
wein...@hotmail.com
> Well, given that I get flats on the rear about 10x as much as the
> front, I feel pretty safe riding with no spare and my Tufo on the back
> wheel.
Sounds prudent to me. I've had 3-4 flats on the rear this year. Zero on
the front.
Regards,
Rob
Lister
jobst....@stanfordalumni.org wrote:
> >> Yes, but that should be well re-secured using latex emulsion.
Ok, got the carpet latex emulsion. So how do I use it? On both
surfaces? Let dry? Or put together wet? Ok to re-cover sidewalls
also?
Thanks!
L
Qui si parla Campagnolo
wein...@hotmail.com wrote:
> As a user of tubular tires, I enjoy the feel and the ride. Generally,
> they are trouble-free, but upon occaision a puncture has been
> experienced. I mount and repair my own tubulars. Here, I have a couple
> of questions and would appreciate insight from those perhaps more
> experienced.
>
> If I have a flat on the road, I change the tire to a spare. My spare is
> normally a previously repaired tubular tire in good condition.
> Normally, I figure the ride is basically over and turn around for home.
> However, assuming the spare is inflated properly, how hard can I "push
> it"? Obviously, the concern here is rolling a tire that is not properly
> glued, yet. I'm not talking about screaming down my favorite decent at
> 50+ mph. But, if I'm 10 miles into a 30 mile ride, should I just finish
> the ride, or cruise home slowly at the most direct route?
You can continue the ride, just be careful, I use a new, preglued tubie
for a spare. The glue on it and the rim, after pumping it up to 90posi
or so, makes it hard to take off when I get home...but I reglue it.
>
> Second Q, when gluing the tire to the rim, the base tape is actually
> glued to the rim, and a different adhesive attaches the base tape to
> the tire casing. With a repaired tubular, the base tape has been
> removed at least in part, and then re-glued. Doesn't that then imply
> that the strength of the tire gluing job is only going to be as good as
> the base tape bond?
That is correct. Why, when repairing the tire, I remove the smallest
section I can. Re'attch with Fastac.
>
> For me, re-attaching the base tape has been the principal challenge in
> repairing the tubulars. I've tried "Tire Life" and that French contact
> cement that comes in the Velox kit. Neither is totally confidence
> inspiring, although the "Tire Life" on the casing and base tape seems
> to provide a better surface for the French contact cement to bond to. I
> know "latex emulsion" has been mentioned several times, but I'm not
> enough of a chemist to figure out which carpet glue at Home Depot is
> going to have properties adequate for a bicycl tire.
>
> Finally, are all contact cements created equal? What are the key
> properties of the contact cement in the Velox kit?
Don't know.
>
> Thanks and regards,
>
> Rob
Qui si parla Campagnolo
Another myth and lore about tubies...about how they somehow flat
'more'. In 20 years of riding I have 2 flats on one ride twice.....
SocSecTr...@earthlink.net
wein...@hotmail.com wrote:
> I remember reading your posts on this topic. I kind of dismissed it at
> the time, but over the summer I rode down Coleman Valley Rd in Sonoma
> Cty. to Hwy 1. It's a very steep decent, and I pack a few pounds. About
> 2/3 of the way down, I noticed the front felt "greasy". Out of
> (ignorance) curiosity, I brought the bike to a stop and touched the
> rim. Very nearly got blisters, the rim was so hot. Then, I noticed the
> smell of the brake pads. The tire did shift on the rim as the glue
> softened (Conti), but otherwise no problems. Experience is always the
> best teacher. I should read Siddartha, again.
If you are doing the kind of descending that puts that kind of stress
on your glue, you need to use the best available glue for heat
resistance, Vittoria Mastik One. It has been shown experimentally to
retain more of its bond strength at higher temperatures than any others
in common use.
It makes a pretty tight bond, so you will need a lever pry it up when
you need to change a flat. When you are changing a tire, make sure that
you don't pull the tire off by the casing, but by the base tape- that
way you don't have to worry about pulling the base tape away from the
casing. Use the lever to pry up the tire until you can get your hand
under the tire, between the base tape and the rim, and then pull up
from the rim.
And, no, I don't work for Vittoria. But the data on the superiority of
Mastik One is so crystal clear that unless someone comes up with new
data to dispute it, I can't see any good reason for using any other
glue.
jobst....@stanfordalumni.org
>> Yes, but that should be well re-secured using latex emulsion.
> Ok, got the carpet latex emulsion. So how do I use it? On both
> surfaces? Let dry? Or put together wet? Ok to re-cover sidewalls
> also?
Paint it on both surfaces, put the tire on a rim and inflate it hard.
The water content will evaporate overnight.
Jobst Brandt
David L. Johnson
> As a user of tubular tires, I enjoy the feel and the ride. Generally,
> they are trouble-free, but upon occaision a puncture has been
> experienced. I mount and repair my own tubulars. Here, I have a couple
> of questions and would appreciate insight from those perhaps more
> experienced.
>
> If I have a flat on the road, I change the tire to a spare. My spare is
> normally a previously repaired tubular tire in good condition.
> Normally, I figure the ride is basically over and turn around for home.
> However, assuming the spare is inflated properly, how hard can I "push
> it"? Obviously, the concern here is rolling a tire that is not properly
> glued, yet. I'm not talking about screaming down my favorite decent at
> 50+ mph. But, if I'm 10 miles into a 30 mile ride, should I just finish
> the ride, or cruise home slowly at the most direct route?
Heck, finish the ride. People used to finish races after replacing a flat
tire. There should be some glue adhering to the spare, so that will give
pretty good adhesion, especially after you've hit the brakes a few times.
>
> Second Q, when gluing the tire to the rim, the base tape is actually
> glued to the rim, and a different adhesive attaches the base tape to the
> tire casing. With a repaired tubular, the base tape has been removed at
> least in part, and then re-glued. Doesn't that then imply that the
> strength of the tire gluing job is only going to be as good as the base
> tape bond?
Yes, but if you use good latex it should be stronger than the rim glue.
>
> For me, re-attaching the base tape has been the principal challenge in
> repairing the tubulars. I've tried "Tire Life"
I don't know what that is. Latex emulsion is the proper stuff. It's sold
in carpet wholesalers, by the liter.
> know "latex emulsion" has been mentioned several times, but I'm not
> enough of a chemist to figure out which carpet glue at Home Depot is
> going to have properties adequate for a bicycl tire.
I have no idea what is sold at Home Depot. Go to a distributer; someone
who does only carpet. It's often called seam sealer. Check out the
smell; it should smell like latex.
AFAIK the glue in the Velox kits is to adhere the patch to the tube; it's
a vulcanizing cement, smells like airplane glue more or less. Not for
base tape.
--
David L. Johnson
__o | You will say Christ saith this and the apostles say this; but
_`\(,_ | what canst thou say? -- George Fox.
(_)/ (_) |
David L. Johnson
No manufacturer is going to recommend their glue to you. Too many lawyers
hanging around. But if you want to keep riding tubulars, you need to get
the right stuff. Don't put contact cement on the tire.
> I've been using Continental clear rim cement. Seems strong enough.
His point was --- not too strong.
--
David L. Johnson
__o | Accept risk. Accept responsibility. Put a lawyer out of
_`\(,_ | business.
(_)/ (_) |
SocSecTr...@earthlink.net
None of the road glues are too strong, but Brandt implies that if you
can't pull the tires off without the help of a lever, they are. I would
counter that if you can remove the tire _without_ a lever, or that if
tire inflation is the strongest force holding your tubular on the rim,
they are not glued on well enough.
For a person whose tires feel "greasy" on downhills, Conti is not the
_best_ solution.
Jasper Janssen
<pe...@vecchios.com> wrote:
>Jasper Janssen wrote:
>> Yeah? And if you then flat the *other* non tufo tyre?
>Another myth and lore about tubies...about how they somehow flat
>'more'. In 20 years of riding I have 2 flats on one ride twice.....
That's mighty impressive, you getting that from my post. Nobody's saying
they flat more -- but with clinchers and a patch kit, I can essentially
keep going through dozens of flats. I wouldn't LIKE it, mind you, but I
could.
Jasper
wein...@hotmail.com
Correct. I have separated the base tape during tire removal before,
unintentionally, with Conti. This last time, I got two very nice sized
blisters on my thumbs getting the punctured tire off while on the side
of the road. I'm not so sure a stronger glue would have been desired in
this case. A tire lever would have been nice...
> For a person whose tires feel "greasy" on downhills, Conti is not the
> _best_ solution.
Most of the decents around here tend to be gentle grade, high speed
affairs. i.e., I'm not using the brakes much, if at all. On this *one*
road, the decent is very steep, probably 15% grade or more, with lots
of sharp turns and switchbacks, which means the brakes need to be
pretty much ridden in order to keep the bike on the road. For extra
spice, this road also includes a couple of cattle crossings, which the
rider can either bunny hop at speed, or come to a complete stop and
walk over. This is the one and only instance in which the tire began to
slip, so far.
I consider this a rather extreme situation. Given the amount of heat
that was in the rim (the pads melted), I do wonder if Vittoria would
have performed much better. Still, it only costs a few bucks to find
out.
Donald Gillies
>If I have a flat on the road, I change the tire to a spare [
>tubular]. My spare is normally a previously repaired tubular tire in
>good condition. Normally, I figure the ride is basically over and
>turn around for home. However, assuming the spare is inflated
>properly, how hard can I "push it"?
Here's the trivial solution. Reach down with your fingers and turn
"on" the tire savers.
Note: people with idiotic recessed brake-bolt bikes need not apply!
Then finish the ride as you normally would. When my tires are
properly inflated, I've actually never had a flat when using these
devices. You will pay a small penalty in speed / performance, but
it's well worth the piece of mind.
- Don (who rode his bike today) Gillies
San Diego, CA
Donald Gillies
>If I have a flat on the road, I change the tire to a spare [
>tubular]. My spare is normally a previously repaired tubular tire in
>good condition. Normally, I figure the ride is basically over and
>turn around for home. However, assuming the spare is inflated
>properly, how hard can I "push it"?
Here's the trivial solution. Reach down with your fingers and turn
"on" the tire savers.
Note: people with idiotic recessed brake-bolt bikes need not apply!
Then finish the ride as you normally would. When my tires are
properly inflated, I've actually never had a flat when using Tire
Savers. You will pay a very small penalty in speed / performance, but
it's well worth the peace of mind.
jobst....@stanfordalumni.org
>> I remember reading your posts on this topic. I kind of dismissed
>> it at the time, but over the summer I rode down Coleman Valley Rd
>> in Sonoma Cty. to Hwy 1. It's a very steep decent, and I pack a
>> few pounds. About 2/3 of the way down, I noticed the front felt
>> "greasy". Out of (ignorance) curiosity, I brought the bike to a
>> stop and touched the rim. Very nearly got blisters, the rim was so
>> hot. Then, I noticed the smell of the brake pads. The tire did
>> shift on the rim as the glue softened (Conti), but otherwise no
>> problems. Experience is always the best teacher. I should read
>> Siddartha, again.
> If you are doing the kind of descending that puts that kind of
> stress on your glue, you need to use the best available glue for
> heat resistance, Vittoria Mastik One. It has been shown
> experimentally to retain more of its bond strength at higher
> temperatures than any others in common use.
> It makes a pretty tight bond, so you will need a lever pry it up
> when you need to change a flat. When you are changing a tire, make
> sure that you don't pull the tire off by the casing, but by the base
> tape- that way you don't have to worry about pulling the base tape
> away from the casing. Use the lever to pry up the tire until you
> can get your hand under the tire, between the base tape and the rim,
> and then pull up from the rim.
I see, this is not the feature that I hear from tubular advocates on
this forum. Their easy changeability in the event of a flat is most
often touted other than the incorrect claim they get no pinch flats,
flats that occurred often enough that the name "snake bite" was coined
in the days when we all rode tubulars. Now you even got rid of the
quick tire change advantage judging from your admonition.
Jobst Brandt
jobst....@stanfordalumni.org
>> If I have a flat on the road, I change the tire to a spare. My
>> spare is normally a previously repaired tubular tire in good
>> condition. Normally, I figure the ride is basically over and turn
>> around for home. However, assuming the spare is inflated properly,
>> how hard can I "push it"? Obviously, the concern here is rolling a
>> tire that is not properly glued, yet. I'm not talking about
>> screaming down my favorite decent at 50+ mph. But, if I'm 10 miles
>> into a 30 mile ride, should I just finish the ride, or cruise home
>> slowly at the most direct route?
> You can continue the ride, just be careful, I use a new, preglued
> tubie for a spare. The glue on it and the rim, after pumping it up
> to 90posi or so, makes it hard to take off when I get home...but I
> reglue it.
I suspect you are not using tubular glue, or at least not good glue,
because one of the design criteria is that a tire change is possible
without loss of safe tire adhesion. Repairing a flat on a clincher
certainly doesn't diminish performance unless the tire is slashed, in
which case not much will help.
>> Second Q, when gluing the tire to the rim, the base tape is
>> actually glued to the rim, and a different adhesive attaches the
>> base tape to the tire casing. With a repaired tubular, the base
>> tape has been removed at least in part, and then re-glued. Doesn't
>> that then imply that the strength of the tire gluing job is only
>> going to be as good as the base tape bond?
> That is correct. Why, when repairing the tire, I remove the smallest
> section I can. Re'attch with Fastac.
That should not be a problem if you do a good job repairing the
tubular. It is my experience that most tubulars are poorly repaired
these days from what I see and read here on this forum.
>> For me, re-attaching the base tape has been the principal challenge
>> in repairing the tubulars. I've tried "Tire Life" and that French
>> contact cement that comes in the Velox kit. Neither is totally
>> confidence inspiring, although the "Tire Life" on the casing and
>> base tape seems to provide a better surface for the French contact
>> cement to bond to. I know "latex emulsion" has been mentioned
>> several times, but I'm not enough of a chemist to figure out which
>> carpet glue at Home Depot is going to have properties adequate for
>> a bicycl tire.
Don't use contact cement. Use latex rubber solution.
>> Finally, are all contact cements created equal? What are the key
>> properties of the contact cement in the Velox kit?
Use tubular tire adhesive if you consider changing a tire on the road
a possibility. If you have a follow car, don't worry you could use
hard glue.
Jobst Brandt
Mike Krueger
jobst....@stanfordalumni.org wrote:
> I see, this is not the feature that I hear from tubular advocates on
> this forum. Their easy changeability in the event of a flat is most
> often touted other than the incorrect claim they get no pinch flats,
> flats that occurred often enough that the name "snake bite" was coined
> in the days when we all rode tubulars. Now you even got rid of the
> quick tire change advantage judging from your admonition.
I have been riding high quality tubulars exclusively for 12 or 13
years, that's about 35-40K training miles. I have had punctures, but
have never suffered an impact, or "pinch" flat, that I can recall.
Previously, when I rode clichers, I was plagued with them. When I do
get a puncture, often it is a slow leak that can be ridden on for
several miles, either all the way home or to a more convenient place to
stop to change the tire. Flats on clinchers, for whatever reason,
always seem to be more catastrophic.
Changing a tubular on the road is faster than replacing an inner tube
on a clincher. It takes me about 2 minutes to pry up a bit of the old
tire with a plastic tire lever, rip it off the rim, and then stick my
preglued spare on in its place. I inflate the tire to 120psi with a 16g
CO2 cartridge in seconds, and I'm on my way. My riding buddies, those
who ride clinchers, are always impressed and pleased at how quickly we
can get going again. When one of them flats, they must first carefully
inspect the tire carcass and find the penetrating object before they
can replace the tube, or invariably, they flat again.
I also maintain that tubulars are lighter, corner better, and ride more
comfortably than clinchers. The "cost of ownership" of the tires is a
bit higher, but many other fun hobbies (skiing, scuba diving, golf, fly
fishing, etc.) cost plenty of dough, too. That's life.
SocSecTr...@earthlink.net
wein...@hotmail.com wrote:
> I consider this a rather extreme situation. Given the amount of heat
> that was in the rim (the pads melted), I do wonder if Vittoria would
> have performed much better. Still, it only costs a few bucks to find
> out.
According to http://www.engr.ku.edu/~kuktl/bicycle/Part6.pdf Conti has
70% of the strenght of Mastik One at 60oC. Since we don't know what
temperature your rims reached, and we also don't know whether that
difference would hold at higher temperatures (there may be a
temperature above which they are both useless), it's hard to predict,
but my guess would be that Mastik One is likely to be significantly
better than Conti. Also worth noting: at 60oC Mastik One has a stronger
bond than 3M at 23oC.
wein...@hotmail.com
> 70% of the strenght of Mastik One at 60oC. Since we don't know what
> temperature your rims reached, and we also don't know whether that
> difference would hold at higher temperatures (there may be a
> temperature above which they are both useless), it's hard to predict,
> but my guess would be that Mastik One is likely to be significantly
> better than Conti. Also worth noting: at 60oC Mastik One has a stronger
> bond than 3M at 23oC.
I would guess that the rim temp exceeded 100 degrees C by a fair
amount. My hunch is that although Mastik One might be stronger than
other glues at normal to elevated temps, there is some temp beyond
which it is just as ineffective.
Regards,
Rob
wein...@hotmail.com
> 70% of the strenght of Mastik One at 60oC. Since we don't know what
> temperature your rims reached, and we also don't know whether that
> difference would hold at higher temperatures (there may be a
> temperature above which they are both useless), it's hard to predict,
> but my guess would be that Mastik One is likely to be significantly
> better than Conti. Also worth noting: at 60oC Mastik One has a stronger
> bond than 3M at 23oC.
I would guess that the rim temp exceeded 100 degrees C by a fair
SocSecTr...@earthlink.net
wein...@hotmail.com wrote:
> I would guess that the rim temp exceeded 100 degrees C by a fair
> amount. My hunch is that although Mastik One might be stronger than
> other glues at normal to elevated temps, there is some temp beyond
> which it is just as ineffective.
>From the paper, "Note that 60 oC (140 oF) is extreme and is not likely
to be experienced often. . .these measurements do show that some of the
popular adhesives do withstand high operating temperatures better than
others. These adhesives will have less likelihood of failure (roll-off)
and creep."
> My hunch is that although Mastik One might be stronger than
> other glues at normal to elevated temps, there is some temp beyond
> which it is just as ineffective.
That's certain, but what we don't know is how likely that temperature
is to be reached, or how likely it is for someone to to have a rim heat
to a temperature where the difference would be important. I would like
to see someone put a thermometer to a rim sometime and see what we're
really talking about. Brandt said something about the "snow sizzling"
on the rim, but for Alpine riding where elevation could significantly
affect the boiling point of water, even that's pretty imprecise.
jobst....@stanfordalumni.org
>> I would guess that the rim temp exceeded 100 degrees C by a fair
>> amount. My hunch is that although Mastik One might be stronger
>> than other glues at normal to elevated temps, there is some temp
>> beyond which it is just as ineffective.
> From the paper, "Note that 60 oC (140 oF) is extreme and is not
> likely to be experienced often... these measurements do show that
> some of the popular adhesives do withstand high operating
> temperatures better than others.These adhesives will have less
> likelihood of failure (roll-off) and creep."
What paper? Having had tires blow off and seeing it happen on other's
bicycles, it is not so rare for people who ride in mountains. As I
mentioned, with water inside my tubular rim that got in around the
stem hole, I generated steam that hisses like a punctured tire as I
braked for hairpin turns on a typical alpine pass.
>> My hunch is that although Mastik One might be stronger than other
>> glues at normal to elevated temps, there is some temp beyond which
>> it is just as ineffective.
If it is truly a pressure sensitive glue, as it must be for tubular
use, then it softens with heat. I don't know what racers do in the
Alps, but I had little success until I installed insulator strips on
my rims so that the tire was not glued directly on the aluminum rim.
> That's certain, but what we don't know is how likely that
> temperature is to be reached, or how likely it is for someone to to
> have a rim heat to a temperature where the difference would be
> important. I would like to see someone put a thermometer to a rim
> sometime and see what we're really talking about. Brandt said
> something about the "snow sizzling" on the rim, but for Alpine
> riding where elevation could significantly affect the boiling point
> of water, even that's pretty imprecise.
I'm working on it, that is, a circuit board is being designed to link
a pressure sensor and thermocouple to a data recorder mounted in the
wheel. The hardware for that is lying on my desk.
Jobst Brandt
jobst....@stanfordalumni.org
>> I consider this a rather extreme situation. Given the amount of
>> heat that was in the rim (the pads melted), I do wonder if Vittoria
>> would have performed much better. Still, it only costs a few bucks
>> to find out.
> According to http:
//www.engr.ku.edu/~kuktl/bicycle/Part6.pdf
> Conti has 70% of the strength of Mastik One at 60oC. Since we don't
> know what temperature your rims reached, and we also don't know
> whether that difference would hold at higher temperatures (there may
> be a temperature above which they are both useless), it's hard to
> predict, but my guess would be that Mastik One is likely to be
> significantly better than Conti. Also worth noting: at 60oC Mastik
> One has a stronger bond than 3M at 23oC.
#CONCLUSIONS:
#
# Note that 60oC is extreme and is not likely to be experienced often.
# These adhesives have all been proven to be effective under extreme
# racing conditions. Consequently, these results should not be
# construed as a recommendation against any of them. However, when
# extreme braking conditions are expected due to the course or the
# rider's talents or when racing on asphalt in extremely hot
# conditions is expected, these measurements do show that some of the
# popular adhesives do withstand high operating temperatures better
# than others. These adhesives will have less likelihood of failure
# (roll-off) and creep.
The above conclusions convince me that the person responsible for the
tests was not aware of the typical use tubular wheels undergo and that
no tire field tests were conducted to correlate test temperatures and
tire creep (around the rim) from braking, the most common cause of
tire failure resulting from high rim temperatures. Racing on "hot
asphalt" is ridiculous. Rim glue has no way of sensing pavement
temperatures, rims being air cooled by ambient atmosphere in which
they rotate.
Jobst Brandt
David L. Johnson
> I have been riding high quality tubulars exclusively for 12 or 13
> years, that's about 35-40K training miles.
I can match your miles, but it's been years since I have been "training"
for anything.
> I have had punctures, but
> have never suffered an impact, or "pinch" flat, that I can recall.
> Previously, when I rode clichers, I was plagued with them.
I have been using clinchers for ~5 years, and have yet to get a pinch
flat. What I got with tubulars were a lot of explosive sidewall failures.
Almost gave a riding buddy a heart attack once.
When I do get
> a puncture, often it is a slow leak that can be ridden on for several
> miles,
Class, why would you want to ride on a flat/soft tire for several miles?
Perhaps because you have no more spare tires?
> either all the way home or to a more convenient place to stop to
> change the tire. Flats on clinchers, for whatever reason, always seem to
> be more catastrophic.
Quite the opposite for me. With tubulars, I always carried two spares. I
occasionally also ran out. For this reason I had to carry a cell phone
"Hello, honey, can you come get me?" Tubulars always flatted more for me
than clinchers.
> Changing a tubular on the road is faster than replacing an inner tube on
> a clincher.
Changing the first, and maybe the second flat. The third??
> I also maintain that
> tubulars are lighter, corner better, and ride more comfortably than
> clinchers.
Lighter, yes. Especially when you take into account the heavier clincher
rim, and the separate tube and rim tape. Ride? never noticed a
difference. Cornering? There is no demonstrable way in which a tubular
tire can have better cornering than a clincher -- the only difference is
the way it is attached to the rim. beyond the rim, they are the same
structure. So, what about it allows it to corner better?
The "cost of ownership" of the
tires is a bit higher, but
a bit....
--
David L. Johnson
__o | Some people used to claim that, if enough monkeys sat in front
_`\(,_ | of enough typewriters and typed long enough, eventually one of
(_)/ (_) | them would reproduce the collected works of Shakespeare. The
internet has proven this not to be the case.
David L. Johnson
> #CONCLUSIONS:
> #
> # Note that 60oC is extreme and is not likely to be experienced often.
Huh? Anyone who has gone down even a short, twisty hill will brake enough
to exceed this temperature -- most will exceed 100oC. I have burned my
fingers grabbing a rim at the bottom of a hill.
--
David L. Johnson
__o | Some people used to claim that, if enough monkeys sat in front
SocSecTr...@earthlink.net
jobst....@stanfordalumni.org wrote:
> someone writes:
> #CONCLUSIONS:
> #
> # Note that 60oC is extreme and is not likely to be experienced often.
> # These adhesives have all been proven to be effective under extreme
> # racing conditions. Consequently, these results should not be
> # construed as a recommendation against any of them. However, when
> # extreme braking conditions are expected due to the course or the
> # rider's talents or when racing on asphalt in extremely hot
> # conditions is expected, these measurements do show that some of the
> # popular adhesives do withstand high operating temperatures better
> # than others. These adhesives will have less likelihood of failure
> # (roll-off) and creep.
>
> The above conclusions convince me that the person responsible for the
> tests was not aware of the typical use tubular wheels undergo and that
> no tire field tests were conducted to correlate test temperatures and
> tire creep (around the rim) from braking, the most common cause of
> tire failure resulting from high rim temperatures.
If you would drop the hyperbole, since heating a rim to the point where
the tubular creeps is not typical use, you might have a point. What
they _did_ do was correlate temperature with bond strength, defined as
force required to roll a tire off of a rim. What they have not done,
and neither have you, is measure the temperatures that may be reached
on different types of rims (bare alloy, anodized and carbon) that may
be reached in braking- specific information about how much braking
force applied for how long at what speed resulted in what rim
temperature- so that cyclists may get an idea of what the probability
is of reaching that temperature in the real world. Then, test the glues
at different temperatures within that range to see at what point they
degrade to where tire creep could become significant.
I recall you posting here that the circumstance where you were most
likely to get tire creep involved long descents on unpaved Alpine roads
that did not allow safe speeds high enough for you to benefit from air
drag as a brake. OTOH, in rather lengthy descents on heavily
switchbacked, paved mountain roads in Germany, at speeds where I would
pass cars rather than they pass me, I never to my knowledge encountered
tire creep (although that may have been a function of my relative youth
and cluelessness). Furthermore, the OP noted that they had only
encountered that "greasy tire" effect one time under particularly
extreme circumstances (and for all we know it may have been related to
the behavior of the tread compound, not the glue). So, testing at 60oC
may have some value because it is a more frequently encountered
situation, and some glues become quite weak at that temperature and
should be avoided probably even for relatively moderate riding which
requires protracted braking. Nevertheless, as I said before, I would
like to see someone put a thermometer on a rim after one of these
extreme descents, and then take that temperature back to the lab and
test the glues. Might be nice, while they're at it, to throw in some
Tufo extreme tape so we can kill that bird at the same time.
> Racing on "hot
> asphalt" is ridiculous.
Not necessarily. It could easily be 120oF for summer racing in parts of
the South and Southwest, which combined with some braking, a glue that
is particulary heat sensitive and a suboptimally mounted tire could cut
the safety margin against a rolled tire to nil.
Jasper Janssen
<david....@ptd.net> wrote:
>On Wed, 12 Oct 2005 04:43:00 -0700, Mike Krueger wrote:
>> I also maintain that
>> tubulars are lighter, corner better, and ride more comfortably than
>> clinchers.
>
>Lighter, yes.
Not with two spare tubs versus 2 spare tubes accounted for...
Jasper
Donald Gillies
>On Wed, 12 Oct 2005 22:11:56 -0400, "David L. Johnson"
><david....@ptd.net> wrote:
>>On Wed, 12 Oct 2005 04:43:00 -0700, Mike Krueger wrote:
>>> I also maintain that
>>> tubulars are lighter, corner better, and ride more comfortably than
>>> clinchers.
>>
>>Lighter, yes.
Wait a minute. Let's do a "fair" comparison.
Tubulars - 2x - on bike - 500gm (realistic, veloflex criterium)
Tubulars - 1x - as spare - 250gm
TOTAL 750 gm
Clinchers - 2x - on bike - 440gm (continental gp 4000)
Tubes - 2x - on bike - 140 gm (michelin aircomp)
Tubes - 1x - as spare - 70 gm (michelin aircomp)
Tire Spoons 3x - as spare - 100 gm
TOTAL 750 gm
Tubulars come out on top by a whopping 0 grams! Add a patch kit and
advantage probably widens to 30 grams, or almost 3% lighter !! Of
course, change the tire spoons for carbon or nylon and things get much
cloudier ...
- Don Gillies
San Diego, CA
SocSecTr...@earthlink.net
Any accounting for weight difference of rims?
Donald Gillies
>Jasper
Good point, but wait a minute. Let's do a "fair" comparison.
Tubulars - 2x - on bike - 500gm (realistic, veloflex criterium)
Tubulars - 1x - as spare - 250gm
TOTAL 750 gm
Clinchers - 2x - on bike - 440gm (continental gp 4000)
Tubes - 2x - on bike - 140 gm (michelin aircomp)
Tubes - 1x - as spare - 70 gm (michelin aircomp)
Tire Spoons 3x - as spare - 100 gm
TOTAL 750 gm
Tubulars come out on top by a whopping 0 grams! Add a patch kit and
advantage probably widens to 30 grams, or almost 3% lighter !! Of
course, change the tire spoons for carbon or nylon and hmm, i have
suddenly forgotten how to add !!
SocSecTr...@earthlink.net
If you think I must carry two spare tubulars, which I wouldn't (unless
you absolutely insist), then I think you MUST carry a spare clincher
tire to protect against the occasional complete casing failure.
Donald Gillies
>Jasper
Good point, buwt wait a minute. Let's do a "fair" comparison.
Tubulars - 2x - on bike - 500gm (realistic, veloflex criterium)
Tubulars - 1x - as spare - 250gm
TOTAL 750 gm
Clinchers - 2x - on bike - 440gm (continental gp 4000)
Tubes - 2x - on bike - 140 gm (michelin aircomp)
Tubes - 1x - as spare - 70 gm (michelin aircomp)
Tire Spoons 3x - as spare - 100 gm
TOTAL 750 gm
Tubulars come out on top by a whopping 0 grams! Add a patch kit and
advantage probably widens to 30 grams, or almost 4% lighter !! Of
course, change the tire spoons for carbon or nylon and hmmm
... suddenly I have forgotten how to add !!!
dvt
> If you think I must carry two spare tubulars, which I wouldn't (unless
> you absolutely insist), then I think you MUST carry a spare clincher
> tire to protect against the occasional complete casing failure.
Energy bar wrappers work very well for patching casing failures with
clinchers. I suspect that wouldn't work with tubies.
--
Dave
dvt at psu dot edu
SocSecTr...@earthlink.net
dvt wrote:
> SocSecTr...@earthlink.net wrote:
> > If you think I must carry two spare tubulars, which I wouldn't (unless
> > you absolutely insist), then I think you MUST carry a spare clincher
> > tire to protect against the occasional complete casing failure.
>
> Energy bar wrappers work very well for patching casing failures with
> clinchers.
No, no- I INSIST that you carry a spare tire.
> I suspect that wouldn't work with tubies.
It's irrelevant with "tubies".
David L. Johnson
True, though I do carry one spare (clincher) tire on most rides, so that
if I can't find the cause of a flat I can put on a new tire and be sure.
Also helpful if a tire casing is damaged.
--
David L. Johnson
__o | You will say Christ saith this and the apostles say this; but
_`\(,_ | what canst thou say? -- George Fox.
(_)/ (_) |
Mike Krueger
> I have been using clinchers for ~5 years, and have yet to get a pinch
> flat. What I got with tubulars were a lot of explosive sidewall failures.
> Almost gave a riding buddy a heart attack once.
How odd. I ride quality tubulars-Veloflex and Vittoria. I have never
seen or heard of a sidewall spontaneously blowing out.
> > When I do get
> > a puncture, often it is a slow leak that can be ridden on for several
> > miles,
>
> Class, why would you want to ride on a flat/soft tire for several miles?
> Perhaps because you have no more spare tires?
If I can actually make it home without having to stop to change the
tire, why wouldn't I want to do so?
I can honestly say that I have never suffered two flat tubulars on the
same ride in 13 years. If I did, one of my buddies would lend me his
spare, since many of my friends also ride tubulars. On solo rides, I'm
usually within a few miles of civilization, so I carry a cell phone
just in case.
> The "cost of ownership" of the
> tires is a bit higher, but
>
> a bit....
I find it amusing how people who wax poetic over their $6,000 bikes and
the latest, must-have carbon fiber and titanium components, are so
cheap about tires. I don't know what you spend on mortage payments,
taxes, medical care and health insurance every year, but I spend a
fortune, so a couple of hundred dollars a year for top-quality tubulars
isn't going to make or break me.
wein...@hotmail.com
> Lighter, yes. Especially when you take into account the heavier clincher
> rim, and the separate tube and rim tape. Ride? never noticed a
> difference. Cornering? There is no demonstrable way in which a tubular
> tire can have better cornering than a clincher -- the only difference is
> the way it is attached to the rim. beyond the rim, they are the same
> structure. So, what about it allows it to corner better?
The tire flexes more, allowing it to grip the road surface better.
Regards,
Rob
David L. Johnson
How can that be? I mean, the tire structure is indistinguishable between
tubular and clincher, once you move the slightest bit away from the rim,
and the road surface is better than 1/2" away from the rim. For a
similar-quality tire, the road surface and grip cannot be effected by the
difference between glue and bead attachment to the rim.
--
David L. Johnson
__o | Enron's slogan: Respect, Communication, Integrity, and
_`\(,_ | Excellence.
(_)/ (_) |
David L. Johnson
> David L. Johnson wrote:
>> I have been using clinchers for ~5 years, and have yet to get a pinch
>> flat. What I got with tubulars were a lot of explosive sidewall failures.
>> Almost gave a riding buddy a heart attack once.
>
> How odd. I ride quality tubulars-Veloflex and Vittoria. I have never
> seen or heard of a sidewall spontaneously blowing out.
Not spontaneous, but the result of damage. I found the Vittorias I used
to be prone to damage from potholes, etc., easily developing bulges from
broken threads in the casing.
> If I can actually make it home without having to stop to change the
> tire, why wouldn't I want to do so?
It depends on how far you want to ride on a flat tire, I suppose, but it
is a lot easier to ride on an inflated tire.
> I can honestly say that I have never suffered two flat tubulars on the
> same ride in 13 years.
I did. I also had 3 in a day. It was not a good day.
>> The "cost of ownership" of the
>> tires is a bit higher, but
>>
>> a bit....
>
> I find it amusing how people who wax poetic over their $6,000 bikes and
> the latest, must-have carbon fiber and titanium components, are so cheap
> about tires. I don't know what you spend on mortage payments, taxes,
> medical care and health insurance every year, but I spend a fortune, so
> a couple of hundred dollars a year for top-quality tubulars isn't going
> to make or break me.
A couple hundred a year? That is a lot of tires. What, you throw them
away when you get a flat?
--
David L. Johnson
__o | Anyone who is capable of getting themselves made President
_`\(,_ | should on no account be allowed to do the job. -- Douglas Adams
(_)/ (_) |
John Forrest Tomlinson
<david....@ptd.net> wrote:
>On Thu, 13 Oct 2005 14:39:20 -0700, Mike Krueger wrote:
>
>> David L. Johnson wrote:
>>> I have been using clinchers for ~5 years, and have yet to get a pinch
>>> flat. What I got with tubulars were a lot of explosive sidewall failures.
>>> Almost gave a riding buddy a heart attack once.
>>
>> How odd. I ride quality tubulars-Veloflex and Vittoria. I have never
>> seen or heard of a sidewall spontaneously blowing out.
>
>Not spontaneous, but the result of damage. I found the Vittorias I used
>to be prone to damage from potholes, etc., easily developing bulges from
>broken threads in the casing.
How can that be? I mean, the tire structure is indistinguishable
between tubular and clincher. Why should tubulars blow out from
damage more?
JFT
****************************
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john
"nut" end? Sorry I can't remember from when I had such a new bike. I
think both ends are recessed, but not sure. If only one end is
recessed, a tire saver could be mounted to the other end. I was
wondering if a device, similar to a bar plug that use a screw to hold
the plug in the end of the handle bar, could be devised to hold the
tire saver in the bottom of the steerer tube.
I honestly don't think that my tire savers take away any speed. I
carefully adjust them to where they just barely skim the top of the
tire. They don't need to rub hard. The type that use a flat washer at
the bolt hole are much easier to set up than the wire type shown in the
3rd Hand site.
To me the biggest down side is the extra dirt they generate. I
recently bought about a half a dozen from a bike store that had them
sitting around.
"Tire Savers Live" John
David L. Johnson
> How can that be? I mean, the tire structure is indistinguishable
> between tubular and clincher. Why should tubulars blow out from
> damage more?
Simple. The tubulars I could afford were poorly made. Dollar for dollar,
you get a better tire with a clincher, since there is a bigger market. To
get the same quality of tire in a tubular, you pay nearly double.
_Most_ tubulars these days are poorly made, and overpriced. Look at the
ads for tubulars, versus those for clinchers. Tubular ads tend to talk
about the fact that the tires are round and straight -- those are not
features, they are minimal requirements. But even that faint praise is
unjustified; many are lumpy. Clincher ads may be puffery, but at least
for $25 you can get something round and straight with no fuss.
--
David L. Johnson
__o | Arguing with an engineer is like mud wrestling with a pig... You
_`\(,_ | soon find out the pig likes it!
(_)/ (_) |
John Forrest Tomlinson
<david....@ptd.net> wrote:
>Tubular ads tend to talk
>about the fact that the tires are
> round and straight --
I haven't seen that recently -- in the last ten year or more. I'm
curious to see such an ad.
JT
vc_...@hotmail.com
David L. Johnson wrote:
> On Thu, 13 Oct 2005 14:39:20 -0700, Mike Krueger wrote:
>
> I also had 3 in a day. It was not a good day.
Ouch. That happened to me once (I only carry two spares) and I had to
put the one with the slowest leak back on to get home, pumping it up
every couple of miles or so.
I had a four tubie flats in two days (two each day) after a
particularly wet period but that is definitely rare.
Greg Hall
David L. Johnson
> On Fri, 14 Oct 2005 00:43:16 -0400, "David L. Johnson"
> <david....@ptd.net> wrote:
>
>>Tubular ads tend to talk
>>about the fact that the tires are
>> round and straight --
>
> I haven't seen that recently -- in the last ten year or more. I'm
> curious to see such an ad.
I haven't looked for a while. Let's see. Here's one with a local
connection:
The owners of the Clement name have raised the licensing fees to a point
where , uh, what exactly is the point? We're just not so sure any more. At
any, rate we'll continue to offer the exact same tire we've sold since
1995, no longer with the d'Alessandro label and no longer with the Clement
label but simply marked Servizio Corsa. They have arrived just as
straight and uniform as always. 2005 tires are black tread with natural
sidewall or all black.
http://www.yellowjersey.org/tt.html
Not to pick on Peter, but:
We first sold these wonderful tubs somewhere around 1996 and have used
tons of them ever since. We all remember good midprice tubulars and some
riders complain those days are gone. Not here! These excellent long-fiber
cotton tubulars are a zippy 290g and they run straight. I use them for my
two commuter bikes. With the normal butyl tubes I don't even check the
air sometimes for a week or two.
The picture also emphasizes that the tires are "round and straight"; see
http://www.yellowjersey.org/d'aless.html
--
David L. Johnson
__o | Anyone who is capable of getting themselves made President
jobst....@stanfordalumni.org
> If you would drop the hyperbole, since heating a rim to the point
> where the tubular creeps is not typical use, you might have a point.
> What they _did_ do was correlate temperature with bond strength,
> defined as force required to roll a tire off of a rim. What they
> have not done, and neither have you, is measure the temperatures
> that may be reached on different types of rims (bare alloy, anodized
> and carbon) that may be reached in braking- specific information
> about how much braking force applied for how long at what speed
> resulted in what rim temperature- so that cyclists may get an idea
> of what the probability is of reaching that temperature in the real
> world. Then, test the glues at different temperatures within that
> range to see at what point they degrade to where tire creep could
> become significant.
It is typical use around the SF bay area on paved roads where we have
many roads in the coast range and Santa Cruz Mountains. One of the
rituals of tubulars was to turn the front wheel around after a descent
so that the tire would creep back toward normal, the valve stem
leaning strongly from heat creep. As I related, in the Alps this was
not possible because the tire crept so much during a descent that
before expected the stem ripped out of the tube. To counter that, I
put epoxied insulator strips around all my rims.
> I recall you posting here that the circumstance where you were most
> likely to get tire creep involved long descents on unpaved Alpine
> roads that did not allow safe speeds high enough for you to benefit
> from air drag as a brake. OTOH, in rather lengthy descents on
> heavily switchbacked, paved mountain roads in Germany, at speeds
> where I would pass cars rather than they pass me, I never to my
> knowledge encountered tire creep (although that may have been a
> function of my relative youth and cluelessness).
The unpaved roads were the worst case, however descending 10% grades
on paved roads with a series of hairpin turns also caused tire
failure. It isn't easy to reverse a wheel when the rim is too hot to
touch. You have to hold it by the tire only.
> Furthermore, the OP noted that they had only encountered that
> "greasy tire" effect one time under particularly extreme
> circumstances (and for all we know it may have been related to the
> behavior of the tread compound, not the glue). So, testing at 60oC
> may have some value because it is a more frequently encountered
> situation, and some glues become quite weak at that temperature and
> should be avoided probably even for relatively moderate riding which
> requires protracted braking.
What do you mean by tread compound. Tread rubber is a good insulator
and to heat the rim means that all the air in the tire would need to
be heated, through the tread and tube, to melt rim glue. That is more
than I can take. Don't bend over backward to apologize for this
"researcher".
> Nevertheless, as I said before, I would like to see someone put a
> thermometer on a rim after one of these extreme descents, and then
> take that temperature back to the lab and test the glues. Might be
> nice, while they're at it, to throw in some Tufo extreme tape so we
> can kill that bird at the same time.
I'll give some temperature when I get them measured but I don't care
to test rim glues. I did enough of that for more than 20 years and
they all failed the test.
>> Racing on "hot asphalt" is ridiculous.
> Not necessarily. It could easily be 120oF for summer racing in
> parts of the South and Southwest, which combined with some braking,
> a glue that is particulary heat sensitive and a suboptimally mounted
> tire could cut the safety margin against a rolled tire to nil.
Yes... and how can that heat the rim to the point where the glue gets
soft?
Jobst Brandt
John Forrest Tomlinson
<david....@ptd.net> wrote:
>On Fri, 14 Oct 2005 07:03:28 -0400, John Forrest Tomlinson wrote:
>
>> On Fri, 14 Oct 2005 00:43:16 -0400, "David L. Johnson"
>> <david....@ptd.net> wrote:
>>
>>>Tubular ads tend to talk
>>>about the fact that the tires are
>>> round and straight --
>>
>> I haven't seen that recently -- in the last ten year or more. I'm
>> curious to see such an ad.
>
>I haven't looked for a while. Let's see. Here's one with a local
>connection:
>
>The owners of the Clement name have raised the licensing fees to a point
>where , uh, what exactly is the point? We're just not so sure any more. At
>any, rate we'll continue to offer the exact same tire we've sold since
>1995, no longer with the d'Alessandro label and no longer with the Clement
> label but simply marked Servizio Corsa. They have arrived just as
>straight and uniform as always. 2005 tires are black tread with natural
>sidewall or all black.
>
>http://www.yellowjersey.org/tt.html
>
Oh, you meant ads for *cheap* mention being straight. Higher quality
tubulars dont' bother mentioning that -- it's a minimal requirement
that they all have.
Mike Krueger
David L. Johnson wrote:
> On Thu, 13 Oct 2005 14:39:20 -0700, Mike Krueger wrote:
> > a couple of hundred dollars a year for top-quality tubulars isn't going
> > to make or break me.
>
> A couple hundred a year? That is a lot of tires. What, you throw them
> away when you get a flat?
I ride 3,000-4,000 mi/yr, and the roads here are often strewn with
debris, glass, and other hazards. I spend up to $50 for a Vittoria CX,
Veloflex Carbon, or comparable tubular, and if I go through 4 tires a
year due to flats or just wear, I don't consider that too outrageous. I
do get some of them fixed at TireAlert for $16 each, but I still budget
for 4 new tires a year, purchasing them on sale or closeouts when I can
get a good deal.
David L. Johnson
Well, OK, I guess, but I wouldn't consider 750-1000 miles to be good
mileage per tire (figuring that you do front-to-back, new-to-front
replacement, and essentially all wear occurs when the tire is on the
back). I get something like 3 times that mileage, even more on the
Avocets I have.
--
David L. Johnson
__o | If all economists were laid end to end, they would not reach a
_`\(,_ | conclusion. -- George Bernard Shaw
(_)/ (_) |
Mike Krueger
> On Sat, 15 Oct 2005 08:45:42 -0700, Mike Krueger wrote:
> > I ride 3,000-4,000 mi/yr, and the roads here are often strewn with
> > debris, glass, and other hazards. I spend up to $50 for a Vittoria CX,
> > Veloflex Carbon, or comparable tubular, and if I go through 4 tires a
> > year due to flats or just wear, I don't consider that too outrageous. I
> > do get some of them fixed at TireAlert for $16 each, but I still budget
> > for 4 new tires a year, purchasing them on sale or closeouts when I can
> > get a good deal.
>
> Well, OK, I guess, but I wouldn't consider 750-1000 miles to be good
> mileage per tire (figuring that you do front-to-back, new-to-front
> replacement, and essentially all wear occurs when the tire is on the
> back). I get something like 3 times that mileage, even more on the
> Avocets I have.
I don't rotate tubulars front-to-back once they are glued, but, yes,
most wear and flats do occur on the rear wheel. My rear tires do last
far longer than 1,000 mi, assuming no flats, but, as we all know, that
is more a function of luck. My routine of buying four new tires per
year to spread amongst my multiple wheelsets simply guarantees me a
safety factor of always having new spares on hand.
TireAlert can repair and refurbish punctured tubulars any number of
times, assuming no casing cuts. This also amortizes the per tire cost
downward, but I do not dispute the fact that it is much cheaper to run
clinchers. However, sometimes, the finer things in life are worth
spending a little extra money on. If I didn't think so, I'd be happy
riding my old Schwinn Continental and taking my wife out to dinner at
McDonald's every Saturday night.
Qui si parla Campagnolo
David L. Johnson wrote:
> On Thu, 13 Oct 2005 16:52:48 -0700, weinstro wrote:
>
> > David L. Johnson wrote:
> >> Lighter, yes. Especially when you take into account the heavier clincher
> >> rim, and the separate tube and rim tape. Ride? never noticed a
> >> difference. Cornering? There is no demonstrable way in which a tubular
> >> tire can have better cornering than a clincher -- the only difference is
> >> the way it is attached to the rim. beyond the rim, they are the same
> >> structure. So, what about it allows it to corner better?
> >
> > The tire flexes more, allowing it to grip the road surface better.
>
> How can that be? I mean, the tire structure is indistinguishable between
> tubular and clincher, once you move the slightest bit away from the rim,
> and the road surface is better than 1/2" away from the rim. For a
> similar-quality tire, the road surface and grip cannot be effected by the
> difference between glue and bead attachment to the rim.
>
> --
>
Think a flexible radial car tire and a bias ply tire. More of the tire
tread stays on the road during a turn with a tubular than the more
rigid and more oval clincher tire, which has to have a more rigid
sidewall to stay n the rim.
But ya know, this is old news. If ya don't like tubies, don't use them
but once again, try to recognize they are a viable tire option for
modern bicycles, as they have been at all levels of riding for almost
100 years.
David L. Johnson
> Think a flexible radial car tire and a bias ply tire.
Not really a valid comparison. The plies are indistinguishable between
tubular and clincher tires.
> More of the tire
> tread stays on the road during a turn with a tubular than the more rigid
> and more oval clincher tire, which has to have a more rigid sidewall to
> stay n the rim.
For one, no bicycle tire is oval at all. The cross-section is perfectly
round. With the exception of track tires, possibly, a comparable clincher
will have just as flexible a sidewall as a tubular.
>
> But ya know, this is old news. If ya don't like tubies, don't use them
> but once again, try to recognize they are a viable tire option for
> modern bicycles, as they have been at all levels of riding for almost
> 100 years.
Of course it's old news. But this is a technical group, and most of the
claims for tubulars are exaggerated technically. I have used both; I
still think the Clement 250-gram Criterium Seta was the best tire ever.
But over the past 30 years, clincher tires have improved immensely, and
tubulars have gone downhill. With the exception of fabulously expensive
pro racing tires, and track tires, clinchers can match or exceed tubulars,
easily, dollar for dollar, feature for feature. Well, except for weight.
--
David L. Johnson
__o | When you are up to your ass in alligators, it's hard to remember
_`\(,_ | that your initial objective was to drain the swamp. -- LBJ
(_)/ (_) |
Jasper Janssen
<david....@ptd.net> wrote:
>For one, no bicycle tire is oval at all. The cross-section is perfectly
>round. With the exception of track tires, possibly, a comparable clincher
>will have just as flexible a sidewall as a tubular.
28" x 1 3/8" x 1 5/8" on 700C tyres (ie, the actual C size, aka 37-622
nowadays) is now and has always been a complete fabrication and lie? I'll
agree that modern 37/622s are probably round, but I very much doubt that
the original size marked as 1 3/8" x 1 5/8" was circular in cross section.
Jasper
David L. Johnson
Car tires are non-round due to the steel belts and thick tread. But a
bike tire has neither of these. The casing _can't_ be other than round
since there is no mechanism other than the air pressure shaping it. The
tread is slightly built up, but only slightly except on mountain bike
tires, and even those have round casing shape.
--
David L. Johnson
__o | The lottery is a tax on those who fail to understand
_`\(,_ | mathematics.
(_)/ (_) |
Jasper Janssen
<david....@ptd.net> wrote:
>On Sun, 16 Oct 2005 21:30:29 +0000, Jasper Janssen wrote:
>> 28" x 1 3/8" x 1 5/8" on 700C tyres (ie, the actual C size, aka 37-622
>> nowadays) is now and has always been a complete fabrication and lie? I'll
>> agree that modern 37/622s are probably round, but I very much doubt that
>> the original size marked as 1 3/8" x 1 5/8" was circular in cross section.
>>
>Car tires are non-round due to the steel belts and thick tread. But a
Bias ply tyres aren't any more round than radials, though.
Jasper
David L. Johnson
> Bias ply tyres aren't any more round than radials, though.
>
It has probably been a long time since you have had bias-ply car tires, if
ever. Except for the thickness of the rubber, though, they were round --
or would be, with enough pressure in them. Bicycle tires are shaped
entirely by the air pressure, and the forces involved mean that the shape
has to be a round cross-section.
--
David L. Johnson
__o | Some people used to claim that, if enough monkeys sat in front
_`\(,_ | of enough typewriters and typed long enough, eventually one of
(_)/ (_) | them would reproduce the collected works of Shakespeare. The
internet has proven this not to be the case.
Jim Adney
wrote:
Off-hand, I don't see how it would be possible for any tire to be
anything other than round (the cord, that is, ignoring the tread)
unless the casing is belted with an inelastic belt that can constrict
the circumference of the tread.
I don't follow a lot of the modern innovations, but have there ever
been any bike tires made like this? On a single track vehicle, where
we're expected to lean, there is a marked disadvantage to an oval
tire.
Odd marked tire sizes seemed to be the norm in the old days, so I'm
not at all convinced from the numbers that a 28" x 1 3/8" x 1 5/8" was
meant to imply an oval cross section tire. It could just as well have
been a tire that fit the same rim as a 28 x 1-3/8, but with a larger
minor diameter, or the other way around. Or something completely
different....
-
-----------------------------------------------
Jim Adney jad...@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------
Jasper Janssen
>Odd marked tire sizes seemed to be the norm in the old days, so I'm
>not at all convinced from the numbers that a 28" x 1 3/8" x 1 5/8" was
>meant to imply an oval cross section tire. It could just as well have
>been a tire that fit the same rim as a 28 x 1-3/8, but with a larger
>minor diameter, or the other way around. Or something completely
>different....
It may have been the height from thread to rim versus the width from side
to side. Clincher tyres aren't circular, they're *sections* of a circle,
so...
Jasper
Qui si parla Campagnolo
David L. Johnson wrote:
>
> >
> > But ya know, this is old news. If ya don't like tubies, don't use them
> > but once again, try to recognize they are a viable tire option for
> > modern bicycles, as they have been at all levels of riding for almost
> > 100 years.
>
> Of course it's old news. But this is a technical group, and most of the
> claims for tubulars are exaggerated technically. I have used both; I
> still think the Clement 250-gram Criterium Seta was the best tire ever.
> But over the past 30 years, clincher tires have improved immensely, and
> tubulars have gone downhill. With the exception of fabulously expensive
> pro racing tires, and track tires, clinchers can match or exceed tubulars,
> easily, dollar for dollar, feature for feature. Well, except for weight.
Don't agree. A Vittoria CX, made today, is NOT exceeded by a comparibly
priced Vittoria clincher. 'Pro Racing' tires are the same ones you can
buy at any decent LBS, like ours.
'feature for feature'? Except during that finishing straight, when you
flat a clincher, and cannot finish because that soft sidewall 'Open
Tubular', comes off the rim.
SocSecTr...@earthlink.net
jobst....@stanfordalumni.org wrote:
> someone writes:
> > Furthermore, the OP noted that they had only encountered that
> > "greasy tire" effect one time under particularly extreme
> > circumstances (and for all we know it may have been related to the
> > behavior of the tread compound, not the glue). So, testing at 60oC
> > may have some value because it is a more frequently encountered
> > situation, and some glues become quite weak at that temperature and
> > should be avoided probably even for relatively moderate riding which
> > requires protracted braking.
>
> What do you mean by tread compound. Tread rubber is a good insulator
> and to heat the rim means that all the air in the tire would need to
> be heated, through the tread and tube, to melt rim glue. That is more
> than I can take.
Are you saying that tires don't heat up from friction with the road
surface as a result of hard cornering and braking, or that if they did
heat up, it would not affect the properties of the tread compound?
> Don't bend over backward to apologize for this
> "researcher".
What are you talking about? The OP has not claimed to be a
"researcher".
Donald Gillies
> With the exception of fabulously expensive pro racing tires, and
> track tires, clinchers can match or exceed tubulars, easily, dollar
> for dollar, feature for feature. Well, except for weight.
The interesting conclusion a few posts ago on this topic, is that if
you're going out for a sunday ride, tubulars and clinchers weigh the
same, because carrying a spare tubular is much heavier than carrying a
spare tube + patch kit.
- Don Gillies
San Diego, CA
SocSecTr...@earthlink.net
> Car tires are non-round due to the steel belts and thick tread. But a
> since there is no mechanism other than the air pressure shaping it.
Wrong. The weight of the rider and bicycle is also shaping the part of
the casing in contact with the pavement, which is the part we're
talking about here; furthermore, while the tube is pushing the tire
into a round shape outside the rim (where not under the weight of the
bicyclist), inside the rim the tube is pushing against the rim in
whatever shape the interior of the rim is. Only tubulars are completely
round. I think it is possible that this difference in volume (more in
clinchers) may explain why clinchers need higher air pressure to
achieve the same sidewall stiffness and prevent bottoming that causes
pinch flats.
I would like to propose a simple experiment: Take two wheels, one
tubular and one clincher, and mount tires of similar casing and width
on each. Pump up each tire with the maximum pressure that will still
allow the tire to bottom out against the rim with the same rider on the
bike in the same position (so that weight on the tire is the same). I
am hypothesizing that the clincher will require a higher pressure at
the boundary where the tire just barely flexes to the rim with a rider
on it.
A tubular, able to run at a lower pressure and therefore flex more
against the pavement, can have a larger contact patch.
Mike Krueger
> The interesting conclusion a few posts ago on this topic, is that if
> you're going out for a sunday ride, tubulars and clinchers weigh the
> same, because carrying a spare tubular is much heavier than carrying a
> spare tube + patch kit.
Translation: choose tubulars to reduce the rotating mass of your wheels
along with superior strength, handling, and comfort. Choose clinchers
to reduce the weight of your saddlebag.
David L. Johnson
> David L. Johnson wrote:
>> Car tires are non-round due to the steel belts and thick tread. But a
>> bike tire has neither of these. The casing _can't_ be other than round
>> since there is no mechanism other than the air pressure shaping it.
>
> Wrong. The weight of the rider and bicycle is also shaping the part of
> the casing in contact with the pavement, which is the part we're
> talking about here;
Is it? I thought we were talking about the profile on the rest of the
tire. Certainly the contact patch would have the same shape for either
tire.
furthermore, while the tube is pushing the tire
> into a round shape outside the rim (where not under the weight of the
> bicyclist), inside the rim the tube is pushing against the rim in
> whatever shape the interior of the rim is.
Of course, but that shape is not contributing to the ride. The difference
in volume is minimal, and the effect of either the part of the tubular
glued to the rim, or the cavity inside the rim on a clincher -- the effect
of either on the ride is negligible.
> Only tubulars are completely
> round. I think it is possible that this difference in volume (more in
> clinchers) may explain why clinchers need higher air pressure to achieve
> the same sidewall stiffness and prevent bottoming that causes pinch
> flats.
No. A clincher rim has a sharp edge, much more so than a tubular rim.
That edge, jamming into the casing of an underinflated tire (and pinching
that casing and the tube between rim and road), is what causes a pinch
flat.
>
> I would like to propose a simple experiment: Take two wheels, one
> tubular and one clincher, and mount tires of similar casing and width on
> each. Pump up each tire with the maximum pressure that will still allow
> the tire to bottom out against the rim with the same rider on the bike
> in the same position (so that weight on the tire is the same). I am
> hypothesizing that the clincher will require a higher pressure at the
> boundary where the tire just barely flexes to the rim with a rider on
> it.
>
> A tubular, able to run at a lower pressure and therefore flex more
> against the pavement, can have a larger contact patch.
Contact patch size is determined completely by tire pressure, along with
bike+rider weight and distribution. Certainly a tire at lower pressure
has a larger contact patch. How many people riding tubulars use lower
pressure than those who ride clinchers? Yeah, you have to maintain a
certain minimum with a clincher, but that minimum is less than most people
use, and most people riding tubulars use more pressure than this, too.
--
David L. Johnson
__o | I believe that the motion picture is destined to revolutionize
_`\(,_ | our educational system and that in a few years it will supplant
(_)/ (_) | largely, if not entirely, the use of textbooks -- Thomas
Edison, 1922
David L. Johnson
> Translation: choose tubulars to reduce the rotating mass of your wheels
> along with superior strength, handling, and comfort. Choose clinchers
> to reduce the weight of your saddlebag.
Look, anyone can use tubulars if they want to. Why muddle the situation
by spouting such myth and nonsense?
Yes, rotating mass (that is, mass) of wheels is lessened. But you seem to
imply that this matters more than mass on the saddlebag. No, it doesn't,
despite what the folklore is.
Superior strength, handling, and comfort? For two tires with the same
casing, the same rubber, and the same pressure, you could not tell the
difference either in terms of handling or comfort. I don't know what you
mean by the strength of a tire.
If you want to compare the handling, comfort, and durability of a $40
clincher&tube to a $60 tubular of the same weight, the clincher will
outperform the tubular. Handling and comfort are judgement calls, and it
would seem that users have a definite prejudice for their choice, but
durability is measurable. Anyone want to claim you get 3,000 miles on a
tubular tire (rear)?
--
David L. Johnson
__o | As far as the laws of mathematics refer to reality, they are not
_`\(,_ | certain, and as far as they are certain, they do not refer to
(_)/ (_) | reality. -- Albert Einstein
Jasper Janssen
>Donald Gillies wrote:
>
>> The interesting conclusion a few posts ago on this topic, is that if
>> you're going out for a sunday ride, tubulars and clinchers weigh the
>> same, because carrying a spare tubular is much heavier than carrying a
>> spare tube + patch kit.
>
>Translation: choose tubulars to reduce the rotating mass of your wheels
Canard.
>along with superior strength, handling, and comfort. Choose clinchers
Yyyeah. You did notice there was some dispute about all three factors?
>to reduce the weight of your saddlebag.
Incidentally.. do the weightweenies measure the weight of all that glue?
It's gotta add a few grams!
Jasper
Mike Krueger
> Yes, rotating mass (that is, mass) of wheels is lessened. But you seem to
> imply that this matters more than mass on the saddlebag. No, it doesn't,
> despite what the folklore is.
I don't have a PhD in physics, but I am convinced that the lower
inertia of the lighter tubular wheel is more efficient for racing and
climbing. You may not agree.
> Superior strength, handling, and comfort? For two tires with the same
> casing, the same rubber, and the same pressure, you could not tell the
> difference either in terms of handling or comfort. I don't know what you
> mean by the strength of a tire.
I was referring to the rim. A tubular rim extrusion has a higher
strength-to-weight ratio than a clincher, and is less likely to be
damaged from impacts such as potholes. Regarding comfort, this has been
discussed ad nauseum, but a tubular can be run at lower psi without
risking pinch flats. Lower pressure/more comfort, larger contact
patch/better handling.
> If you want to compare the handling, comfort, and durability of a $40
> clincher&tube to a $60 tubular of the same weight, the clincher will
> outperform the tubular. Handling and comfort are judgement calls, and it
> would seem that users have a definite prejudice for their choice, but
> durability is measurable. Anyone want to claim you get 3,000 miles on a
> tubular tire (rear)?
What is your evidence that a $40 clincher can "outperform" a $60
tubular, or that it is more durable? In many cases, manufacturers use
the identical casings for their high-end tubulars and clinchers (and
sell them for the same price).
Jasper Janssen
>David L. Johnson wrote:
>
>> Yes, rotating mass (that is, mass) of wheels is lessened. But you seem to
>> imply that this matters more than mass on the saddlebag. No, it doesn't,
>> despite what the folklore is.
>
>I don't have a PhD in physics, but I am convinced that the lower
>inertia of the lighter tubular wheel is more efficient for racing and
>climbing. You may not agree.
For steady-speed cycling, it's flatly irrelevant. For acceleration, lower
rotating mass helps a little. But on the other hand, when you're slowing
down because you're not putting out enough power to maintain speed, it's
worse. That's inertia for you. Overall weight matters in climbing and in
racing. Rotating mass, not. In fact, you don't want rotating mass to get
too small, cause it'll make the bike unstable.
It might matter a littttle bit on steep descents, come to think of it -
the kind where you essentially have to think like a racing car driver:
brake for the corner as late as possible, start accelerating again as soon
as possible, determine the ideal line to follow... Both braking and
accelerating then, rotating inertia will work against you.
Jasper
David L. Johnson
> David L. Johnson wrote:
>
>> Yes, rotating mass (that is, mass) of wheels is lessened. But you seem to
>> imply that this matters more than mass on the saddlebag. No, it doesn't,
>> despite what the folklore is.
>
> I don't have a PhD in physics, but I am convinced that the lower
> inertia of the lighter tubular wheel is more efficient for racing and
> climbing. You may not agree.
No, I don't. Climbing in particular involves, if you keep your speed up,
no change in the angular momentum of the wheel. You do have to carry it
up with you, but in that sense weight is weight. For acceleration, there
is a slight advantage, but most acceleration on a bike is not very
abrupt, so there is very little difference in energy required.
> I was referring to the rim. A tubular rim extrusion has a higher
> strength-to-weight ratio than a clincher, and is less likely to be
> damaged from impacts such as potholes.
Granted.
> Regarding comfort, this has been
> discussed ad nauseum, but a tubular can be run at lower psi without
> risking pinch flats. Lower pressure/more comfort, larger contact
> patch/better handling.
Lower pressure also means more twist of the tire in a turn, so probably
does not improve handling. But do you use lower pressure? It also
increases rolling resistance.
>
>> If you want to compare the handling, comfort, and durability of a $40
>> clincher&tube to a $60 tubular of the same weight, the clincher will
>> outperform the tubular. Handling and comfort are judgement calls, and
>> it would seem that users have a definite prejudice for their choice,
>> but durability is measurable. Anyone want to claim you get 3,000 miles
>> on a tubular tire (rear)?
>
> What is your evidence that a $40 clincher can "outperform" a $60
> tubular, or that it is more durable? In many cases, manufacturers use
> the identical casings for their high-end tubulars and clinchers (and
> sell them for the same price).
Personal experience. I could never get that sort of mileage out of a
tubular -- except for one, one of a pair of Campionato del Mundos that
lasted for thousands of miles, though it was lumpy and wrapped with tape
at the end. I regularly get 3000+ miles out of a clincher rear tire, but
never, except for that one, did I see cord before a tubular was worthless
from too many repairs.
Once you flat a tubular, it's lifespan decreases dramatically. Even with
a "professional" repair (the idea makes me chuckle a bit, though), the
casing is weakened, and the tire is not as round. Even $60 tubulars these
days have inferior casings. That del Mundo would be well over $150 today
(hand-sewn silk casing and all), but actually is not available at any
price.
As far as price/quality comparisons, Nashbar has one close-to-valid
comparison (some hype snipped from both ads):
Vittoria Open Corsa EVO-KS Racing Tire
Vittoria high quality 290 TPI casing and ... 290tpi, Kevlar
bead, 230g (700x23c). Specify 700x23 or 700x20. $39.99
Vittoria Corsa CR Tubular Tire
Real COTTON 220 TPI casing, Weight 285gm Maximum inflation 170 psi.
$49.95
Though I don't know what the casing is on the clincher, it's probably some
synthetic. From the looks of these ads I'd say the clincher was a
higher-quality tire. Less money.
--
David L. Johnson
__o | You will say Christ saith this and the apostles say this; but
_`\(,_ | what canst thou say? -- George Fox.
(_)/ (_) |
David L. Johnson
> It might matter a littttle bit on steep descents, come to think of it -
> the kind where you essentially have to think like a racing car driver:
> brake for the corner as late as possible, start accelerating again as soon
> as possible, determine the ideal line to follow... Both braking and
> accelerating then, rotating inertia will work against you.
What matters in this comparsion between tires regarding steep descents is
glue stability. Several of us, myself included, decided to chuck the
tubies in part because of trouble with glue melting on descents. Heck,
part of the downhilling technique we learned was to minimize the use of
brakes -- the fear of rolling a tire balanced out the fear of taking a
corner too fast.
The other thing that got me about tubulars was the time I tried to do a
week-long tour using them. Got new tires (d'Allesandro) just for the
trip. Still had numerous flats. Fell asleep at night with a needle in my
hand -- not from heroin use, but trying to repair a goddamn flat after a
day on the bike. Next tour, with clinchers (same diameter). No flats.
--
David L. Johnson
__o | Become MicroSoft-free forever. Ask me how.
_`\(,_ |
(_)/ (_) |
Mike Krueger
> As far as price/quality comparisons, Nashbar has one close-to-valid
> comparison (some hype snipped from both ads):
>
> Vittoria Open Corsa EVO-KS Racing Tire
> Vittoria high quality 290 TPI casing and ... 290tpi, Kevlar
> bead, 230g (700x23c). Specify 700x23 or 700x20. $39.99
>
> Vittoria Corsa CR Tubular Tire
> Real COTTON 220 TPI casing, Weight 285gm Maximum inflation 170 psi.
> $49.95
>
> Though I don't know what the casing is on the clincher, it's probably some
> synthetic. From the looks of these ads I'd say the clincher was a
> higher-quality tire. Less money.
The Vittoria Corsa EVO casing, depending on the model, is a blend of
cotton, polyester, and/or Kevlar threads coated with latex. The same
290 TPI casings are used in their highest-quality racing tires, both
tubular and clincher.
Vittoria tubulars are cheaper in GB. I mail order 'em from
ProBikeKit.com:
Vittoria Corsa EVO-KS tubular tire $39.05
Vittoria Corsa EVO-KX tubular tire $39.07
Vittoria Corsa EVO-CX tubular tire $34.61
vc_...@hotmail.com
puncture. There is also a correlation between the lifespan and the
amount of boasting about that lifespan. The more you talk about how
great the tire is, the quicker it will usually flat.
FWIW, my personally repaired racing tires become training tires as I
don't have complete faith that regluing the basetape is as good as the
factory seal.
Greg Hall
SocSecTr...@earthlink.net
David L. Johnson wrote:
> On Mon, 17 Oct 2005 11:28:57 -0700, SocSecTrainWreck wrote:
>
> > David L. Johnson wrote:
> >> Car tires are non-round due to the steel belts and thick tread. But a
> >> bike tire has neither of these. The casing _can't_ be other than round
> >> since there is no mechanism other than the air pressure shaping it.
> >
> > Wrong. The weight of the rider and bicycle is also shaping the part of
> > the casing in contact with the pavement, which is the part we're
> > talking about here;
>
> Is it? I thought we were talking about the profile on the rest of the
> tire. Certainly the contact patch would have the same shape for either
> tire.
Not if one tire were at a lower pressure, or not if one tire design
resulted in a lower sidewall stiffness at the same pressure.
> furthermore, while the tube is pushing the tire
> > into a round shape outside the rim (where not under the weight of the
> > bicyclist), inside the rim the tube is pushing against the rim in
> > whatever shape the interior of the rim is.
>
> Of course, but that shape is not contributing to the ride. The difference
> in volume is minimal, and the effect of either the part of the tubular
> glued to the rim, or the cavity inside the rim on a clincher -- the effect
> of either on the ride is negligible.
What is your proof that the difference is negligible? I think you are
making an assumption.
The cavity inside the rim of a clincher adds to the volume of the tube.
A difference of only 20% could have a significant effect on how much a
tire flattens in response to an outside force, perhaps explaining the
extra 20 psi needed in a clincher.
> > Only tubulars are completely
> > round. I think it is possible that this difference in volume (more in
> > clinchers) may explain why clinchers need higher air pressure to achieve
> > the same sidewall stiffness and prevent bottoming that causes pinch
> > flats.
>
> No. A clincher rim has a sharp edge, much more so than a tubular rim.
> That edge, jamming into the casing of an underinflated tire (and pinching
> that casing and the tube between rim and road), is what causes a pinch
> flat.
The definition of underinflated seems to be different between a
clincher and tubular, by about 20-30psi.
> Contact patch size is determined completely by tire pressure, along with
> bike+rider weight and distribution. Certainly a tire at lower pressure
> has a larger contact patch. How many people riding tubulars use lower
> pressure than those who ride clinchers?
All of them? Most of them? Would you ride a clincher at 90psi on
purpose? Is rr better at 90psi than at 110? Is cornering better?
> Yeah, you have to maintain a
> certain minimum with a clincher, but that minimum is less than most people
> use, and most people riding tubulars use more pressure than this, too.
I don't know. My impression from what I have read here is that many
people may ride tubulars at pressures that are lower than what most
people would feel secure at on clinchers. I haven't seen a
statistically valid survey, though.
David L. Johnson
>> Is it? I thought we were talking about the profile on the rest of the
>> tire. Certainly the contact patch would have the same shape for either
>> tire.
>
> Not if one tire were at a lower pressure, or not if one tire design
> resulted in a lower sidewall stiffness at the same pressure.
Sidewall stiffness is insignificant in terms of contact patch shape, since
it is so small compared to tire pressure and weight, no matter what kind
of (road) tire you have.
>> Of course, but that shape is not contributing to the ride. The
>> difference in volume is minimal, and the effect of either the part of
>> the tubular glued to the rim, or the cavity inside the rim on a
>> clincher -- the effect of either on the ride is negligible.
>
> What is your proof that the difference is negligible? I think you are
> making an assumption.
>
> The cavity inside the rim of a clincher adds to the volume of the tube.
> A difference of only 20% could have a significant effect on how much a
> tire flattens in response to an outside force, perhaps explaining the
> extra 20 psi needed in a clincher.
Highly doubtful that the difference in volume is anywhere near 20%. Look
at the spoke holes. Both a clincher and a tubular sit at the same
position relative to the spoke holes. The only real difference in
profile is the nearly vertical drop down from the bead to the base tape
on a clincher. I'd say the difference in volume is more like 5%.
On the other hand, take any wheel, and press down until it flattens out.
How much would that increase the air pressure inside the tire? Even
squished so that the rim bottoms out (which would cause a pinch flat),
that flattened area covers maybe 2-3 spokes worth of arc (staring at a
36-spoke wheel to visualize that) At most a decrease in volume of 10%,
probably less, with a comparable increase in pressure. Now, even adding
20% to the total volume would change that calculation by 2% (an 8% rather
than 10% increase in pressure). But, the amount that a force compresses
a tire depends much more on the size of the contact patch; as that
increases it creates the countering force.
Things that really bottom out a tire are sharp-edged obstructions like the
edge of a pothole or a rock. The change in volume inside the tire is far
less than from just pushing down on the wheel, so the influence of a
larger air chamber is even less significant.
I don't think most people would use 20% more air in a clincher than a
tubular of the same size. A tubular at 80psi is going to be mushy and
will feel slow. A clincher or a tubular at 100psi will be just fine for
someone my size.
> The definition of underinflated seems to be different between a clincher
> and tubular, by about 20-30psi.
30? I think that is too much.
>> pressure has a larger contact patch. How many people riding tubulars
>> use lower pressure than those who ride clinchers?
>
> All of them? Most of them? Would you ride a clincher at 90psi on
> purpose? Is rr better at 90psi than at 110? Is cornering better?
No, but I wouldn't ride a tubular at 60psi, either. I'd ride both at
100-110 psi. At 30psi below that range, the rr is considerably worse, as
is cornering.
> I don't know. My impression from what I have read here is that many
> people may ride tubulars at pressures that are lower than what most
> people would feel secure at on clinchers. I haven't seen a statistically
> valid survey, though.
Nor have I. so, tubular riders: how much pressure do you use? Anyone
(over 120 pounds, now) consistently ride below 90psi?
--
David L. Johnson
__o | It is a scientifically proven fact that a mid life crisis can
_`\(,_ | only be cured by something racy and Italian. Bianchis and
(_)/ (_) | Colnagos are a lot cheaper than Maserattis and Ferraris. --
Glenn Davies
David L. Johnson
> The Vittoria Corsa EVO casing, depending on the model, is a blend of
> cotton, polyester, and/or Kevlar threads coated with latex. The same
> 290 TPI casings are used in their highest-quality racing tires, both
> tubular and clincher.
OK, so the EVO is a better tire in both clincher and tubular than the CR.
How much would you pay for the clincher, BTW, from Britain? £21.98
Tubular: £25.94 Those were apparently the same quality tire. Closer in
price than I would have guessed, but still more for the tubular.
--
David L. Johnson
__o | It is probably that television drama of high caliber and
_`\(,_ | produced by first-rate artists will materially raise the level
(_)/ (_) | of dramatic taste in the nation. -- David Sarnoff, 1939
SocSecTr...@earthlink.net
> On Tue, 18 Oct 2005 07:54:49 -0700, SocSecTrainWreck wrote:
>
> >> Is it? I thought we were talking about the profile on the rest of the
> >> tire. Certainly the contact patch would have the same shape for either
> >> tire.
> >
> > Not if one tire were at a lower pressure, or not if one tire design
> > resulted in a lower sidewall stiffness at the same pressure.
>
> Sidewall stiffness is insignificant in terms of contact patch shape, since
> it is so small compared to tire pressure and weight, no matter what kind
> of (road) tire you have.
I guess I was not that clear. I mean sidewall stiffness as a function
of the air pressure that is stiffening it.
> Highly doubtful that the difference in volume is anywhere near 20%. Look
> at the spoke holes. Both a clincher and a tubular sit at the same
> position relative to the spoke holes. The only real difference in
> profile is the nearly vertical drop down from the bead to the base tape
> on a clincher. I'd say the difference in volume is more like 5%.
I don't think so:
d
_
/ \
|_|h
w
d=2.2
h=2.2
w=2.2
volume of a tubular tire-shaped cylinder = d*pi*(70.0*pi)
=1520cc
volume of a clincher-rim-shaped tube = ((1/2*d*pi)+(h*w))*(70.0*pi)
=1824cc
If these numbers are roughly correct, then a tubular has only 87% of
the air volume of a similarly sized clincher. I think it's remarkable
that that percentage seems to correspond so closely to the anecdotal
difference that I've seen here for the difference between min air
pressures in tubulars and clinchers.
Like I said earlier, we need to do a test that will show whether
tubulars and clinchers of the same width have the same sidewall
stiffness at the same air pressure. Anecdotal evidence suggests that
the stiffness is not the same at the same pressure, but a test like
that could put the whole thing to rest.
> On the other hand, take any wheel, and press down until it flattens out.
> How much would that increase the air pressure inside the tire? Even
> squished so that the rim bottoms out (which would cause a pinch flat),
> that flattened area covers maybe 2-3 spokes worth of arc (staring at a
> 36-spoke wheel to visualize that) At most a decrease in volume of 10%,
> probably less, with a comparable increase in pressure. Now, even adding
> 20% to the total volume would change that calculation by 2% (an 8% rather
> than 10% increase in pressure). But, the amount that a force compresses
> a tire depends much more on the size of the contact patch; as that
> increases it creates the countering force.
>
> Things that really bottom out a tire are sharp-edged obstructions like the
> edge of a pothole or a rock. The change in volume inside the tire is far
> less than from just pushing down on the wheel, so the influence of a
> larger air chamber is even less significant.
The amount of volume change itself is not that important, it is the
resistance to volume change. With a larger volume and an equal impact,
the clincher will have less resistance to volume change at the point of
impact regardless of the size of the impact.
> I don't think most people would use 20% more air in a clincher than a
> tubular of the same size.
Based on the anecdotal testimony in this ng, I think they might. 90psi
vs 110psi? Not too far-fetched, I think.
> A tubular at 80psi is going to be mushy and
> will feel slow. A clincher or a tubular at 100psi will be just fine for
> someone my size.
>
> > The definition of underinflated seems to be different between a clincher
> > and tubular, by about 20-30psi.
>
> 30? I think that is too much.
Maybe, 120psi vs 90psi? Maybe, but what about 10-20psi, 110psi vs
90psi?
> > All of them? Most of them? Would you ride a clincher at 90psi on
> > purpose? Is rr better at 90psi than at 110? Is cornering better?
>
> No, but I wouldn't ride a tubular at 60psi, either. I'd ride both at
> 100-110 psi. At 30psi below that range, the rr is considerably worse, as
> is cornering.
Try 90 vs 110, then.
> > I don't know. My impression from what I have read here is that many
> > people may ride tubulars at pressures that are lower than what most
> > people would feel secure at on clinchers. I haven't seen a statistically
> > valid survey, though.
>
> Nor have I. so, tubular riders: how much pressure do you use? Anyone
> (over 120 pounds, now) consistently ride below 90psi?
90-100. I have been using 115 on my back tire recently according to
Conti recommended pressure, but have been trying lower pressures to see
if it matters. Haven't really noticed a big difference, maybe faster
but it's hard to separate from general conditioning factors. Note that
with more weight on the back tire a differential between front and back
may be justified.
Still, the important question is: will a clincher and tubular of the
same width inflated to the same pressure have the sidewall compress the
same distance in response to the same size external force?
SocSecTr...@earthlink.net
SocSecTr...@earthlink.net wrote:
> d
> _
> / \
> |_|h
> w
> d=2.2
> h=2.2
> w=2.2
>
> volume of a tubular tire-shaped cylinder = d*pi*(70.0*pi)
> =1520cc
> volume of a clincher-rim-shaped tube = ((1/2*d*pi)+(h*w))*(70.0*pi)
> =1824cc
I looked at this and realized it's wrong, so I'll admit it before
anyone else points it out, and correct it asap.
David L. Johnson
>> > Not if one tire were at a lower pressure, or not if one tire design
>> > resulted in a lower sidewall stiffness at the same pressure.
(snip first answer)
> I guess I was not that clear. I mean sidewall stiffness as a function
> of the air pressure that is stiffening it.
But how do you think that the same pressure affects two different
sidewalls differently?
>
>> Highly doubtful that the difference in volume is anywhere near 20%.
>> Look at the spoke holes. Both a clincher and a tubular sit at the same
>> position relative to the spoke holes. The only real difference in
>> profile is the nearly vertical drop down from the bead to the base tape
>> on a clincher. I'd say the difference in volume is more like 5%.
>
> I don't think so:
> d
> _
> / \
> |_|h
> w
> d=2.2
> h=2.2
> w=2.2
>
> volume of a tubular tire-shaped cylinder = d*pi*(70.0*pi) =1520cc
> volume of a clincher-rim-shaped tube = ((1/2*d*pi)+(h*w))*(70.0*pi)
> =1824cc
>
> If these numbers are roughly correct,
Look at a clincher wheel, and think of the distance down from the rim edge
to the inner wall of the rim. It is nowhere near 2.2cm It is a small
fraction of 1 cm. Maybe 2-3mm. The rim width would also be well less
than 2.2cm, more like 1.5. Now, OTOH, there is more than a semicircle of
arc of the tire itself, but I don't think it's anywhere near enough to get
up to your numbers. Measurement time?
> Like I said earlier, we need to do a test that will show whether
> tubulars and clinchers of the same width have the same sidewall
> stiffness at the same air pressure. Anecdotal evidence suggests that the
> stiffness is not the same at the same pressure, but a test like that
> could put the whole thing to rest.
Why would the pressure be any different? You are talking about tires of
the same construction, not comparing Gatorskins to skinwall tubulars,
right?
> The amount of volume change itself is not that important, it is the
> resistance to volume change.
Huh? The resistance to volume change is given by the properties of air,
which is the same, I think, for all tires.
> With a larger volume and an equal impact,
> the clincher will have less resistance to volume change at the point of
> impact regardless of the size of the impact.
Only to the extent that the total volume is greater, about which we
disagree.
> Based on the anecdotal testimony in this ng, I think they might. 90psi
> vs 110psi? Not too far-fetched, I think.
I'll wait for the poll numbers, but I know that, for me, a 90psi tubular
was just as mushy as a 90psi clincher.
> Maybe, 120psi vs 90psi? Maybe, but what about 10-20psi, 110psi vs 90psi?
Actually, some of the tubular ads talk about very high max pressures, so
it would probably be a concern to users. One thing a tubular can do is
handle very high pressure without worrying about the strength of the rim.
I bet most tubular users use higher, not lower, pressure than most
clincher users on the same ride.
> Still, the important question is: will a clincher and tubular of the
> same width inflated to the same pressure have the sidewall compress the
> same distance in response to the same size external force?
I would say so. Can't do the experiment, though, since I gave away my
tubular rims and tires years ago.
--
David L. Johnson
__o | Some people used to claim that, if enough monkeys sat in front
Mike Krueger
David L. Johnson wrote:
> OK, so the EVO is a better tire in both clincher and tubular than the CR.
> How much would you pay for the clincher, BTW, from Britain? £21.98
> Tubular: £25.94 Those were apparently the same quality tire. Closer in
> price than I would have guessed, but still more for the tubular.
You forgot to include the separate inner tube in the cost of the
clincher tire.
SocSecTr...@earthlink.net
David L. Johnson wrote:
> Look at a clincher wheel, and think of the distance down from the rim edge
> to the inner wall of the rim. It is nowhere near 2.2cm It is a small
> fraction of 1 cm. Maybe 2-3mm. The rim width would also be well less
> than 2.2cm, more like 1.5. Now, OTOH, there is more than a semicircle of
> arc of the tire itself, but I don't think it's anywhere near enough to get
> up to your numbers. Measurement time?
Corrected:
r
_
/ \
|___|h
w
r=1.1
h=1.1
w=2.2
volume of a tubular tire-shaped cylinder = r^2*pi*(70.0*pi)
836cc
volume of a clincher-rim-shaped tube = (.5r^2*pi+h*w)*70.0*pi
950cc
Note that even in my original botched version I didn't claim 2.2 as the
distance from the edge of the rim to the base tape, but only 1.1. I
think it's a decent approximation. Nevertheless, my re-do reduces the
difference in volume to about 12%. It would be interesting to measure
it; even if you are right about the real value being only 5% I wouldn't
be convinced that it is insignificant. We are arguing here about
whether the difference in volume could explain an effect you claim
doesn't exist: that an equivalent clincher will bottom out more easily
than a clincher running at the same pressure.
I would note BTW that under pressure a tubular has a smaller volume
than a circular cylinder, that the rim pushes the base tape into the
interior of the tire and reduces the volume.
jobst....@stanfordalumni.org
>>>> Is it? I thought we were talking about the profile on the rest of the
>>>> tire. Certainly the contact patch would have the same shape for either
>>>> tire.
>>> Not if one tire were at a lower pressure, or not if one tire
>>> design resulted in a lower sidewall stiffness at the same
>>> pressure.
>> Sidewall stiffness is insignificant in terms of contact patch
>> shape, since it is so small compared to tire pressure and weight,
>> no matter what kind of (road) tire you have.
> I guess I was not that clear. I mean sidewall stiffness as a
> function of the air pressure that is stiffening it.
Could you define what "sidewall stiffness" is and how it is measured
or sensed? How would tires of the same cross section compare at the
same pressure, considering that the bending stiffness of sidewalls is
close to nothing.
>> Highly doubtful that the difference in volume is anywhere near 20%.
>> Look at the spoke holes. Both a clincher and a tubular sit at the
>> same position relative to the spoke holes. The only real
>> difference in profile is the nearly vertical drop down from the
>> bead to the base tape on a clincher. I'd say the difference in
>> volume is more like 5%.
> I don't think so:
> d
> _
> / \
> |_|h
> w
> d=2.2
> h=2.2
> w=2.2
> volume of a tubular tire-shaped cylinder = d*pi*(70.0*pi)
> =1520cc
> volume of a clincher-rim-shaped tube = ((1/2*d*pi)+(h*w))*(70.0*pi)
> =1824cc
How do you arrive at these equations? For equal tire width, both
kinds of tires have practically the same volume of air while the part
of the tire not constrained by rim contact is identical. The portion
of a tubular tire that makes contact with the rim my just as well be
attached to a bead hooked into a clincher rim for all practical
purposes.
> If these numbers are roughly correct, then a tubular has only 87% of
> the air volume of a similarly sized clincher. I think it's
> remarkable that that percentage seems to correspond so closely to
> the anecdotal difference that I've seen here for the difference
> between min air pressures in tubulars and clinchers.
I think that takes some more explanation, first why you believe there
is a difference in air volume and secondly why that would have some
effect which you do not identify here. The pressure in a tire is not
altered by load on the wheel. That has been explained in this thread
a few times. It is an old question about how much pressure should be
in the spare tire in a car, considering it is not under load of the
car when in storage. The answer is "the same as if it were on the
car" because that has no practical effect on inflation pressure.
> Like I said earlier, we need to do a test that will show whether
> tubulars and clinchers of the same width have the same sidewall
> stiffness at the same air pressure. Anecdotal evidence suggests that
> the stiffness is not the same at the same pressure, but a test like
> that could put the whole thing to rest.
What stiffness are you talking about and how do you measure it?
Compliance of the tire is only dependent on inflation pressure and
cross sectional diameter. Whether there is a huge pressure reservoir
attached to the valve stem or not makes no difference.
>> On the other hand, take any wheel, and press down until it flattens
>> out. How much would that increase the air pressure inside the
>> tire? Even squished so that the rim bottoms out (which would cause
>> a pinch flat), that flattened area covers maybe 2-3 spokes worth of
>> arc (staring at a 36-spoke wheel to visualize that) At most a
>> decrease in volume of 10%, probably less, with a comparable
>> increase in pressure. Now, even adding 20% to the total volume
>> would change that calculation by 2% (an 8% rather than 10% increase
>> in pressure).
Inflation pressure does not increase measurably even with such a
flattening load, so this whole discussion is based on a false premise
of varying inflation pressure.
>> But, the amount that a force compresses a tire depends much more on
>> the size of the contact patch; as that increases it creates the
>> countering force. >> Things that really bottom out a tire are
>> sharp-edged obstructions like the edge of a pothole or a rock. The
>> change in volume inside the tire is far less than from just pushing
>> down on the wheel, so the influence of a larger air chamber is even
>> less significant.
Well that's one way to approach it but more precisely it is the shape
of the compressed zone of the tire as is explained in:
http://www.sheldonbrown.com/brandt/rim-support.html
> The amount of volume change itself is not that important, it is the
> resistance to volume change. With a larger volume and an equal
> impact, the clincher will have less resistance to volume change at
> the point of impact regardless of the size of the impact.
You are surmising this under an inaccurate model, one of varying
inflation pressure in spite of explanations why this is not so.
>> I don't think most people would use 20% more air in a clincher than
>> a tubular of the same size.
> Based on the anecdotal testimony in this ng, I think they
> might. 90psi vs 110psi? Not too far-fetched, I think.
That's not reasonably sound science.
>> A tubular at 80psi is going to be mushy and will feel slow. A
>> clincher or a tubular at 100psi will be just fine for someone my
>> size.
>>> The definition of underinflated seems to be different between a
>>> clincher and tubular, by about 20-30psi.
>> 30? I think that is too much.
> Maybe, 120psi vs 90psi? Maybe, but what about 10-20psi, 110psi vs
> 90psi?
Maybe, maybe, maybe... That's too much conjecture to support yuor
belief.
Jobst Brandt
Michael Press
<1129647289.1...@g47g2000cwa.googlegroups.com>,
SocSecTr...@earthlink.net wrote:
>
> Not if one tire were at a lower pressure, or not if one tire design
> resulted in a lower sidewall stiffness at the same pressure.
There is no side wall stiffness. If you think there is,
provide a detailed definition. The side walls on all my
tires are as stiff as a lettuce leaf.
--
Michael Press
David L. Johnson
True. You could add a pound for that, or presume that a tube might
outlast a tire --- of course, it might be the other way around. With a
tubular, the tire life would be the minimum of tube life or rest-of-tire
life, unless you want to replace the tube, which is not for the faint of
heart (of course, you can pay someone else $16.95 plus shipping (can't
convert that to pounds) to replace the tube for you, which is a bit more
than a clincher tube).
--
David L. Johnson
__o | "Business!" cried the Ghost. "Mankind was my business. The
_`\(,_ | common welfare was my business; charity, mercy, forbearance,
(_)/ (_) | and benevolence, were, all, my business. The dealings of my
trade were but a drop of water in the comprehensive ocean of my
business!" --Dickens, "A Christmas Carol"
Jim Adney
>jobst....@stanfordalumni.org wrote:
>> What do you mean by tread compound. Tread rubber is a good insulator
>> and to heat the rim means that all the air in the tire would need to
>> be heated, through the tread and tube, to melt rim glue. That is more
>> than I can take.
>
>Are you saying that tires don't heat up from friction with the road
>surface as a result of hard cornering and braking, or that if they did
>heat up, it would not affect the properties of the tread compound?
I think he's just saying that there's insufficient thermal
conductivity between the tread and the rim glue for heat transfer from
this source to have any effect on the rim glue. I agree.
-
-----------------------------------------------
Jim Adney jad...@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------
Jasper Janssen
<david....@ptd.net> wrote:
>True. You could add a pound for that, or presume that a tube might
*One* pound? 2 at a minimum, and 4 is more like it. Which eats the
difference right there.
Jasper
David L. Johnson
4 pounds for a tube? You should buy them in the States. I can usually
get them for $2. I get a lot free on rides from those who are too proud
to repair a flat one.
--
David L. Johnson
__o | "What am I on? I'm on my bike, six hours a day, busting my ass.
_`\(,_ | What are you on?" --Lance Armstrong
(_)/ (_) |