do kelvar belts stop flats?
Alan Fairley
Hello, all. I'm back with yet another commuter tire question. DO
kelvar belts really help stop flats? I see the Vittoria Techno Twin K
has a kelvar belt and the wire bead version is about the same price as
the Conti Super Sport. Comments?
Thanks for patience with endless stream of Qs.
Alan
Garry Lee
They do substantially reduce punctures but the best solution is to
get Continental Top TOuring. These hardly ever puncture.
S. A. Maas
In my experience, they are very helpful. We (in S. California) have a lot
a debris in streets, and no-good kids who like to break bottles on bike
paths (usually in an underpass, where it's hard to see). Whe I switched
to Kevlar tires, the flats decreased from one every 2-3 outings to almost
nothing.
--
* ------------------------------------------- *
* Stephen Maas, Ph.D., PE s.m...@ieee.org *
* http://www.concentric.net/~smaas *
* Nonlinear Technologies, Inc. *
* PO Box 7284, Long Beach, CA 90807, USA *
* ------------------------------------------- *
Kelly Lopez File
Alan Fairley wrote:
>
> Hello, all. I'm back with yet another commuter tire question. DO
> kelvar belts really help stop flats? I see the Vittoria Techno Twin K
> has a kelvar belt and the wire bead version is about the same price as
> the Conti Super Sport. Comments?
>
> Thanks for patience with endless stream of Qs.
>
> Alan
I had a lot of flats on my road bike (I ride in town a lot where there
is lots of glass and debris), until I got the combination of
Continental touring tires and (most importantly) Mr. Tuffy's. The
Tuffy is a hard plastic strip that you place inside your tire so it
acts as a barrier between the tube and anything that tries to penetrate
the tire. Since I started using them, I have not had a flat for 18
months.
The Tuffy's cost about $12-15 bucks, and come in widths to fit any
size mountain or road bike tire. Ask about them at your bike shop.
They are worth their weight in gold.
--Kelly
Mike Garrison
Kelly Lopez File wrote:
>
> The Tuffy's cost about $12-15 bucks, and come in widths to fit any
> size mountain or road bike tire. Ask about them at your bike shop.
> They are worth their weight in gold.
They weigh about as much as gold, too. Still, I use 'em. I have not had
a flat in 4 years on a Mr. Tuffy protected tire, except for one where a
broken spoke led to a puncture from the inside of the rim.
I consider the extra weight (on the outside edge of the tire, the very
worst place to add weight!) as just "a better workout."
-Mike
dPoleshuck
One problem with Kevlar that I have found is that although they stofp
flats they are super hard to change (especially in the winter when
your hands are cold).
Could people comment on each type of "flat-proof" tire as to their
ease of changing.
I have been using Specialized Armadillos for many thousands of miles
and they are very flat resistant but a bear to change. I did try some
kind of Hutchinsons--also kevlar--which were supposed to be easier to
change but weren't. They also gave me three flats in the first 500
miles!
How do the Conti Top Touring and the Green Stripe Vittorias compare on
difficulty to change?
Thanks
___________________
Dave Poleshuck
Jobst Brandt
Alan Fairley wrote:
> Hello, all. I'm back with yet another commuter tire question. Do
> Kevlar belts really help stop flats?
I am not convinced they do, not from my own experience but from
observing those who believe so. I am not plagued by flats to the
degree that I choose to add rolling resistance to my tires with
inserts or Kevlar in the casing. These tires have at least 30% more
rolling resistance than the same tire without the Kevlar.
If the Kevlar prevents flats, then we should find cuts in the tread
that contain glass slivers, or just cuts for that matter, but I have
not seen such evidence. Kevlar does not stop thorns nor do Mr Tuffys.
There are those who swear by Kevlar and inserts, and there are even
more flat prone people who swear by airless tires with solid (foam)
tubes that have several times the rolling resistance of regular tires.
Somehow these pursuits seem to ignore that the majority of riders who
also ride many more miles than they, survive without these "aids" to
the extent that their flat tires are not even an issue. Therefore, I
believe the problem lies with the rider, not with the tires. I have
often felt that the flat tire folks are probably ones that don't find
money and tools on the road as others do, because the don't see them.
They also ride over anything lying in the road. What you don't see
can cause flats.
Jobst Brandt <jbr...@hpl.hp.com>
Eric Salathe
Jobst Brandt wrote:
>
> Alan Fairley wrote:
>
> > Hello, all. I'm back with yet another commuter tire question. Do
> > Kevlar belts really help stop flats?
>
> I am not convinced they do, not from my own experience but from
>
> If the Kevlar prevents flats, then we should find cuts in the tread
> that contain glass slivers, or just cuts for that matter, but I have
> not seen such evidence.
Welcom back Jobst! I agree and disagree. I have used both kevlar-belted
(IRC Roadwinner, Avocet Road) and unbelted tires (IRC Tandem, Tom Slick,
Continental SS Ultra) and cannot claim to find any systematic difference
in the nuber of flats on either type. I get very few flats with either
type (now that I inflate the tandem tires hard enough).
However, I have found numerous glass shards embedded in tire treads that
did not penetrate the casing or kevlar belt. I suspect that a good
casing can prevent small bits of glass from getting to the tube even if
it cuts the tread. Large sharp objects (like broken bottles) seem to cut
through any tire, but these are possible to avoid. What cannot be seen
and seems to get through anything are the wires from steel belted
radials.
--
,
Eric P. Salathe, Jr. sal...@atmos.washington.edu
Seattle WA
Charles R Schroeder
My experience is flats as caused by the wires from steel belted tires. Kevlar
belted or not these wires seem to penetrate anything. Thankfully they cause
slow leaks. They also seem to be more concentrated along heavily traveled
highways, avoid these roads. I'm using Specialized Armadillos now, not kevlar
belted but some kind of plastic belt. I want to see if these tires resist the
wire punctures.
In message <33DE75...@u.washington.edu> - Eric Salathe
<sal...@u.washington.edu>Tue, 29 Jul 1997 15:58:41 -0700 writes:
:>
:>Jobst Brandt wrote:
:>>
:>through any tire, but these are possible to avoid. What cannot be seen
Robert Adelman
>They weigh about as much as gold, too. Still, I use 'em. I have not had
>a flat in 4 years on a Mr. Tuffy protected tire, except for one where a
>broken spoke led to a puncture from the inside of the rim.
We just had a flat on our tandem, where a small piece of glass
penetrated the *edge* of our Mr. Tuffy; it did not pass through the
black central portion. This was a first!
Bob Adelman
jamesB
30% more rolling resistance!!!!!!
Thank God Jobst is back to keep us newbie's straight...I was just going
to run out and
buy Mr Tuffys for my commuter bike till I read Jobst's reply. Jeez,
30%, damn I'd never
get to work on time!
james
*****remove nosspam to reply*******
Jobst Brandt wrote:
> Alan Fairley wrote:
>
> > Hello, all. I'm back with yet another commuter tire question. Do
> > Kevlar belts really help stop flats?
>
> I am not convinced they do, not from my own experience but from
> observing those who believe so. I am not plagued by flats to the
> degree that I choose to add rolling resistance to my tires with
> inserts or Kevlar in the casing. These tires have at least 30% more
> rolling resistance than the same tire without the Kevlar.
>
>
>
> Jobst Brandt <jbr...@hpl.hp.com>
Ray Bowman
>My experience is flats as caused by the wires from steel belted tires.
Kevlar
>belted or not these wires seem to penetrate anything. Thankfully they
cause
>slow leaks. They also seem to be more concentrated along heavily traveled
>highways, avoid these roads. I'm using Specialized Armadillos now, not
kevlar
>belted but some kind of plastic belt. I want to see if these tires resist
the
>wire punctures.
Bike shop personnel, quite a few, l have indicated that about 90% or more
of punctures are small - creating holes (slits, actually) about 1 mm or
less in size. A good sealant will be nearly 100% effective against such
punctures, so I think you would be much better off using a sealant. I
have tested Armadillos by pushing goathead thorns into them by hand - 8
out of10 went through. Good luck, Eric - you will need it.
Ray
Sheldon Brown
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Jobst Brandt wrote:
> ...I believe the problem lies with the rider, not with the tires. I
> have
> often felt that the flat tire folks are probably ones that don't find
> money and tools on the road as others do, because the don't see them.
> They also ride over anything lying in the road. What you don't see
> can cause flats.
I suspect that, in addition, many of those who suffer most from flats
are those who timidly hug the curb. The gutter is where most of the
glass and other sharp stuff winds up.
If you ride a bit farther from the curb, you enter the section of the
roadway that gets swept by the right tires (or left tyres) of motor
traffic. You also increase your safety by making yourself more visible
and providing a bit more maneuvering room for yourself.
Sheldon "I've Got A Great Collection Of Road-Find Tools, Not To Mention
My Helmet Ornament" Brown
Newtonville, Massachusetts
+-----------------------------------+
| Habit is the nursery of errors. |
| --Victor Hugo |
+-----------------------------------+
http://www.sheldonbrown.com/harris
Harris Cyclery, West Newton, Massachusetts
(617) 244-1040 FAX 244-1041
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dPoleshuck
Jobst Brandt wrote:
> I
>believe the problem lies with the rider, not with the tires. I have
>often felt that the flat tire folks are probably ones that don't find
>money and tools on the road as others do, because the don't see them.
>They also ride over anything lying in the road. What you don't see
>can cause flats.
>
That's right, folks, it's your fault if you get a flat, (if your bike
breaks etc). Jobst is back and as stupid and nasty as ever.
Oh, Jobst how much of your money do you make testifying for
manufacturer's that it is the riders fault if something breaks?
I rode almost 8,000 miles in the past year, many of them commuting
through Staten Island, Manhattan and Brooklyn. For about four months a
year any flat is one too many. When you're avoiding cars and in the
rain you can't look for glass. Where do you commute to? When do you
ride and why are you so nasty and such an asshole?
If we are to encourage people to really ride, then bikes must exist at
all levels of ease of use (and safety) including as flat-resistant as
possible.
________________________
Dave "who never sent a flame before" Poleshuck
dave...@erols.com
m...@unixfe.cc.rl.ac.uk
dPoleshuck (dave...@erols.com) wrote:
: Could people comment on each type of "flat-proof" tire as to their
: ease of changing.
FWIW, I have not found Conti-Top-touring (700-32s)
particularly difficult to change (but then, you
don't get much practice changing them, fortunately).
Mark Freedman
fwiw I had a leak caused by glass shards which embedded in the tire,
eventually worked through to the tube. I located them by locating the
hole in the tube and using that to find the slit in the tire, pried out
(I thought) all the shards (clear glass, joy-oh-joy), installed a new
tube, and rode for several weeks until the remaining shard(s) found their
way through the new tube.
Glass shards are interesting, in that they're very hard to see, and
hard to pick out of the tire casing. Also, they only protrude into the
tube under pressure (as when riding), so feeling around inside the tire
doesn't necessarily prove their absense.
I'm not sure that sealant would be ideal in this case. Does it leave
an easy-to-find hole (sealed) in the tube ? Does it keep sealing and
sealing as each bit of glass finds its way through the tube ?
I'm thinking that a patched tube might have been more resistant to
repuncturing at the same spot (thicker rubber at the patch), but I tend
to spend the $2 rather than mess around with leaky tubes.
Not sure how Kevlar does against glass. Comments ?
Ray Bowman (rayb...@aol.com) wrote:
: >My experience is flats as caused by the wires from steel belted tires.
: Ray
--
I've had it with MyLife 1.0. When will MyLife 1.01 be out ?
Tim McNamara
Since Kevlar is a filament, woven into a strip of fabric which is placed
under the tread of the tire, I suspect that glass shards, small bits of
Michelin wire, etc could simply push between the strands just like a
needle through cloth. Since that is almost always the type of puncture
cyclists deal with, except for pinch flats (which Kevlar can't do anything
about), I would guess that Kevlar really isn't very useful in preventing
flats. It makes great beads in clinchers, however.
An effective barrier against the type of punctures cyclists deal with
would have to be a molded or extruded solid, perhaps some kind of
plastic. I would expect tis to be rather heavy and to have a negative
effect on the feel of the tire on the road (by stiffening the casing).
Tim
--
One pane of glass in the window. No one is complaining, though,
come in and shut the door. Faded is the crimson of the ribbons
that she wore, and it's strange how no one comes round any more.
-Robert Hunter
Jim Chinnis
jbr...@hpl.hp.com (Jobst Brandt) wrote in part:
>These tires have at least 30% more
>rolling resistance than the same tire without the Kevlar.
Any idea why that might be? Any data anywhere? Seems hard to believe.
The footprint will be almost the same at the same pressure and loading
for the K and non-K tires.
--
If replying by email, use the following address without the X:
Jim Chinnis Xjch...@earthlink.net Manassas, VA USA
David Wiesenhahn
In article <5rlmui$7...@hplms2.hpl.hp.com>, jbr...@hpl.hp.com (Jobst
Brandt) wrote:
>Kevlar does not stop thorns nor do Mr Tuffys.
From my experience, Mr. Tuffys can stop thorns. The best example was last
summer, when I found a large thorn had penetrated my tire, but had been
stopped by the thick black part of the Mr. Tuffy. If I didn't have the Mr.
Tuffy strip, it would've been an instantaneous flat.
This does not mean that they will prevent all flats. Whether or not they
are worth the extra weight and increased rolling resistance is another
issue. When I became less serious about racing, I removed my Mr. Tuffys.
-------------------------------------------------
Dave Wiesenhahn IDA
mailto:dwie...@ida.org Alexandria, VA
Ray Bowman
>jbr...@hpl.hp.com (Jobst Brandt) wrote in part:
>
>>These tires have at least 30% more
>>rolling resistance than the same tire without the Kevlar.
>
>Any idea why that might be? Any data anywhere? Seems hard to believe.
>The footprint will be almost the same at the same pressure and loading
>for the K and non-K tires.
I believe Jobst has measured such differences for Kevlar belted tires.
And tire liners have been measured by Dr Kyle to roughly double the
rolling resistance for road tires. Flexing of stiffer membranes generally
involves more energy loss - particularly when there is internal scuffing
between layers (likely true for tire liners).
Why not use sealants instead? They work better and have negligible effect
on rolling resistance. Solar car racers, who typically test the #%@$ out
of their components, determined sealants to be the best choice among all
flat protection schemes.
Ray
Eric Edwards
On 4 Aug 1997 12:33:15 GMT, Ray Bowman <rayb...@aol.com> wrote:
>Why not use sealants instead? They work better and have negligible effect
>on rolling resistance. Solar car racers, who typically test the #%@$ out
>of their components, determined sealants to be the best choice among all
>flat protection schemes.
I can't speak catagorically for all sealants but I used a Airlock tube
in the back tire of my commuting bike for a couple of months last
winter. I was not impressed.
It *never* sealed a flat. At best it slowed down the leak, maybe
enough to get home. Even that was uncertain. I would lose probably
40lbs pressure before the sealant started to do anything.
The only hole the sealant ever successfully plugged was the valve stem.
That was not fun.
This was a 700x25 tire inflated to about 110lbs. Your mileage may vary,
especially with low pressure MTB tires.
Jobst Brandt
Ray Bowman writes:
> Why not use sealants instead? They work better and have negligible effect
> on rolling resistance. Solar car racers, who typically test the #%@$ out
> of their components, determined sealants to be the best choice among all
> flat protection schemes.
Sealants have another hazard that the makers of the stuff are
apparently not aware. A slimy substance inside the tube will make a
bicycle uncontrollable in the event the tire goes flat from a cut,
something sealant will not block. I have had the experience, and was
fortunate that it occurred on a straight road with almost no crown. I
slid all over, controlling something as benign as a rear tire flat.
You might want to try how well an inner tube full of this stuff glides
sideways before committing yourself to it.
Jobst Brandt <jbr...@hpl.hp.com>
hau...@mbi.org
In article <5s5f01$m...@hplms2.hpl.hp.com> jbr...@hpl.hp.com (Jobst Brandt) writes:
>>> `These tires have at least 30% more rolling resistance than the
>>> same tire without the Kevlar.
>> Any idea why that might be? Any data anywhere? Seems hard to believe.
>> The footprint will be almost the same at the same pressure and loading
>> for the K and non-K tires.
>From your question it seems that you believe that rolling resistance
>is a function of contact patch size and its scrubbing on the road.
>This is what was behind the raised center ridge Specialized Touring II
>tires that had minimal road contact but high rolling resistance
Oops. Jobst, the formula for contact area is X / Y, where X = load on the
tire, and Y = air pressure in tire. Pretty simple, and it doesn't vary
depending on the tire!
As I recall, the main purpose of the center ridge was to extend tire life,
which it did. At the time they were tested as having LOWER than average
rolling resistance.
>Kevlar and especially Mr Tuffys are like molasses for the tire and
>make it absorb ore energy when it deforms.
I agree with Jobst here, although 30% definitely sounds high. Given no
definitive empirical evidence to the contrary, though, I'll take his word for
it, so long as it's legitimate testing data, not just a figure off the top of
his head.
Rich
Alan Fairley
>Jim Chinnis writes:
>
>>> `These tires have at least 30% more rolling resistance than the
>>> same tire without the Kevlar.
>
How does the 30% manifest in real life? For instance, if I can time
trial 10 miles in 1/2 hr, (actually, I wish!) how far would I go if
I was riding Kelvar belted with 30% more rolling resistance?
For that matter, how much more rolling resistance will I get if I move
from a 20 to 23 width tire. Or if I reduce inflation from 110 psi to
100 psi.
Thanks for any info here.
Alan Fairley
trad...@rocketmail.com
In article <5s5rk6$9...@hplms2.hpl.hp.com>,
jbr...@hpl.hp.com (Jobst Brandt) wrote:
> Sealants have another hazard that the makers of the stuff are
> apparently not aware. A slimy substance inside the tube will make a
> bicycle uncontrollable in the event the tire goes flat from a cut,
> something sealant will not block.
I'm not sure I can agree with Jobst on this one.
IMHO, bikes with suddenly deflated tires have no lateral
control at the wheel with the flat tire, sealant or no
sealant. The severity seems related to the speed you're
going more than anything else.
Mick.
-------------------==== Posted via Deja News ====-----------------------
http://www.dejanews.com/ Search, Read, Post to Usenet
trad...@rocketmail.com
Sorry, Rich. Jobst is right. Tire pressure and vertical force
determine the area of the tire casing involved in supporting
the load. This area is often, but not always, identical to the
contact area with the road surface. For example, farm tractors
with 25psi in the tires can dig right into warm asphalt, because
the tread pattern allows about 1/5 the contact area of a smooth
tire, causing contact pressure at the pavement to exceed 100psi.
When a bike tire has a tall, 1/8 in. (3mm) wide center
ridge, like the first Touring II, the tire casing deforms around
the ridge, much like when you ride over a stone. The result is
a smaller contact area between rubber and pavement, with increased
rolling resistance due to increased casing deformation.
In the mid-80s, Chester Kyle announced that the raised ridge tires
he tested had high rolling resistance, and Specialized later re-designed
the Touring II with a much wider and less tall center ridge. The
old T-II's did seem better than most of the tires available 15 yrs. ago,
but I suspect that they were even better after the ridge wore off.
Mick.
Somebody wrote:
> >> Any idea why that might be? Any data anywhere? Seems hard to believe.
> >> The footprint will be almost the same at the same pressure and loading
> >> for the K and non-K tires.
Jobst wrote:
> >From your question it seems that you believe that rolling resistance
> >is a function of contact patch size and its scrubbing on the road.
> >This is what was behind the raised center ridge Specialized Touring II
> >tires that had minimal road contact but high rolling resistance
In article <haubert.64...@mbi.org>,hau...@mbi.org wrote:
> Oops. Jobst, the formula for contact area is X / Y, where X = load on the
> tire, and Y = air pressure in tire. Pretty simple, and it doesn't vary
> depending on the tire!
>
> As I recall, the main purpose of the center ridge was to extend tire life,
> which it did. At the time they were tested as having LOWER than average
> rolling resistance.
-------------------==== Posted via Deja News ====-----------------------
hau...@mbi.org
In article <5sb8g4$m...@hplms2.hpl.hp.com> jbr...@hpl.hp.com (Jobst Brandt) writes:
>From: jbr...@hpl.hp.com (Jobst Brandt)
>Subject: Re: do kelvar belts stop flats?
>Date: 7 Aug 1997 01:30:44 GMT
>>> From your question it seems that you believe that rolling resistance
>>> is a function of contact patch size and its scrubbing on the road.
>>> This is what was behind the raised center ridge Specialized Touring II
>>> tires that had minimal road contact but high rolling resistance
>> Oops. Jobst, the formula for contact area is X / Y, where X = load
>> on the tire, and Y = air pressure in tire. Pretty simple, and it
>> doesn't vary depending on the tire!
>Oh? You mean if I ride on a steel grating that has 50% transmission, the
>contact patch of my tire will double?
Again Jobst must resort to absurd examples to try to detract attention from
the fact that he misspoke. Why don't you just admit when you're wrong, Jobst?
I never said that you weren't USUALLY right.
I must assume you never rode a
>raised center ridge tire or you would have noticed that it left behind a
>tire mark no wider than the ridge of about 6mm. Since the same tire worn
>smooth left a track of more than twice that, something in your analysis
>doesn't add up.
Wrong again. I rode touring II's for quite a few years. It took pretty high
pressure, and a pretty new ridge for your statement to be true. Of course
that still doesn't change the laws of physics. The contact area was simply
longer.
>Your formula may be simple, but it does not represent reality, nor does
>it apply to any tire except a tire with a 100% pliable casing that has
>not tread pattern on it. Knobby tires come to mind in this respect.
Knobby tires have 'not' tread pattern?? Now you're getting bizarre!
I agree that casing pliability makes a difference, but most high performance,
non-belted road tires have a similar pliability. Comparing ATB tires to road
racing tires is of no relevance.
>> As I recall, the main purpose of the center ridge was to extend tire
>> life, which it did. At the time they were tested as having LOWER
>> than average rolling resistance.
>I don;t know from where you "recall" that, besides that that concept
>is untrue. Stop making this stuff up as you go.
Now you're really grasping at straws. I could just as easily claim your
opinions are made up, but I don't. And, I readily admit that my memories
are just that, as opposed to your assertions that all of your opinions are
'verified facts'.
>>> Kevlar and especially Mr Tuffys are like molasses for the tire and
>>> make it absorb ore energy when it deforms.
>> I agree with Jobst here, although 30% definitely sounds high. Given
>> no definitive empirical evidence to the contrary, though, I'll take
>> his word for it, so long as it's legitimate testing data, not just a
>> figure off the top of his head.
>In contrast to your "recollections", this was from tests of tires with
>100% Kevlar belts.
Perhaps you'd best look up 'recollection'. Your representations of tests
are no more legitimate than mine. Even if you read it yesterday, it's still
a recollection, and, it's no more than your interpretation of the test.
This result was so high that the belts used by
>Avocet are a composite that is intended to optimize puncture protection
>and rolling resistance. I don;t believe it does either of those well.
Wow, a bad word about avocet from Jobst? Must not get a piece of the belted
ones.
Rich
Jobst Brandt
Rich Haubert writes:
>>>> These tires have at least 30% more rolling resistance than the
>>>> same tire without the Kevlar.
>>> Any idea why that might be? Any data anywhere? Seems hard to believe.
>>> The footprint will be almost the same at the same pressure and loading
>>> for the K and non-K tires.
>> From your question it seems that you believe that rolling resistance
>> is a function of contact patch size and its scrubbing on the road.
>> This is what was behind the raised center ridge Specialized Touring II
>> tires that had minimal road contact but high rolling resistance
> Oops. Jobst, the formula for contact area is X / Y, where X = load
> on the tire, and Y = air pressure in tire. Pretty simple, and it
> doesn't vary depending on the tire!
Oh? You mean if I ride on a steel grating that has 50% transmission,
the contact patch of my tire will double? I must assume you never
rode a raised center ridge tire or you would have noticed that it left
behind a tire mark, no wider than the thread ridge of about 6mm.
Since the same tire worn smooth left a track of more than twice that,
something in your analysis doesn't add up.
Your formula may be simple, but it does not represent reality, nor
does it apply to any tire except one with a 100% pliable casing with
no tread pattern in contrast to knobby tires for instance.
> As I recall, the main purpose of the center ridge was to extend tire
> life, which it did. At the time they were tested as having LOWER
> than average rolling resistance.
I don't know from where you "recall" that, besides that it isn't true.
Stop making this stuff up as you go.
>> Kevlar and especially Mr Tuffys are like molasses for the tire and
>> make it absorb ore energy when it deforms.
> I agree with Jobst here, although 30% definitely sounds high. Given
> no definitive empirical evidence to the contrary, though, I'll take
> his word for it, so long as it's legitimate testing data, not just a
> figure off the top of his head.
In contrast to your "recollections", this was from tests of tires with
100% Kevlar belts. This result was so high that the belts used by
Avocet are a composite that is intended to optimize puncture protection
and rolling resistance. I don't believe it does either of those well.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
Rich Haubert writes:
>>>> From your question it seems that you believe that rolling resistance
>>>> is a function of contact patch size and its scrubbing on the road.
>>>> This is what was behind the raised center ridge Specialized Touring II
>>>> tires that had minimal road contact but high rolling resistance
>>> Oops. Jobst, the formula for contact area is X / Y, where X = load
>>> on the tire, and Y = air pressure in tire. Pretty simple, and it
>>> doesn't vary depending on the tire!
>> Oh? You mean if I ride on a steel grating that has 50%
>> transmission, the contact patch of my tire will double?
> Again Jobst must resort to absurd examples to try to detract
> attention from the fact that he misspoke. Why don't you just admit
> when you're wrong, Jobst? I never said that you weren't USUALLY
> right.
Don't be so oblique. The contact area of tread on the ground is not
only governed by tire pressure and load but rather the geometry of the
contact. Just imagine driving a car on railroad tracks as "road
railers", the maintenance vehicles of railroads, do. Their contact
patch on the rail is substantially smaller than on the road. This is
the inverse of the raised center ridge tire.
Reviewing how a tire supports a load and how it keeps the rim off the
ground, the air pressure itself does not do that because pressure is
uniform around the wheel with no net lift. Inflation pressure
stretches the tire casing that pulls radially on the rim at a uniform
lateral angle. It is this angle that changes when the tire presses
against the road and causes a reduction in the downward component of
the casing tension. That is, locally in the bulge at the ground, the
casing pulls more to the side than the rest of the tire. Also,
tension is reduced because it is inversely related to cross section
curvature.
Hence, the only requirement for a tire to support a load is that its
casing bulges enough to reduce downward pull by an amount equal to the
load. This can be accomplished while resting on a relative knife edge
with a contact area substantially smaller than your proposed "formula
for contact".
>> I must assume you never rode a raised center ridge tire or you
>> would have noticed that it left behind a tire mark no wider than
>> the ridge of about 6mm. Since the same tire worn smooth left a
>> track of more than twice that, something in your analysis doesn't
>> add up.
> Wrong again. I rode Touring II's for quite a few years. It took
> pretty high pressure, and a pretty new ridge for your statement to
> be true. Of course that still doesn't change the laws of physics.
> The contact area was simply longer.
Well I'll admit that I don't know whether you rode these tires but I
am not wrong about your not noticing the relationship between their
contact area and tread shape. It definitely was not twice as long nor
could you see any difference in the height of the tire off the road.
Normal recommended inflation allowed the tire to ride with only the
ridge on the road and it did this until the ridge lost about half its
height. If you read the advertisements of the day, you would recall
that they claimed the smaller contact patch reduced rolling losses.
I don't understand where you are trying go with your argument other
than to find that I make all this stuff up the way you do. Just look
it up in old magazines. Low RR was the pitch for the raised center
ridge.
>> Your formula may be simple, but it does not represent reality, nor
>> does it apply to any tire except a tire with a 100% pliable casing
>> that has no tread pattern on it. Knobby tires come to mind in this
>> respect.
> I agree that casing pliability makes a difference, but most high
> performance, non-belted road tires have a similar pliability.
> Comparing ATB tires to road racing tires is of no relevance.
The point is relevant because it shows that raised tread patterns can
reduce road contact and that your formula applies only to smooth
highly flexible casings. The Touring II tire has all its "knobs"
lined up down its center.
>>> As I recall, the main purpose of the center ridge was to extend
>>> tire life, which it did. At the time they were tested as having
>>> LOWER than average rolling resistance.
And how did it plan to do that? With a smaller contact patch, wear
was concentrated on the narrow and highly stressed ridge that wore off
more rapidly than the remainder of the tire, once the ridge was gone.
I rode most of those tires into the cords and more than half the
mileage of the tire came after the ridge was gone. The ridge was
about 2/3 of the tread thickness.
>> I don't know from where you "recall" that, besides that that
>> concept is untrue. Stop making this stuff up as you go.
> Now you're really grasping at straws. I could just as easily claim
> your opinions are made up, but I don't. And, I readily admit that
> my memories are just that, as opposed to your assertions that all of
> your opinions are 'verified facts'.
I don't think you can make that claim. You may not notice that I
present easily verifiable reasons or ones you can recognize as true in
contrast to your postulations of, for instance, that a tread ridge
should last longer than smooth tread. I think it is established that
bumps wear off faster than large flat areas, even in absolute volume.
>>>> Kevlar and especially Mr Tuffys are like molasses for the tire
>>>> and make it absorb ore energy when it deforms.
>>> I agree with Jobst here, although 30% definitely sounds high.
>>> Given no definitive empirical evidence to the contrary, though,
>>> I'll take his word for it, so long as it's legitimate testing
>>> data, not just a figure off the top of his head.
>> In contrast to your "recollections", this was from tests of tires
>> with 100% Kevlar belts.
> Perhaps you'd best look up 'recollection'. Your representations of
> tests are no more legitimate than mine. Even if you read it
> yesterday, it's still a recollection, and, it's no more than your
> interpretation of the test.
I was involved in the development of Avocet smooth tread tires as well
as their response to the demand for Kevlar belted tires. In that
pursuit, IRC, the manufacturer of these tires furnished performance
data on various material compositions for the belts. I have seen this
information and reported on it, you have not. Your "recollection" is
more like a guess and has no basis on having ever seen measurement data.
>> This result was so high that the belts used by Avocet are a
>> composite that is intended to optimize puncture protection and
>> rolling resistance. I don't believe it does either of those well.
> Wow, a bad word about Avocet from Jobst? Must not get a piece of
> the belted ones.
Make that a bad word about Kevlar and the Kevlar/titanium/Teflon crowd.
After all, that is the subject under which this appears.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
Mick Tradermic(?) writes:
>> Sealants have another hazard that the makers of the stuff are
>> apparently not aware. A slimy substance inside the tube will make
>> a bicycle uncontrollable in the event the tire goes flat from a
>> cut, something sealant will not block.
> I'm not sure I can agree with Jobst on this one. IMHO, bikes with
> suddenly deflated tires have no lateral control at the wheel with
> the flat tire, sealant or no sealant. The severity seems related to
> the speed you're going more than anything else.
I think you lost the context. My point was that even on a straight
level road, where a flat on a conventional road tire on the rear wheel
is benign, goo in the tube causes an effect almost as though the rear
end were on ice. As others have mentioned, they as I, haver ridden
many miles on a flat tire with no control problems, when this was the
only option. The point is that a rear flat becomes a more dangerous
situation if the inside of the tube is lubricated with a sealant.
Jobst Brandt <jbr...@hpl.hp.com>
Geoffrey Levand
jbr...@hpl.hp.com (Jobst Brandt):
>> I agree with Jobst here, although 30% definitely sounds high. Given
>> no definitive empirical evidence to the contrary, though, I'll take
>> his word for it, so long as it's legitimate testing data, not just a
>> figure off the top of his head.
>
>In contrast to your "recollections", this was from tests of tires with
>100% Kevlar belts. This result was so high that the belts used by
>Avocet are a composite that is intended to optimize puncture protection
>and rolling resistance. I don;t believe it does either of those well.
But how does tire rolling resistance compare with air resistance while
cycling. I mean, if we're only talking about a small fraction of
total drag -- who cares.
G. Levand
hau...@mbi.org
In article <5sfli7$8...@hplms2.hpl.hp.com> jbr...@hpl.hp.com (Jobst Brandt) writes:
>From: jbr...@hpl.hp.com (Jobst Brandt)
>Subject: Re: do kelvar belts stop flats?
>Don't be so oblique. The contact area of tread on the ground is not
>only governed by tire pressure and load but rather the geometry of the
>contact. Just imagine driving a car on railroad tracks as "road
>railers", the maintenance vehicles of railroads, do. Their contact
>patch on the rail is substantially smaller than on the road. This is
>the inverse of the raised center ridge tire.
This example is similar, albeit less interesting and less verifiable, than
Mick's: car tires are very thick - designed to make a very wide contact patch
at varying pressures. The tires we are supposed to be speaking of are high
pressure, smooth bike tires. I appreciate the try, though.
>Reviewing how a tire supports a load and how it keeps the rim off the
>ground, the air pressure itself does not do that because pressure is
>uniform around the wheel with no net lift. Inflation pressure
>stretches the tire casing that pulls radially on the rim at a uniform
>lateral angle. It is this angle that changes when the tire presses
>against the road and causes a reduction in the downward component of
>the casing tension. That is, locally in the bulge at the ground, the
>casing pulls more to the side than the rest of the tire. Also,
>tension is reduced because it is inversely related to cross section
>curvature.
Excellent explanation, Jobst! I agree. But, I still maintain that with
smooth roads and smooth skinwalls, the difference is insignificant.
>> I rode Touring II's for quite a few years. It took
>> pretty high pressure, and a pretty new ridge for your statement to
>> be true. Of course that still doesn't change the laws of physics.
>> The contact area was simply longer.
>Well I'll admit that I don't know whether you rode these tires
Ah, so now you simply don't believe me! Perhaps now you can start to
understand why people don't always believe you? The difference is, I and most
people try to give others the benefit of the doubt. This is something I have
never seen you do.
>Normal recommended inflation allowed the tire to ride with only the
>ridge on the road and it did this until the ridge lost about half its
>height. If you read the advertisements of the day, you would recall
>that they claimed the smaller contact patch reduced rolling losses.
Didn't I say that same thing a couple posts ago??
>I don't understand where you are trying go with your argument other
>than to find that I make all this stuff up the way you do.
That is EXACTLY the problem. Every time someone disagrees with you, you
always assume they made it up.
>> I agree that casing pliability makes a difference, but most high
>> performance, non-belted road tires have a similar pliability.
>> Comparing ATB tires to road racing tires is of no relevance.
>The point is relevant because it shows that raised tread patterns can
>reduce road contact and that your formula applies only to smooth
>highly flexible casings.
And that's exactly what I said it did! So now you AGREE with me?
>And how did it plan to do that? With a smaller contact patch, wear
>was concentrated on the narrow and highly stressed ridge that wore off
>more rapidly than the remainder of the tire, once the ridge was gone.
>I rode most of those tires into the cords and more than half the
>mileage of the tire came after the ridge was gone. The ridge was
>about 2/3 of the tread thickness.
Yes! - the only tires I consistently wore into the cords. I wonder why that
is?
This brings up an interesting point that I've been wondering about. You'll
probably accuse me of changing the subject, and probably I am, but, extending
tread life is obviously a very old idea. Manufacturers must always try to
strike a balance between tread life, traction, cut resistance, rolling
resistance, and weight. Now, as we will hopefully agree on, thickening the
tread and/or casing increases weight and rolling resistance. To increase
tread life, then, one need only increase the rubber that touches the road,
provided of course that the casing is already of satisfactory durability.
Since this is essentially the same as using a raised ridge (touring II), how
is tread life increased without increasing rolling resistance?
It'd be interesting to know your opinion based on your tire experience.
>contrast to your postulations of, for instance, that a tread ridge
>should last longer than smooth tread. I think it is established that
>bumps wear off faster than large flat areas, even in absolute volume.
Not at all. I said that a smooth tread combined with the ridge should last
longer than the smooth tread without the ridge. Are you disputing that?
>> Perhaps you'd best look up 'recollection'. Your representations of
>> tests are no more legitimate than mine. Even if you read it
>> yesterday, it's still a recollection, and, it's no more than your
>> interpretation of the test.
>I was involved in the development of Avocet smooth tread tires as well
>as their response to the demand for Kevlar belted tires. In that
>pursuit, IRC, the manufacturer of these tires furnished performance
>data on various material compositions for the belts. I have seen this
>information and reported on it, you have not.
Now wait a minute! Data on kevlar belts? Despite the subject header, this is
clearly not what you and I have been discussing. I already said I agree with
you that belts increase rolling resistance, anyway.
Your "recollection" is
>more like a guess and has no basis on having ever seen measurement data.
As I said before, my 'recollection' was from what I read some fourteen years
ago. Yours is apparently more recent, but is still a recollection,
nevertheless.
>Make that a bad word about Kevlar and the Kevlar/titanium/Teflon crowd.
Well, that's good to know, I guess.
Rich
trad...@rocketmail.com
> Jobst Brandt <jbr...@hpl.hp.com> wrote:
> My point was that even on a straight
> level road, where a flat on a conventional road tire on the rear wheel
> is benign, goo in the tube causes an effect almost as though the rear
> end were on ice. As others have mentioned, they as I, haver ridden
> many miles on a flat tire with no control problems, when this was the
> only option. The point is that a rear flat becomes a more dangerous
> situation if the inside of the tube is lubricated with a sealant.
And the reason for this is that with a dry tube, traction is
transmitted from the tread to the tube to the sidewall to
the rim? And if the tube is internally lubricated this chain
of events breaks down? Makes sense to me now.
Thanx, JB. Glad I don't use sealants anyway.
Mick.
Jobst Brandt
Rich Haubert writes:
>> Don't be so oblique. The contact area of tread on the ground is
>> not only governed by tire pressure and load but rather the geometry
>> of the contact. Just imagine driving a car on railroad tracks as
>> "road railers", the maintenance vehicles of railroads, do. Their
>> contact patch on the rail is substantially smaller than on the
>> road. This is the inverse of the raised center ridge tire.
> This example is similar, albeit less interesting and less
> verifiable, than Mick's: car tires are very thick - designed to make
> a very wide contact patch at varying pressures. The tires we are
> supposed to be speaking of are high pressure, smooth bike tires. I
> appreciate the try, though.
So you believe that the rigidity of the tire tread makes this
possible? The rigidity of the car tire on the RR rail is
insignificant to the load carried and would collapse around the rail
were it not for the cord tension effects that support the rim, as I
described. The same is true for a 700-28 bicycle tire support
lengthwise on a 1/8 wide steel bar.
>> Reviewing how a tire supports a load and how it keeps the rim off the
>> ground, the air pressure itself does not do that because pressure is
>> uniform around the wheel with no net lift. Inflation pressure
>> stretches the tire casing that pulls radially on the rim at a uniform
>> lateral angle. It is this angle that changes when the tire presses
>> against the road and causes a reduction in the downward component of
>> the casing tension. That is, locally in the bulge at the ground, the
>> casing pulls more to the side than the rest of the tire. Also,
>> tension is reduced because it is inversely related to cross section
>> curvature.
> Excellent explanation, Jobst! I agree. But, I still maintain that
> with smooth roads and smooth skinwalls, the difference is
> insignificant.
What difference? If you place your bike with tires normally inflated
on a 1/4 inch wide flat ridge, it will not deflect perceptibly more
than normal (although there is a slight increase) and only a narrow
contact patch, marginally longer than normal will occur. That is what
the raised center ridge did and it was claimed that the reduced
contact also reduced rolling resistance.
>>> I rode Touring II's for quite a few years. It took pretty high
>>> pressure, and a pretty new ridge for your statement to be true.
>>> Of course that still doesn't change the laws of physics. The
>>> contact area was simply longer.
Since the normal contact patch is more than 1/2 inch wide, is seems
the length of the raised ridge's contact would be nearly twice as long
and would thereby ride like a flat tire, that is hard to steer because
it's contact patch is so long. This is not the case.
>> Well I'll admit that I don't know whether you rode these tires
Hold it. Where's the rest of this sentence and to what was it referring.
> Ah, so now you simply don't believe me! Perhaps now you can start
> to understand why people don't always believe you? The difference
> is, I and most people try to give others the benefit of the doubt.
> This is something I have never seen you do.
You don't read carefully. I do that whenever writers make claims with
no supporting evidence or logical explanation, such as your assertion
that tire contact area is the load divided by inflation pressure.
That is not correct and you gave no reason why anyone should believe
that. I think you can see a different approach in my explanation of
how a tire supports a rim. That is not such an unsupported statement.
>> Normal recommended inflation allowed the tire to ride with only the
>> ridge on the road and it did this until the ridge lost about half its
>> height. If you read the advertisements of the day, you would recall
>> that they claimed the smaller contact patch reduced rolling losses.
> Didn't I say that same thing a couple posts ago??
The above statement is what started this and you disagreed with it.
It seems we have a moving target. What is your contention and how does
it differ from my position.
>> I don't understand where you are trying go with your argument other
>> than to find that I make all this stuff up the way you do.
> That is EXACTLY the problem. Every time someone disagrees with you, you
> always assume they made it up.
Well, if it isn't true and you state it emphatically with no attribution,
what else is one to deduce than you made it up. Tom and Ray Magliozzi
called it the MAS syndrome (male answer syndrome) and described it in
detail. "In the absence of the right answer, make one up. Who's going
to challenge it?"
>>> I agree that casing pliability makes a difference, but most high
>>> performance, non-belted road tires have a similar pliability.
>>> Comparing ATB tires to road racing tires is of no relevance.
>> The point is relevant because it shows that raised tread patterns can
>> reduce road contact and that your formula applies only to smooth
>> highly flexible casings.
> And that's exactly what I said it did! So now you AGREE with me?
I see. If you pull this out long enough you will try to switch our
positions on the subject entirely. You ARE making this up.
>> And how did it plan to do that? With a smaller contact patch, wear
>> was concentrated on the narrow and highly stressed ridge that wore off
>> more rapidly than the remainder of the tire, once the ridge was gone.
>> I rode most of those tires into the cords and more than half the
>> mileage of the tire came after the ridge was gone. The ridge was
>> about 2/3 of the tread thickness.
> Yes! - the only tires I consistently wore into the cords. I wonder
> why that is?
Why are you asking me. I just told you why and that your logic of that
the raise center ridge extended wear life doesn't make sense, since the ridge
accelerated wear.
> This brings up an interesting point that I've been wondering about.
> You'll probably accuse me of changing the subject, and probably I
> am, but, extending tread life is obviously a very old idea.
> Manufacturers must always try to strike a balance between tread
> life, traction, cut resistance, rolling resistance, and weight.
> Now, as we will hopefully agree on, thickening the tread and/or
> casing increases weight and rolling resistance. To increase tread
> life, then, one need only increase the rubber that touches the road,
> provided of course that the casing is already of satisfactory
> durability. Since this is essentially the same as using a raised
> ridge (touring II), how is tread life increased without increasing
> rolling resistance?
Tread life has been more than doubled since the rubber compounds of
the Touring II tire that required me to rotate tires on my Alpine
tours in the summer. Today I ride Avocet Road 28's, pump them up
before I leave for Europe, and don't touch them for two months as I
ride farther than I did altogether on those old tires.
Smooth tread reduced rolling resistance as does thinner tread. The
Avocet smooth tires have no more tread thickness than Touring II had
but have a 30% lower rolling resistance because the casings are
thinner and the tread is a different rubber that enhanced wear
resistance while not losing traction.
I mention Avocet because I am involved in their tire development and
know what was measured. Many other tire brands use the same improved
rubber today, but because there are many traditionalists, patterned
tread is still found on many tires. It has no advantage on the road
and only increases rolling resistance.
>> contrast to your postulations of, for instance, that a tread ridge
>> should last longer than smooth tread. I think it is established that
>> bumps wear off faster than large flat areas, even in absolute volume.
> Not at all. I said that a smooth tread combined with the ridge should last
> longer than the smooth tread without the ridge. Are you disputing that?
I beg your pardon, you said the raised center ridge was not to reduce
rolling resistance but to increase wear life, when I pointed out that
RR comes from elastomeric hysteresis, not from the size of the contact
patch.
>>> Perhaps you'd best look up 'recollection'. Your representations of
>>> tests are no more legitimate than mine. Even if you read it
>>> yesterday, it's still a recollection, and, it's no more than your
>>> interpretation of the test.
>> I was involved in the development of Avocet smooth tread tires as well
>> as their response to the demand for Kevlar belted tires. In that
>> pursuit, IRC, the manufacturer of these tires furnished performance
>> data on various material compositions for the belts. I have seen this
>> information and reported on it, you have not.
> Now wait a minute! Data on Kevlar belts? Despite the subject
> header, this is clearly not what you and I have been discussing. I
> already said I agree with you that belts increase rolling
> resistance, anyway.
You forgot how we got here. You may have jumped in when I mentioned the
rolling losses of Kevlar belted tires and that RR was much higher.
>> Your "recollection" is more like a guess and has no basis on having
>> ever seen measurement data.
> As I said before, my 'recollection' was from what I read some
> fourteen years ago. Yours is apparently more recent, but is still a
> recollection, nevertheless.
You state things authoritatively as though you were current on the
subject and now you back out with "14 years ago [in a magazine]".
OK. I give up.
Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
Geoffrey Levand writes:
> But how does tire rolling resistance compare with air resistance
> while cycling. I mean, if we're only talking about a small fraction
> of total drag -- who cares.
It's small but significant anyway, because the human is such a weak
engine. RR is relatively constant over a wide range of speeds, so the
slower (weaker) you are the greater it affects you. In contrast, the
faster you are the more important the 1/10's of seconds become.
Jobst Brandt <jbr...@hpl.hp.com>
Thomas H. Kunich
In article <33ea5058...@nnrp.gol.com>,
Geoffrey Levand <gle...@gol.com.NoSpamPlease> wrote:
>But how does tire rolling resistance compare with air resistance while
>cycling. I mean, if we're only talking about a small fraction of
>total drag -- who cares.
Shhh! No one is suppose to remember that part.
Yes, rolling resistance really isn't too important in the big picture.
Following my reading of Jobst's data about fat tires having better
overall performance than thin tires, I changed to 25 and 28 mm Avocets
and here is what I found:
I rode 3,500 miles on a rear tire! The best I ever got with any other
tire was 3,000 miles on a Continental Cran Prix and I had to rotate
the tires and ride on them with BIG flat centers to get that much.
The Avocet didn't get ONE puncture flat but that might be luck.
On the other hand I have 28's on my Colnago and I haven't had a puncuture
on those either (knock on wood). It isn't as if tires are bulletproof
though. Yesterday a guy I was riding with picked up a dry-wall screw
that went through the tire, tube AND RIM.
THe Avocets typically ride better than any other tire I've tried except
Michelin SuperComp HD's which never wore more than 1,500 miles for me.
Avocets have good traction wet or dry.
Avocets seem to mount no harder than other tires after the first
mounting, though that first one is a bear. Yet The SuperComps were
worse.
So, even though I've given Jobst a hard time in the past, I have to
admit that he is spot on when he talks about the Avocet FastGrip 20's.
They are available, I believe, from Nashbar. Don't know why they aren't
at Performance.
Wayne Pein
Thomas H. Kunich wrote:
>
> So, even though I've given Jobst a hard time in the past, I have to
> admit that he is spot on when he talks about the Avocet FastGrip 20's.
>
> They are available, I believe, from Nashbar. Don't know why they aren't
> at Performance.
In the current Nashbar catalog, these are only available in
27in size. For 700s, they come with a Kevlar belt unfortunately.
If anyone knows of a good source for 700 x 28,32,35 Avocet Fasgrip 20
let me know. My LBS that can order them isn't really local.
Wayne
TBGibb
In article <5sj9an$k...@hplms2.hpl.hp.com>, jbr...@hpl.hp.com (Jobst
Brandt) writes:
> Many other tire brands use the same improved
>rubber today, but because there are many traditionalists, patterned
>tread is still found on many tires. It has no advantage on the road
>and only increases rolling resistance.
When you speak of "patterned tread" are you refering to a tire like the
Vredestein Fortezza (which appears to have a texture pressed into the
rubber) or something like the Continental Grand Prix 3000 (or both)?
Tom Gibb <TBG...@aol.com>
Jobst Brandt
Tom Gibb writes:
> When you speak of "patterned tread" are you referring to a tire like the
> Vredestein Fortezza (which appears to have a texture pressed into the
> rubber) or something like the Continental Grand Prix 3000 (or both)?
Patterned tread in contrast to smooth tread (or slicks). As usual, the
bicycle community has redefined tread to mean tread pattern. The tread
is the rubber that meets the ground. It can be smooth of be patterned,
ribbed, knobby, or otherwise.
Jobst Brandt <jbr...@hpl.hp.com>