aero rims stronger?
Brian Plaugher
trued for 3 years since purchase. I have the idea that the wheels are
stronger because the rims are aero. Some site on the net opined that
the v-shaped part of aero wheels is less significant in durability
than beefiness at the rim edge. What do folks here say: aero wheels
stronger? If so, by how much?
Brian Plaugher
jobst....@stanfordalumni.org
Why do you want a stronger rim? Stronger is a pretty vague term but
it sells all sorts of products. If you mean radial bending stiffness,
then yes, but how much is useful? In fact deep cross section rims are
essential to low spoke count wheels, there being such a large span
between spokes. So at the cost of a heavier wheel, the spoke count
can be reduced. I don't know how your previous rims wore out but it
was most likely not from this feature.
People who ride much over anything but ideal road surfaces, a dinged
rim bead is a common failure and for others who descend mountain roads
in rain, side walls wearing out is common. This does not seem to be
the focus on wheels but rather wheels with unusual spoke patterns,
colored rims and odd shaped spokes seems more important than
durability these days, which floods the market with these products
along with colored tires and other gimmicks.
Jobst Brandt <jobst....@stanfordalumni.org> Palo Alto CA
Alex Rodriguez
eucon...@msn.com says...
Wheel strenght depends on spoke tightness. Generally speaking a V shaped
rim will allow a higher spoke tension than a box shaped rim. Of course
the builder has to know this and build the wheel with the higher tension
the rim allows.
-----------------
Alex __O
_-\<,_
(_)/ (_)
Amit
> Brian Plaugher writes:
>
> > I have some CXP-30 rims that are rock solid, have not needed to be
> > trued for 3 years since purchase. I have the idea that the wheels
> > are stronger because the rims are aero. Some site on the net opined
> > that the v-shaped part of aero wheels is less significant in
> > durability than beefiness at the rim edge. What do folks here say:
> > aero wheels stronger? If so, by how much?
>
> Why do you want a stronger rim? Stronger is a pretty vague term but
> it sells all sorts of products. If you mean radial bending stiffness,
> then yes, but how much is useful? In fact deep cross section rims are
> essential to low spoke count wheels, there being such a large span
> between spokes. So at the cost of a heavier wheel, the spoke count
> can be reduced. I don't know how your previous rims wore out but it
> was most likely not from this feature.
>
The question is not about low spoke count wheels. Are you just
bringing that up so you can rant about it ? The CXP-30 is a V-shaped
550 gram rim which was available in most common drillings (28, 32, 36
holes).
> People who ride much over anything but ideal road surfaces, a dinged
> rim bead is a common failure and for others who descend mountain roads
> in rain, side walls wearing out is common.
> This does not seem to be
> the focus on wheels but rather wheels with unusual spoke patterns,
> colored rims and odd shaped spokes seems more important than
> durability these days, which floods the market with these products
> along with colored tires and other gimmicks.
>
We've heard this same tired tirade many times. What's the relevance
here ?
-Amit Ghosh
tb
> Brian Plaugher writes:
>
> > I have some CXP-30 rims that are rock solid, have not needed to be
> > trued for 3 years since purchase. I have the idea that the wheels
> > are stronger because the rims are aero. Some site on the net opined
> > that the v-shaped part of aero wheels is less significant in
> > durability than beefiness at the rim edge. What do folks here say:
> > aero wheels stronger? If so, by how much?
>
> Why do you want a stronger rim?
>
how about stronger meaning that cracks dont develope around the spoke
eyelets after 16 months of riding, or is that to much to ask for?
Abram Dancy
> SNIP
> People who ride much over anything but ideal road surfaces, a dinged
> rim bead is a common failure and for others who descend mountain roads
> in rain, side walls wearing out is common. This does not seem to be
What does a worn out side wall look like? How do you judge how much wear is
too much? Any particular reason that they'd wear out faster in the rain?
Certainly pads wear faster wet, but rims? Or is it just that you've got to
use the brakes more in the rain, descending at a slower speed, and thus
having less wind resistance?
Curiously,
Abram Dancy
jobst....@stanfordalumni.org
>>> I have some CXP-30 rims that are rock solid, have not needed to be
>>> trued for 3 years since purchase. I have the idea that the wheels
>>> are stronger because the rims are aero. Some site on the net opined
>>> that the v-shaped part of aero wheels is less significant in
>>> durability than beefiness at the rim edge. What do folks here say:
>>> aero wheels stronger? If so, by how much?
>> Why do you want a stronger rim? Stronger is a pretty vague term but
>> it sells all sorts of products. If you mean radial bending stiffness,
>> then yes, but how much is useful? In fact deep cross section rims are
>> essential to low spoke count wheels, there being such a large span
>> between spokes. So at the cost of a heavier wheel, the spoke count
>> can be reduced. I don't know how your previous rims wore out but it
>> was most likely not from this feature.
> The question is not about low spoke count wheels. Are you just
> bringing that up so you can rant about it ? The CXP-30 is a V-shaped
> 550 gram rim which was available in most common drillings (28, 32, 36
> holes).
That gets back to the first question, how "strong" is useful and for
what? A deep aero cross section makes the rim heavier and the aero
advantage comes to play in the 0.01 seconds in a flat TT. The
promotions for such rims seldom if ever show what percent of rider
effort is reduced by using aero rims, small cross section tires and
pumping them to unusually high tires. It turns out that these are
insignificant differences easily below tucking in your shirt or
keeping the zipper on the jersey all the way up.
>> People who ride much over anything but ideal road surfaces, a
>> dinged rim bead is a common failure and for others who descend
>> mountain roads in rain, side walls wearing out is common.
>> This does not seem to be the focus on wheels but rather wheels with
>> unusual spoke patterns, colored rims and odd shaped spokes seems
>> more important than durability these days, which floods the market
>> with these products along with colored tires and other gimmicks.
> We've heard this same tired tirade many times. What's the relevance
> here ?
You don't need no steenkin aero rims. That's what. They only lighten
your wallet.
jobst....@stanfordalumni.org
>>> I have some CXP-30 rims that are rock solid, have not needed to be
>>> trued for 3 years since purchase. I have the idea that the wheels
>>> are stronger because the rims are aero. Some site on the net
>>> opined that the v-shaped part of aero wheels is less significant
>>> in durability than beefiness at the rim edge. What do folks here
>>> say: aero wheels stronger? If so, by how much?
>> Why do you want a stronger rim?
> How about stronger meaning that cracks dont develope around the
> spoke eyelets after 16 months of riding, or is that to much to ask
> for?
Don't buy anodized rims.
jobst....@stanfordalumni.org
>> People who ride much over anything but ideal road surfaces, a
>> dinged rim bead is a common failure and for others who descend
>> mountain roads in rain, side walls wearing out is common. This
>> does not seem to be SNIP
> What does a worn out side wall look like? How do you judge how much
> wear is too much? Any particular reason that they'd wear out faster
> in the rain? Certainly pads wear faster wet, but rims?
Rain water on roads moves fine grit slurry, especially in rocky areas,
onto the braking surfaces and wears rims at a rate most riders would
never expect. Of course MTB riders should be used to that in the mud
and wet.
> Or is it just that you've got to use the brakes more in the rain,
> descending at a slower speed, and thus having less wind resistance?
You were doing just fine until you offered this addendum.
Bicycle rim wear is almost exclusively caused by road grit. Ridden in
dry weather, rims last eons. We often hear testimonials here how
someone's antique bicycle, ridden only in fair weather, still has
equipment and brakes that haven't been around in 20 years.
Kraig Willett
The UCI has an interesting perspective on this topic. They deem
any wheel that has a rim depth greater than 25 mm "questionable"
in terms of safety - and wheels built with these rims must be
subject to a poorly conceived "rupture" (impact) test.
The specifics of this test aside, (if you want, you can read all
about it at),
in my experience with catastrophically testing bicycle wheels,
(I have destroyed hundreds under laboratory conditions)
the CXP-30 is among the strongest rims out there. The
weakest rims when considering catastrophic failure due to radial
impacts, as would be expected, are the shallow tubular rims
such as the Ambrosio Crono, Mavic GL 280, Mavic GEL 330.
To Jobst's point, however, the real question is: how strong is
strong enough? In my opinion, when dealing with catastrophic
failures, the GL 280 is not strong enough - and it fails at
approximately 600-800 in-lb of energy when built up with
32 spokes and struck with a blunt faced pendulum. The
CXP-30 with 28 spokes would not even flinch at this
energy level.
--
==========================
Kraig Willett
K-dub Enterprises
Technical Writing
Product Evaluation
Market Surveys
==========================
Kraig Willett
> Amit Ghosh writes:
>
> >>> I have some CXP-30 rims that are rock solid, have not needed to be
> >>> trued for 3 years since purchase. I have the idea that the wheels
> >>> are stronger because the rims are aero. Some site on the net opined
> >>> that the v-shaped part of aero wheels is less significant in
> >>> durability than beefiness at the rim edge. What do folks here say:
> >>> aero wheels stronger? If so, by how much?
>
> >> Why do you want a stronger rim? Stronger is a pretty vague term but
> >> it sells all sorts of products. If you mean radial bending stiffness,
> >> then yes, but how much is useful? In fact deep cross section rims are
> >> essential to low spoke count wheels, there being such a large span
> >> between spokes. So at the cost of a heavier wheel, the spoke count
> >> can be reduced. I don't know how your previous rims wore out but it
> >> was most likely not from this feature.
>
> > The question is not about low spoke count wheels. Are you just
> > bringing that up so you can rant about it ? The CXP-30 is a V-shaped
> > 550 gram rim which was available in most common drillings (28, 32, 36
> > holes).
>
> That gets back to the first question, how "strong" is useful and for
> what? A deep aero cross section makes the rim heavier and the aero
> advantage comes to play in the 0.01 seconds in a flat TT.
Not according to the results from wind tunnel tests I have witnessed.
Furthermore, the analysis that I did for bike.com last year:
disagrees with this statement. Are you sure that you aren't
exaggerating just to make a point?
>The
> promotions for such rims seldom if ever show what percent of rider
> effort is reduced by using aero rims, small cross section tires and
> pumping them to unusually high tires. It turns out that these are
> insignificant differences easily below tucking in your shirt or
> keeping the zipper on the jersey all the way up.
Insignificant is a poor word choice.
Kraig Willett
In my experience with durability testing modern day bicycle wheels
in a laboratory environment (and extensive personal road use), I
have found there to be little to worry about when using cosmetic
anodized rims.
There is a much better correlation between
rim wall thickness (both in the brake track and in the spoke
bed) and fatigue failure than anodize/non anodize
surface treatments.
I have also seen many failures due to improperly installed
double-walled eyelets/spoke sockets.
In the battle of generalities: "don't buy badly designed rims".
Brian Plaugher
>
> Why do you want a stronger rim?
What I want is a durable wheel. My CXP-30s have 36 spokes, not the
fewer number or non-standard spokes seen these days. I am building up
a second bike, and have the option of getting some CXP33s (32 spoke).
My sole interest in aero rims is for overall wheel durability. My
question, rephrased: to what extent do aero rims add to the durability
of a wheel?
Brian Plaugher
Kraig Willett
> From: <jobst....@stanfordalumni.org>
> > SNIP
> > People who ride much over anything but ideal road surfaces, a dinged
> > rim bead is a common failure and for others who descend mountain roads
> > in rain, side walls wearing out is common. This does not seem to be
> > SNIP
>
> What does a worn out side wall look like? How do you judge how much wear is
> too much?
Since Jobst didn't answer your question, I'll tell you what I have noticed:
1) the brake track becomes noticeably dished/concave
(you can feel it with your finger - if you don't know by touch, odds
are you are OK)
2) the lab tests I have conducted indicate that failure is imminent (will
happen in the short term, not if, but when the rim will fail) when the
brake track is on the order of .8 to .9mm (.032 - .036 in) thick.
Most rims have brake tracks that are 1.3 to 1.5 mm thick.
Amit
As Jobst said rims do wear out too. The braking surface is worn thin.
I've had the bead fold over when the rim was worn. I've heard that the
sidewall can crack but I haven't experienced this.
This is one reason I don't like the fact rims serve double duty as
braking surfaces. Evantually you'll have to retire a favorite wheelset
if you use it a lot.
-Amit Ghosh
Amit
> Amit Ghosh writes:
>
> That gets back to the first question, how "strong" is useful and for
> what? A deep aero cross section makes the rim heavier and the aero
> advantage comes to play in the 0.01 seconds in a flat TT. The
> promotions for such rims seldom if ever show what percent of rider
> effort is reduced by using aero rims, small cross section tires and
> pumping them to unusually high tires. It turns out that these are
> insignificant differences easily below tucking in your shirt or
> keeping the zipper on the jersey all the way up.
>
Or keeping your mouth closed ? yuk yuk yuk. Seriously though, if one
wants a 550 g rim because it can be made into a strong wheel, why not
?
> >> This does not seem to be the focus on wheels but rather wheels with
> >> unusual spoke patterns, colored rims and odd shaped spokes seems
> >> more important than durability these days, which floods the market
> >> with these products along with colored tires and other gimmicks.
>
> > We've heard this same tired tirade many times. What's the relevance
> > here ?
>
> You don't need no steenkin aero rims. That's what. They only lighten
> your wallet.
>
I bought two blue tires for $12, Canadian dollars no less!
-Amit Ghosh
Qui si parla Campagnolo
trued for 3 years since purchase. I have the idea that the wheels are
stronger because the rims are aero. >>
V shape makes them strong but their weight also does..tese are pretty beefy
rims-
Peter Chisholm
Vecchio's Bicicletteria
1833 Pearl ST.
Boulder, CO, 80302
(303)440-3535
http://www.vecchios.com
Tom H
> To Jobst's point, however, the real question is: how strong is
> strong enough? In my opinion, when dealing with catastrophic
> failures, the GL 280 is not strong enough - and it fails at
> approximately 600-800 in-lb of energy when built up with
> 32 spokes and struck with a blunt faced pendulum. The
> CXP-30 with 28 spokes would not even flinch at this
> energy level.
When I took up riding again a few years ago, I went through six sets
of wheels in the first year(I was quite heavy at the time)until I
happened upon some Campy Eurus 20s. I've still got these wheels and
have done no maintenance to them except service the hubs. They have 20
spokes and a rim similar in dimensions to the CXP30. Since then I've
used CXP30's (32 spokes)(and one pair of CXP14s - maybe even better)
and find they build up to robust trouble free wheels. I've never
broken a spoke on an "aero" rimmed wheel, whereas I used to carry
spares when I rode my old MA2s. The CXP30 may be a bit of overkill for
a light rider unless you go for a low spoke count. It's a shame they
are now so hard to find for us heavier guys!
Tom
Paul Kopit
stronger, tighter wheels?
I'm thinking specifically of a Mavic CXP33 with no offset vs a
Velocity Aerohead where the spokes are offset. In my actual
esperience, it seems like ~100 kgF/drive side is close to the tension
limit. I'll even assume that the ERD, 598 is the same, knowing that
some of th Aeroheads are 602.
I don't want to cloud the issue with ferrules.
Paul Kopit
time. I have a decent micrometer. On rims that have been used for an
estimated 10,000 miles or 'used' rims, I can measure difference
between front and rear rims. BUT, as I said, you need a measuring
device that is accurate to 1/1000.
On Tue, 23 Apr 2002 02:32:40 GMT, jobst....@stanfordalumni.org
wrote:
jobst....@stanfordalumni.org
None. If the tire bottoms on a road hazard it will generally dent the
bead of the rim, which is no stronger on a deep sectioned rim than on
others. Sidewall wear is also the same, sidewalls being much the same
across the field of rims, although machined rims may be slightly
thinner locally. As far as load carrying, the old socket and eyelet
Mavic MA-2 was, in my estimation, the best all around rim. I don't
have loose spokes and the rims remain true through many 1000 miles,
usually failing from worn out sidewalls, but also from dings in the
bead. I have a collection of these in my garage.
jobst....@stanfordalumni.org
>> What does a worn out side wall look like? How do you judge how
>> much wear is too much?
> 1) the brake track becomes noticeably dished/concave (you can feel
> it with your finger - if you don't know by touch, odds are you
> are OK)
> 2) the lab tests I have conducted indicate that failure is imminent
> (will happen in the short term, not if, but when the rim will
> fail) when the brake track is on the order of .8 to .9mm (.032 -
> .036 in) thick. Most rims have brake tracks that are 1.3 to 1.5
> mm thick.
That is a bit more generous that what my experience gives. I think
0.5mm is the limit but 0.9mm is a bit soon to trash a rim. I have
examples of 0.5mm worn out rims that served well to the last without
generating cracks. Of course, these were MA-2 rims.
As you say, the hollow cheeks are th measure. If nothing else, lay a
straight edge across the sidewall and see how it compares with the new
rim.
Tom Nakashima
These are the only rims I ride on. Great braking surface, strong, stays
true, I've only trued my 36 sp, MA-2 rims twice in two years. I ride
everyday.
My only wish is that Mavic still made these rims. I still haven't found a
replacement.
-tom
<jobst....@stanfordalumni.org> wrote in message
news:7Xgx8.19860$44.1...@typhoon.sonic.net...
Bluto
> Wheel strenght depends on spoke tightness. Generally speaking a V shaped
> rim will allow a higher spoke tension than a box shaped rim.
This is contrary to observations I have made during wheelbuilding.
Generally speaking, I have noted that for a given spoke count and rim
diameter, it is rim weight and not cross-sectional shape that dictates
the maximum spoke tension I can apply before the rim goes squiggly.
Spoke tension does not apply a radial bending load to the rim. Spokes
apply a circumferential compressive load (with a much smaller lateral
bending component). It appears to me that the column strength of a
rim is proportional to the material cross-section, rather than the
area enclosed by the cross-section.
I have assumed that tall sections were employed for their span
rigidity or aerodynamic benefit, rather than because they were capable
of supporting higher spoke tensions than wider, shallower sections.
Perhaps Jobst Brandt could address this issue.
Do aero section rims support higher spoke tensions than box section
rims of equivalent weight? This seems to be a common impression, but
I have not observed it to be the case in practice.
Chalo Colina
Kraig Willett
> Kraig Willett <kwil...@adelphia.net.remove> writes:
>
> >> What does a worn out side wall look like? How do you judge how
> >> much wear is too much?
>
> > 1) the brake track becomes noticeably dished/concave (you can feel
> > it with your finger - if you don't know by touch, odds are you
> > are OK)
>
> > 2) the lab tests I have conducted indicate that failure is imminent
> > (will happen in the short term, not if, but when the rim will
> > fail) when the brake track is on the order of .8 to .9mm (.032 -
> > .036 in) thick. Most rims have brake tracks that are 1.3 to 1.5
> > mm thick.
>
> That is a bit more generous that what my experience gives. I think
> 0.5mm is the limit but 0.9mm is a bit soon to trash a rim. I have
> examples of 0.5mm worn out rims that served well to the last without
> generating cracks. Of course, these were MA-2 rims.
I reckon your body weight was more important to these wheels surviving
"to the last" with .5 mm brake tracks than the fact that they were
MA-2's.
My lab experience is based on an ~160 lb radial load.
And, I never thought it possible that I would give a more
conservative recommendation than Jobst Brandt - by a mere
0.012 - 0.016 in!! : )
In all seriousness, _I_ wouldn't press my luck with 0.020 in (.5mm)
of brake track.
jobst....@stanfordalumni.org
>>>> What does a worn out side wall look like? How do you judge how
>>>> much wear is too much?
>>> 1) the brake track becomes noticeably dished/concave (you can feel
>>> it with your finger - if you don't know by touch, odds are you
>>> are OK)
>>> 2) the lab tests I have conducted indicate that failure is
>>> imminent (will happen in the short term, not if, but when the
>>> rim will fail) when the brake track is on the order of .8 to
>>> .9mm (.032 - .036 in) thick. Most rims have brake tracks that
>>> are 1.3 to 1.5 mm thick.
>> That is a bit more generous that what my experience gives. I think
>> 0.5mm is the limit but 0.9mm is a bit soon to trash a rim. I have
>> examples of 0.5mm worn out rims that served well to the last
>> without generating cracks. Of course, these were MA-2 rims.
> I reckon your body weight was more important to these wheels
> surviving "to the last" with .5 mm brake tracks than the fact that
> they were MA-2's.
> My lab experience is based on an ~160 lb radial load.
My road experience is with 200+ lbs, the load that the front wheel
sees under hard braking with rider, bicycle and saddlebag resting on
the front wheel only.
> And, I never thought it possible that I would give a more
> conservative recommendation than Jobst Brandt - by a mere 0.012 -
> 0.016 in!!
Of 1.5mm wall that's 27%, not so small as I see it.
> In all seriousness, _I_ wouldn't press my luck with 0.020 in (.5mm)
> of brake track.
THe wqay you say that, it sounds as thought you sell rims. By the
way, my steel frame is getting soft.
Kraig Willett
> Kraig Willett writes:
> >> That is a bit more generous that what my experience gives. I think
> >> 0.5mm is the limit but 0.9mm is a bit soon to trash a rim. I have
> >> examples of 0.5mm worn out rims that served well to the last
> >> without generating cracks. Of course, these were MA-2 rims.
>
> > I reckon your body weight was more important to these wheels
> > surviving "to the last" with .5 mm brake tracks than the fact that
> > they were MA-2's.
>
> > My lab experience is based on an ~160 lb radial load.
>
> My road experience is with 200+ lbs, the load that the front wheel
> sees under hard braking with rider, bicycle and saddlebag resting on
> the front wheel only.
For how many cycles? What air pressure? What tire size?
I don't know what we are discussing now. I was under the
impression we were discussing fatigue.
I have tested at a _constant_ load of 100kg, with worse results
than at 75 kg. In fact, the .9mm walls failed on the order of a
thousand kilometers.
Be my guest at field testing with .5 mm walls.
I would recommend changing rims wth brake tracks in the
.8-.9mm range. No sense in getting out in the middle of no
where and having your sidewall fold out to try and save
50 bucks.
> > And, I never thought it possible that I would give a more
> > conservative recommendation than Jobst Brandt - by a mere 0.012 -
> > 0.016 in!!
>
> Of 1.5mm wall that's 27%, not so small as I see it.
Actually, its 20-27%. I specified a range.
No sense of humor, like always.
> > In all seriousness, _I_ wouldn't press my luck with 0.020 in (.5mm)
> > of brake track.
>
> THe wqay you say that, it sounds as thought you sell rims. By the
> way, my steel frame is getting soft.
Why must you assume anything about me?
I have designed a few rims in the past, but don't sell them.
By the way, the cosmetic anodizing is making my aero rims
fail while they save me .01s in a flat time trial.
Aaron Fillion
<jobst....@stanfordalumni.org> wrote in message
news:7Xgx8.19860$44.1...@typhoon.sonic.net...
> Brian Plaugher writes:
>
> >> Why do you want a stronger rim?
>
> > What I want is a durable wheel. My CXP-30s have 36 spokes, not the
> > fewer number or non-standard spokes seen these days. I am building
> > up a second bike, and have the option of getting some CXP33s (32
> > spoke). My sole interest in aero rims is for overall wheel
> > durability. My question, rephrased: to what extent do aero rims add
> > to the durability of a wheel?
>
> None. If the tire bottoms on a road hazard it will generally dent the
> bead of the rim, which is no stronger on a deep sectioned rim than on
> others.
I have on a few occasions nailed small potholes very hard with my road wheels
and the deep sectioned rims have never dented. With the MA2's I have hit a
pothole with a similar amount of force and the rim did crush inwards. I do not
think it is just the bead. When I looked at the sidewall as it passed by the
brakepads, the sidewall at its inner most part passes by the brake pads at a
lower level, which suggests to me the entire rim had been crushed inward.
tubus import en framebouw
>
> Kraig Willett <kwil...@adelphia.net.remove> writes:
>
> >> What does a worn out side wall look like? How do you judge how
> >> much wear is too much?
>
> > 1) the brake track becomes noticeably dished/concave (you can feel
> > it with your finger - if you don't know by touch, odds are you
> > are OK)
>
> > 2) the lab tests I have conducted indicate that failure is imminent
> > (will happen in the short term, not if, but when the rim will
> > fail) when the brake track is on the order of .8 to .9mm (.032 -
> > .036 in) thick. Most rims have brake tracks that are 1.3 to 1.5
> > mm thick.
>
> That is a bit more generous that what my experience gives. I think
> 0.5mm is the limit but 0.9mm is a bit soon to trash a rim. I have
> examples of 0.5mm worn out rims that served well to the last without
> generating cracks. Of course, these were MA-2 rims.
>
I pulled a few samples out of the trash of rims cracked in service. They
all failed at about 0.9mm. Highly unscientific, but all a very long way
of 0.5mm
--
Marten
jobst....@stanfordalumni.org
You didn't say whether the bead was mashed down, although it seems
that you don't exclude this. So? Who cares whether the rim is
destroyed AND has a flat spot in it. When the bead is bent down you
have a shot rim. I find it odd that this issue gets attacked from
whichever side is convenient. The expensive rim is better because it
makes me go faster (in the flat), it is better because it is harder to
crush, I use 18mm tires because mass at the periphery of the wheel is
most important, and so on.
These are oh so thin excuses for spending money instead of riding
bike. Meanwhile, the question is brought to wreck.bike to get
attention that doesn't give the RIGHT answers. Do it but don't expect
to ask whether it's worth the trouble.
jobst....@stanfordalumni.org
>> Kraig Willett <kwil...@adelphia.net.remove> writes:
>>>> What does a worn out side wall look like? How do you judge how
>>>> much wear is too much?
>>> 1) the brake track becomes noticeably dished/concave (you can feel
>>> it with your finger - if you don't know by touch, odds are you
>>> are OK).
>>> 2) the lab tests I have conducted indicate that failure is
>>> imminent (will happen in the short term, not if, but when the
>>> rim will fail) when the brake track is on the order of .8 to
>>> .9mm (.032 - .036 in) thick. Most rims have brake tracks that
>>> are 1.3 to 1.5 mm thick.
>> That is a bit more generous that what my experience gives. I think
>> 0.5mm is the limit but 0.9mm is a bit soon to trash a rim. I have
>> examples of 0.5mm worn out rims that served well to the last
>> without generating cracks. Of course, these were MA-2 rims.
> I pulled a few samples out of the trash of rims cracked in
> service. They all failed at about 0.9mm. Highly unscientific, but
> all a very long way of 0.5mm
I'm curious. Were these anodized rims? I have not had a rim separate
and have worn them to 0.5mm as have others with whom I ride.
Kraig Willett
>I find it odd that this issue gets attacked from
> whichever side is convenient. The expensive rim is better because it
> makes me go faster (in the flat), it is better because it is harder to
> crush, I use 18mm tires because mass at the periphery of the wheel is
> most important, and so on.
Is your universe really this contorted?
I use aero rims when the application warrants.
I use narrow tires when the application warrants.
> These are oh so thin excuses for spending money instead of riding
> bike.
I reckon in the last ten years, I have ridden my bike more than you.
> Meanwhile, the question is brought to wreck.bike to get
> attention that doesn't give the RIGHT answers.
I don't follow this statement. Am I to assume that you are the
only one that gives RIGHT answers?
>Do it but don't expect
> to ask whether it's worth the trouble.
Who are you to judge the perception of "worth"
that another individual has? The best anyone can hope
for is to present the information and then let the individual
decide. This is the driving force behind my style of
product evaluation. I don't have the presumption, or
arrogance if you want my honest opinion, to impose my
values on someone else.
The way I see it, there are three fundamental design variables:
price, performance, and durability. What I value does not
necessarily reflect what the entire universe values- thank
goodness.
By the way, why didn't you address the valid
questions I posed about your "field test results"?
Aaron Fillion
<jobst....@stanfordalumni.org> wrote in message
news:lNGx8.22407$44.1...@typhoon.sonic.net...
> Aaron Fillion writes:
>
> >>>> Why do you want a stronger rim?
>
> >>> What I want is a durable wheel. My CXP-30s have 36 spokes, not
> >>> the fewer number or non-standard spokes seen these days. I am
> >>> building up a second bike, and have the option of getting some
> >>> CXP33s (32 spoke). My sole interest in aero rims is for overall
> >>> wheel durability. My question, rephrased: to what extent do aero
> >>> rims add to the durability of a wheel?
>
> >> None. If the tire bottoms on a road hazard it will generally dent
> >> the bead of the rim, which is no stronger on a deep sectioned rim
> >> than on others.
>
> > I have on a few occasions nailed small potholes very hard with my
> > road wheels and the deep sectioned rims have never dented. With the
> > MA2's I have hit a pothole with a similar amount of force and the
> > rim did crush inwards. I do not think it is just the bead. When I
> > looked at the sidewall as it passed by the brakepads, the sidewall
> > at its inner most part passes by the brake pads at a lower level,
> > which suggests to me the entire rim had been crushed inward.
>
> You didn't say whether the bead was mashed down, although it seems
> that you don't exclude this.
The bead had no noticable dent, it looked as though the entire section was
pushed in.
> So?
I guess my point was that in my experience deeper sectioned rims resist getting
crushed inwards.
In the case where the just the bead gets dented, the rim can still be ridable,
as is the case with my current front wheel. When the entire rim gets crushed
inward, the wheel has a hop that you can feel while riding, as was the case with
my old rear rim.
> Who cares whether the rim is
> destroyed AND has a flat spot in it. When the bead is bent down you
> have a shot rim. I find it odd that this issue gets attacked from
> whichever side is convenient. The expensive rim is better because it
> makes me go faster (in the flat), it is better because it is harder to
> crush, I use 18mm tires because mass at the periphery of the wheel is
> most important, and so on.
In the context of the discussion I was thinking of an aero rim as rims like
Mavic CXP-33, not a boutique wheel.
I don't think that the more expensive wheel is harder to crush, the rims that
are more durable always seem to be the ones that weigh more.
Bluto
> ...The expensive rim is better because it
> makes me go faster (in the flat), it is better because it is harder to
> crush, I use 18mm tires because mass at the periphery of the wheel is
> most important, and so on.
>
> These are oh so thin excuses for spending money instead of riding
> bike. Meanwhile, the question is brought to wreck.bike to get
> attention that doesn't give the RIGHT answers. Do it but don't expect
> to ask whether it's worth the trouble.
You didn't answer-- perhaps failed to notice-- elsewhere in the thread
where I asked you to weigh in on the question of whether a tall
section rim supports higher spoke tension than a box section rim of
equal weight. My impression from tensioning many wheels to the yield
point is that the rim's cross-sectional shape _does not_ seem to make
a difference; others say that a deep rim can take more spoke tension.
So which is it? Is it only the mass of the rim that dictates max
spoke tension, or does the extrusion shape also play a part? Because
if a tall or tall & wide section rim can support more spoke tension
than a rim of compact sectional proportions but equal mass, then there
is no question but that it could be built into a wheel of higher load
bearing capacity.
Chalo Colina
Kraig Willett
>My impression from tensioning many wheels to the yield
> point is that the rim's cross-sectional shape _does not_ seem to make
> a difference; others say that a deep rim can take more spoke tension.
>
> So which is it? Is it only the mass of the rim that dictates max
> spoke tension, or does the extrusion shape also play a part
In my experience of designing, analyzing, and testing rims,
I have found that box shaped rims are not as mass efficient as
ones that have a "v" type of shape and slightly thicker
spoke beds.
This disc brake rim (show in cross section about half
way down the page):
http://www.spinergy.com/xyclonedisctechsheet.htm
was what I came up with when trying to acheive an ~ 400g
design goal. I didn't get a chance to evaluate the design (i.e,
lab test it) before I moved on to another job. That
was two and a half years ago, and they are still
using it - so it can't be a _total_ disaster.
Bluto
> Bluto <chump...@hotmail.com> wrote:
> > So which is it? Is it only the mass of the rim that dictates max
> > spoke tension, or does the extrusion shape also play a part
>
> In my experience of designing, analyzing, and testing rims,
> I have found that box shaped rims are not as mass efficient as
> ones that have a "v" type of shape and slightly thicker
> spoke beds.
Most of my pertinent experience has been in building 48 spoke wheels
with 550g and heavier rims. This set of conditions allows me to
routinely and ordinarily bring the wheel to the point at which the rim
begins to collapse under compressive load. The spokes are often below
their optimal tension level when this occurs, so integrity of the
spoke bed is not an issue at all.
I believe that using an adequate spoke count for a given rim will by
definition allow this compressional collapse to occur before the spoke
bed is overstressed; if the reverse were the case, I would suggest
that the wheel had too few spokes to allow the rim to be built to its
potential.
With 48 spokes, the circumferential compressional strength of the rim
is always the weak link that determines maximum spoke tension.
Which is what led me to my original question: Does the extrusion
shape play a part in giving a rim its compressional strength, or is it
only the material cross-sectional area that does that?
Chalo Colina
R. Himm
jobst....@stanfordalumni.org wrote:
> Aaron Fillion writes:
> >> None. If the tire bottoms on a road hazard it will generally dent
> >> the bead of the rim, which is no stronger on a deep sectioned rim
> >> than on others.
>
> > I have on a few occasions nailed small potholes very hard with my
> > road wheels and the deep sectioned rims have never dented. With the
> > MA2's I have hit a pothole with a similar amount of force and the
> > rim did crush inwards. I do not think it is just the bead. When I
> > looked at the sidewall as it passed by the brakepads, the sidewall
> > at its inner most part passes by the brake pads at a lower level,
> > which suggests to me the entire rim had been crushed inward.
>
> You didn't say whether the bead was mashed down, although it seems
> that you don't exclude this. So? Who cares whether the rim is
> destroyed AND has a flat spot in it. When the bead is bent down you
Sometimes it does help to read the post. I don't see any way to interpret
this except that he says, with the deep sectioned rims, he has gotten
NEITHER the flat spot NOR the bead mashed down, for pothole slams big
enough to get BOTH with MA2s.
Kraig Willett
> "Kraig Willett" <kwil...@adelphia.net.remove> wrote:
>
> > Bluto <chump...@hotmail.com> wrote:
>
> > > So which is it? Is it only the mass of the rim that dictates max
> > > spoke tension, or does the extrusion shape also play a part
> >
> > In my experience of designing, analyzing, and testing rims,
> > I have found that box shaped rims are not as mass efficient as
> > ones that have a "v" type of shape and slightly thicker
> > spoke beds.
>
> Most of my pertinent experience has been in building 48 spoke wheels
> with 550g and heavier rims.
BMX?
>This set of conditions allows me to
> routinely and ordinarily bring the wheel to the point at which the rim
> begins to collapse under compressive load.
And where does the buckling occur? When I have seen rims
fail in compression, the buckling starts in the plane of the
least cross-sectional inertia - the spoke hole. Is this consistent
with your experience?
>The spokes are often below
> their optimal tension level when this occurs, so integrity of the
> spoke bed is not an issue at all.
> I believe that using an adequate spoke count for a given rim will by
> definition allow this compressional collapse to occur before the spoke
> bed is overstressed; if the reverse were the case, I would suggest
> that the wheel had too few spokes to allow the rim to be built to its
> potential.
> With 48 spokes, the circumferential compressional strength of the rim
> is always the weak link that determines maximum spoke tension.
Then I would suggest that your rims are poorly designed for a
48 spoke application.
> Which is what led me to my original question: Does the extrusion
> shape play a part in giving a rim its compressional strength, or is it
> only the material cross-sectional area that does that?
The formula for the critical load in an Euler column is:
Pcr = pi^2*E*I/L^2
with _I_ being cross sectional inertia which means that column
load carrying capacity is a function cross-sectional shape - this
is why the box shaped rim is the "easy" answer to the "what is the
best shape" question. My analysis at the time led me to a different
conclusion. Of course, the design goal was significanlty
different than anything that would require 48 spokes.
Amit
> To change the song slightly, do rims with offset spokes make for
> stronger, tighter wheels?
>
> I'm thinking specifically of a Mavic CXP33 with no offset vs a
> Velocity Aerohead where the spokes are offset. In my actual
> esperience, it seems like ~100 kgF/drive side is close to the tension
> limit. I'll even assume that the ERD, 598 is the same, knowing that
> some of th Aeroheads are 602.
>
spoke offset, but sometimes it's subtle.
Sheldon Brown mentions there are two ways of offseting the holes (left
hand and right hand, you guess which is which). Once while replacing a
rim I realized the replacment was drilled in the opposite handedness
as the original (same model). I wonder if the right handed rims are
for the British market ?
The Aerohead is a nice and inexpensive rim, but the spoke holes aren't
angled. I broke a spoke at the rim, first time I've done that and I
wonder if that was the cause.
-Amit Ghosh
A Muzi
news:df5bdaa0.02042...@posting.google.com...
-snip-
> Sheldon Brown mentions there are two ways of offseting the holes (left
> hand and right hand, you guess which is which). Once while replacing a
> rim I realized the replacment was drilled in the opposite handedness
> as the original (same model). I wonder if the right handed rims are
> for the British market ?
At one time, rims were drilled either on the Fiamme side (first to the right
of the valve is close to you) or on the Mavic side (first to the right of
the valve is away from you). Nowadays the convention is "Mavic" drill. It
makes absolutely no difference at all unless you are swapping a rim in a
built wheel.
--
Andrew Muzi, who finds Mavic drill "backwards" for some reason
http://www.yellowjersey.org
Open every day since 1 April 1971