Radiall stiffness

Quoted post said:

Originally posted by George
Hi, Did you watch on TV the last Tour of Flandres? That's
my question. Some wise people say that high profile rim
wheel radiall stiffness is the same as in low profile rim
ones. If they really have right, why on Tour of Flandres or
Paris-Roubaix riders use only low profile rim wheels?
Regards, George

Didn't see the Race, but I think the radail stiffness issue is something Jobst Brandt would be quite qualified to answer.
I doubt that you could feel the difference in radial stiffness of the rim itself due to large radial tire elasticity.
When I build wheels I can tell that I get about 1 mm less radial rim shrinkage on a CXP-33 rim than a OpenPro with the same amount of spoke tension. However, when you ride the tensioned wheel, I don't think the radial stifness difference would be significant.

George said:

Hi, Did you watch on TV the last Tour of Flandres?

Episode of the Simpsons?

Bill "ride around the Bible Belt w/Ned" S.

S o r n i said:

Episode of the Simpsons?

On what newsgroup did you write? alt.tv.simpsons?
Regards, George.

George said:

S o r n i said:

Episode of the Simpsons?

On what newsgroup did you write? alt.tv.simpsons?

Ya see, Ned Flanders is...oh, never mind.

Bill "besides, you snipped all reference material" S.

George said:

Some wise people say that high profile rim wheel radiall
stiffness is the same as in low profile rim ones. If they
really have right, why on Tour of Flandres or Paris-
Roubaix riders use only low profile rim wheels?

One possibility is that racers are a suggestible folk, quick
to adopt things that they believe to be to their advantage,
but loath to discard those things which previous race
winners have in common. There is a ton of folklore
surrounding races held on cobblestone courses, much of which
may have been valid at some historical time.

Another possibility is that such race routes as you mention
lend themselves well to the use of fatter-than-normal tires
at lower-than-normal pressures. Tires at low pressure behave
more predictably when mounted on rims close to the width of
the tire. The wider types of lightweight racing rims will
tend to have a low profile. Whether racers in the events you
named actually use wider than usual rims, I don't know.

I don't believe I've heard anybody suggest that the radial
stiffness of wheels with high and low profile rims is identical--
what they have pointed out is that there is not a
perceptible amount of "give" in the rim of a properly
tensioned wheel before the spokes in the affected area go
completely slack, and that if they do this more than
occasionally, the wheel will fail in a very short time.
Therefore wheels that last for many miles demonstrate that
they have not been absorbing any detectable amount of shock.

Chalo Colina

George said:

Hi, Did you watch on TV the last Tour of Flandres? That's
my question. Some wise people say that high profile rim
wheel radiall stiffness is the same as in low profile rim
ones. If they really have right, why on Tour of Flandres
or Paris-Roubaix riders use only low profile rim wheels?

Probably because they prefer to use "conventional" wheels
for durability on cobbled surfaces, as opposed to the ultra
light aerodynamic wheels that are fairly commonly used in
pro racing now. I guess you could ask why they don't use 32
spoke wheels with a strong aero rim like a Deep V - perhaps
a belief that they're too heavy (probably misguided).

"George" <[email hidden]> wrote in message
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Quoted message said:

Hi, Did you watch on TV the last Tour of Flandres? That's
my question. Some wise people say that high profile rim
wheel radiall stiffness is the same as in low profile rim
ones. If they really have right, why on Tour of Flandres
or Paris-Roubaix riders use only low profile rim wheels?
Regards, George

Because they absorb more and lessen the shock.

Imagine racing on cobblestone streets. Imagine your fillings
rattling loose.

Dave

onefred said:

George said:

why on Tour of Flandres or Paris-Roubaix riders use only
low profile rim wheels?

Because they absorb more and lessen the shock.

Absolutely. After rattling away on rims with a mere 0.01" of
deflection, the whopping 0.02" deflection of low profile
rims are like riding on a cloud.

(Numbers completely made up to make a point.)
--
terry morse Palo Alto, CA bike.terrymorse.combike.terrymorse.comOpen ↗

"Terry Morse" <[email hidden]> wrote in message
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Quoted message said:

onefred said:

George said:

why on Tour of Flandres or Paris-Roubaix riders use
only low profile rim wheels?

Because they absorb more and lessen the shock.

Absolutely. After rattling away on rims with a mere 0.01"
of deflection, the whopping 0.02" deflection of low
profile rims are like riding on a cloud.

(Numbers completely made up to make a point.)

Wow, a 50% difference. Didn't think it'd be so great.
Perhaps I should consider building a set of aero wheels for
myself. Actually, I've been planning this for the past few
months. Already got the hubs and spokes... Woohoo!

Dave