Tire puzzle

Frankie left us with a formidable conundrum.

When you make a choice of equipment to obtain improvement, it is likely that
its effects are negligible and that the negative effects associated with it
will outweigh and overcome any minuscule advantage predicted.

So ..............

If you mount a narrow tire to achieve a better aerodynamic factor, that
factor is negligible and will in fact bring with it a slowing factor due to
[one of many] increased rolling resistance.

Take another look from the other side -

If you mount a wide tire to achieve a decreased rolling resistance, that
factor is negligible and will in fact bring with it a slowing factor due to
[one of many] a poorer aerodynamic factor.

So I am paralyzed. At least I put on new tires and can't afford to spend on
replacements to test out any theory. Maybe by the time they wear out,
Frankie will have returned to explain it all. The tires, should anyone
care, are the Force & Attack pair that I picked up for 20€ together. I do
have my preferences, but I fear to note them here.
--
Bonne route !

Sandy
Verneuil-sur-Seine

"Sandy" wrote: (clip) If you mount a narrow tire to achieve a better
aerodynamic factor, that
factor is negligible and will in fact bring with it a slowing factor due
to [one of many] increased rolling resistance. (clip)
^^^^^^^^^^^^^^^^^^
Your information is incorrect. A wider tire will have *increased* rolling
resistance. That makes this the easiest puzzle I ever worked on.

On Tue, 10 Mar 2009 10:25:43 -0700, Leo Lichtman wrote:

"Sandy" wrote: (clip) If you mount a narrow tire to achieve a better
aerodynamic factor, that
factor is negligible and will in fact bring with it a slowing factor
due to [one of many] increased rolling resistance. (clip)
^^^^^^^^^^^^^^^^^^
Your information is incorrect. A wider tire will have *increased*
rolling resistance. That makes this the easiest puzzle I ever worked
on.

haha. Agreed. As Sheldon points out, narrow tyres have higher rolling
resistance when at the same pressure as a wider one but such a tyre would
be grossly under inflated (or the wider one massive over) and unsuitable
for riding.

Leo Lichtman wrote:
Your information is incorrect. *A wider tire will have *increased* rolling
resistance. *


Is that true? I always thought that everything else being equal
(including pressure), a wider tire would have less rolling resistance.

Art Harris

On Tue, 10 Mar 2009 11:30:58 -0700, Art Harris wrote:

Leo Lichtman wrote:
Your information is incorrect. Â*A wider tire will have *increased*
rolling resistance.


Is that true? I always thought that everything else being equal
(including pressure), a wider tire would have less rolling resistance.

Art Harris

It will but at an appropriate pressure, not an equal one (I think??)

From Sheldons page:

"...A common debate among cyclists centers on the issue of whether a wider
tire has more or less rolling resistance at the same pressure. The
constant pressure is proposed because it appears more scientific to
eliminate this as a variable, but this is not realistic in practice. The
short answer to this question is that, yes, a wider tire of similar
construction will have lower rolling resistance than a narrower one at the
same pressure. This fact is, however, of no practical value. If you are
comparing two tires of similar construction, with the same load, and the
same pressure, either the wider tire is overinflated, or the narrower tire
is underinflated!..."

On Tue, 10 Mar 2009 19:27:55 +0000, Keiron wrote:

On Tue, 10 Mar 2009 11:30:58 -0700, Art Harris wrote:

Leo Lichtman wrote:
Your information is incorrect. Â*A wider tire will have *increased*
rolling resistance.


Is that true? I always thought that everything else being equal
(including pressure), a wider tire would have less rolling resistance.

Art Harris

It will but at an appropriate pressure, not an equal one (I think??)

Scratch that and reverse it. At it's recommended (higher) pressure a
narrow tyre will have less rolling resistance than a wider tyre at its
recommended (lower) pressure.

Keiron wrote:

Is that true? I always thought that everything else being equal
(including pressure), a wider tire would have less rolling resistance.
Art Harris

It will but at an appropriate pressure, not an equal one (I think??)

Scratch that and reverse it. At it's recommended (higher) pressure a
narrow tyre will have less rolling resistance than a wider tyre at its
recommended (lower) pressure.


Sheldon's article doesn't exactly say that. He says that it's not fair
to compare wide and narrow tires at the same pressure. But he says
that if you did, the wider tire would have lower RR.

http://sheldonbrown.com/tires.html#rolling

That still leaves the possibility that a slightly wider tire at a
slightly lower pressure might have the same RR as a narrower one at
higher pressure. Or maybe even a bit lower. And this all assumes
similar construction (casing, tread, etc.).


Art Harris

Keiron wrote:

Leo Lichtman wrote:

"Sandy" wrote: *
(clip)
If you mount a narrow tire to achieve a better
aerodynamic factor, that
factor is negligible and will in fact bring with it a slowing factor
due to [one of many] increased rolling resistance. (clip)
^^^^^^^^^^^^^^^^^^
Your information is incorrect. *A wider tire will have *increased*
rolling resistance. *That makes this the easiest puzzle I ever worked
on.

haha. Agreed. As Sheldon points out, narrow tyres have higher rolling
resistance when at the same pressure as a wider one but such a tyre would
be grossly under inflated (or the wider one massive over) and unsuitable
for riding.

Solar racer tires, which have similar per-tire loadings and for which
minimum rolling resistance and aerodynamic profile are the highest
priorities, are quite a bit wider than racing bike tires. Do you
think Michelin, GM, and MIT are mistaken about this?

Wider bike tires with lower pressure often go faster on less than
totally smooth surfaces, because they do not use up as much of the
bike's kinetic energy into jarring the rider (who is a highly damped
system). Otherwise track racers and road racers and cyclocrossers and
MTB racers could all succeed with the same sort of tires.

Chalo

On Tue, 10 Mar 2009 13:03:27 -0700, Chalo wrote:

Keiron wrote:

Leo Lichtman wrote:

"Sandy" wrote:
(clip)
If you mount a narrow tire to achieve a better aerodynamic factor,
that
factor is negligible and will in fact bring with it a slowing factor
due to [one of many] increased rolling resistance. (clip)
^^^^^^^^^^^^^^^^^^
Your information is incorrect. Â*A wider tire will have *increased*
rolling resistance. Â*That makes this the easiest puzzle I ever worked
on.

haha. Agreed. As Sheldon points out, narrow tyres have higher rolling
resistance when at the same pressure as a wider one but such a tyre
would be grossly under inflated (or the wider one massive over) and
unsuitable for riding.

Solar racer tires, which have similar per-tire loadings and for which
minimum rolling resistance and aerodynamic profile are the highest
priorities, are quite a bit wider than racing bike tires. Do you think
Michelin, GM, and MIT are mistaken about this?

Alas I know not about solar racer tyres and can neither dispute those
company's claims but I don't know that you can compare these like for
like. I don't know that solar racer and bicycle tyres are meant to perform
in any similar manner. Do they cover the same type of surfaces, how wide
are they? What are they made from?


Wider bike tires with lower pressure often go faster on less than
totally smooth surfaces, because they do not use up as much of the
bike's kinetic energy into jarring the rider (who is a highly damped
system). Otherwise track racers and road racers and cyclocrossers and
MTB racers could all succeed with the same sort of tires.

Chalo

I don't dispute what you say but I don't feel that this is a like for like
comparison.

I'm definitely no engineer, was just reiterating what I saw as commonly
accepted.

Cheers

On Tue, 10 Mar 2009 12:55:56 -0700, Art Harris wrote:

Keiron wrote:

Is that true? I always thought that everything else being equal
(including pressure), a wider tire would have less rolling
resistance. Art Harris

It will but at an appropriate pressure, not an equal one (I think??)

Scratch that and reverse it. At it's recommended (higher) pressure a
narrow tyre will have less rolling resistance than a wider tyre at its
recommended (lower) pressure.


Sheldon's article doesn't exactly say that. He says that it's not fair
to compare wide and narrow tires at the same pressure. But he says that
if you did, the wider tire would have lower RR.

http://sheldonbrown.com/tires.html#rolling

That still leaves the possibility that a slightly wider tire at a
slightly lower pressure might have the same RR as a narrower one at
higher pressure. Or maybe even a bit lower. And this all assumes similar
construction (casing, tread, etc.).


Art Harris

Yep, can't argue with that logic but what Sheldon then says, as i see it,
a wider tyre at a lower than recommended pressure (or any tyre at a
pressure for which it's not ideally suited) likely wouldn't perform in the
way it was intended. Again that's not to say that there's not a wide
(enough) tyre at a low enough pressure that doesn't have a lesser rolling
resistance by design that narrow tyres. I'd just imagine the instances of
that are less?

To be fair i hold my hands up and admit i'm just guessing.


Cheers