Q. Will I benefit from different tire size or type?

On Sat, 2 Aug 2003 21:34:08 -0500, A Muzi wrote:
of pavement anomalies. Keep the pressure up always but especially if you
go to a skinnier tire.

In fact, the reason to go to a skinnier tire, afaik, is to
be able to use a higher pressure.

I recall a thread that discussed rolling resistance; and
some studies or experiments or something determined that
all things being equal (pressure, tread, compound, bike,
rider, temp, humidity, etc), a wider tire actually has
less rolling resistance. The real-world result, however,
was that narrower tires had lower rolling resistance due
to the higher pressures you could use.

Does anybody else remember that? I don't think it was on
these rec.bicycles newsfroups, but I can't imagine where
it WAS if that's the case.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
--
Rick Onanian

On Sun, 03 Aug 2003 17:50:48 GMT, OliverS
wrote:
However, knobbies take a bit toll on efficiency -- my guess based on my
personal performance experienc (somewhat subjective to be sure) about
25%.

The exception to that rule being knobbies with a centerline.
Such tires tend to be okay, and are often designed to turn
pretty well on pavement too.

Still, you're much better off with a slick or even a
semi-slick, and there's no reason whatsoever to use
a knobby unless you're doing moderate-to-heavy off-road
riding -- more than just dirt paths, grass, and unpaved
sections.

--
Rick Onanian

Does it not make sense that the fatter tire will have more rolling
resistance because the contact patch (and thus friction) will be greater
with the fatter tire? If you look at vehicles built for straight-line speed
(other than those where massive power needs to be transmitted to the
ground - definitely NOT bikes) be it soap-box racers to land speed record
assault rocket cars, the tires are hard and skinny to minimize rolling
resistance.

--

- GRL

"It's good to want things."

Steve Barr (philosopher, poet, humorist, chemist,
Visual Basic programmer)
"Rick Onanian" wrote in message
news
On Sat, 2 Aug 2003 21:34:08 -0500, A Muzi wrote:
of pavement anomalies. Keep the pressure up always but especially if you
go to a skinnier tire.

In fact, the reason to go to a skinnier tire, afaik, is to
be able to use a higher pressure.

I recall a thread that discussed rolling resistance; and
some studies or experiments or something determined that
all things being equal (pressure, tread, compound, bike,
rider, temp, humidity, etc), a wider tire actually has
less rolling resistance. The real-world result, however,
was that narrower tires had lower rolling resistance due
to the higher pressures you could use.

Does anybody else remember that? I don't think it was on
these rec.bicycles newsfroups, but I can't imagine where
it WAS if that's the case.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
--
Rick Onanian

"GRL" wrote in message
...
Does it not make sense that the fatter tire will have more rolling
resistance because the contact patch (and thus friction) will be greater
with the fatter tire?


Not necessarily. At a given tire pressure and weight, the contact patch is
*the same size*, no matter how wide (up to a point). Think PSI. Pounds per
sq inch.
A 200lb rider/bike creates a 2 sq in patch for a bike tire pumped to 100
psi. No matter what the width or diameter.

The contact patch will be a different shape for a wider vs skinnier tire.
Wide and short, instead of long and skinny. Less sidewall deformation as the
tire rolls.

This is, of course, making the huge assumption that all other factors are
equal (Tire construction, TPI , pressure, etc).

Width (wind resistance) may overcome the difference in Crr.

If you look at vehicles built for straight-line speed
(other than those where massive power needs to be transmitted to the
ground - definitely NOT bikes) be it soap-box racers to land speed record
assault rocket cars, the tires are hard and skinny to minimize rolling
resistance.

They are also skinny to minimise frontal area/wind resistance. Those types
of vehicles also do not have to worry about wear, traction in varying
conditions, marketing costs, etc.

Several tire rr tests have been done in the recumbent community.
http://www.beezodogsplace.com/Pages/...Resistance.pdf
http://www.legslarry.beerdrinkers.co.uk/tech/GS.htm

Pete

On Thu, 7 Aug 2003 20:08:29 -0400, GRL wrote:

Does it not make sense that the fatter tire will have more rolling
resistance because the contact patch (and thus friction) will be greater
with the fatter tire?

I thought this too, but I now believe that I was incorrect.

See http://www.sheldonbrown.com/tires.html#width

If you look at vehicles built for straight-line speed
(other than those where massive power needs to be transmitted to the
ground - definitely NOT bikes) be it soap-box racers to land speed record
assault rocket cars, the tires are hard and skinny to minimize rolling
resistance.

The narrow tires are more aerodynamic and can take higher pressures.

--
Rick Onanian

"Rick Onanian" wrote in message
news
On Fri, 08 Aug 2003 01:08:40 GMT, Pete wrote:
A 200lb rider/bike creates a 2 sq in patch for a bike tire pumped to 100
psi. No matter what the width or diameter.

Close. Actually, this would be correct:
A 200lb rider/unicycle creates a 2 sq in patch for a unicycle
tire pumped to 100 psi. No matter what the width or diameter.

Forgot that some of the rider's weight is on the _other_
bicycle tire?


ok, ok

But the concept still stands.

Pete