Why bicycle tyres are different from car tires

Simon Brooke sent three separate statements
each requiring explanation:

1. Contrary to common opinion, for any given rubber compound, (on
bicycles) slick tyres are better in the wet than tyres with tread.

2. They also tend to roll slightly better.

3. Bicycle tyres with tread are only beneficial on soft surfaces, not
on tarmac.

"Andre Jute" wrote in message
...
Simon Brooke sent three separate statements
each requiring explanation:

1. Contrary to common opinion, for any given rubber compound, (on
bicycles) slick tyres are better in the wet than tyres with tread.

2. They also tend to roll slightly better.

3. Bicycle tyres with tread are only beneficial on soft surfaces, not
on tarmac.

Seriously? Are you that stupid not to notice that bicycle tires are just a
touch narrower than automotive tires?

On Feb 24, 6:13*pm, Andre Jute wrote:
*Simon Brooke sent three separate statements
each requiring explanation:

1. *Contrary to common opinion, for any given rubber compound, (on
bicycles) slick tyres are better in the wet than tyres with tread.

2. They also tend to *roll slightly better.

3. Bicycle tyres with tread are only beneficial on soft surfaces, not
on tarmac.

#s 1 & 3 are obvious on their face.

In the case of 1, slick guarantees more contact with the road. Bike
tires are too narrow to hydroplane, so there's no need for channels to
evacuate water.

As for #3, on soft surfaces, the ground deforms in deference to the
tire. On hard surfaces, the tire must deform in deference to the road.
So a slick tire at pressure low enough to deform (which also increases
the contact patch area) but not bottom out provides the best traction.

I'll let someone else tackle #2, because I don't fully understand the
science of rolling resistance, and won't shame myself by, as the
Russians say, talking out my nose on the subject.

On Sun, 24 Feb 2008 22:07:18 -0800 (PST), Hank
wrote:

1. *Contrary to common opinion, for any given rubber compound, (on
bicycles) slick tyres are better in the wet than tyres with tread.

2. They also tend to *roll slightly better.

3. Bicycle tyres with tread are only beneficial on soft surfaces, not
on tarmac.

#s 1 & 3 are obvious on their face.

In the case of 1, slick guarantees more contact with the road. Bike
tires are too narrow to hydroplane, so there's no need for channels to
evacuate water.

As for #3, on soft surfaces, the ground deforms in deference to the
tire. On hard surfaces, the tire must deform in deference to the road.
So a slick tire at pressure low enough to deform (which also increases
the contact patch area) but not bottom out provides the best traction.

I'll let someone else tackle #2, because I don't fully understand the
science of rolling resistance, and won't shame myself by, as the
Russians say, talking out my nose on the subject.

Dear Hank,

The usual explanation for Simon's point #2 is that if you carve voids
into the essentially incompressible rubber, you give it more ways to
bulge outward when pressed against the road and thus waste more energy
through hysteresis.

That is, tread grooves or blocks give the rubber more surface area for
distortion at the contact patch.

Cheers,

Carl Fogel

"Andre Jute" wrote in message
...
| Simon Brooke sent three separate statements
| each requiring explanation:
|
| 1. Contrary to common opinion, for any given rubber compound, (on
| bicycles) slick tyres are better in the wet than tyres with tread.
|
| 2. They also tend to roll slightly better.
|
| 3. Bicycle tyres with tread are only beneficial on soft surfaces, not
| on tarmac.

This has been gone over many, many times in this newsgroup. Rather than
rehash it yet again, try a google search, or simply consult the FAQ-

http://draco.acs.uci.edu/rbfaq/FAQ/8b.13.html

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com

On 2008-02-25, Mike Jacoubowsky wrote:

"Andre Jute" wrote in message
...
| Simon Brooke sent three separate statements
| each requiring explanation:
|
| 1. Contrary to common opinion, for any given rubber compound, (on
| bicycles) slick tyres are better in the wet than tyres with tread.
|
| 2. They also tend to roll slightly better.
|
| 3. Bicycle tyres with tread are only beneficial on soft surfaces, not
| on tarmac.

This has been gone over many, many times in this newsgroup. Rather than
rehash it yet again, try a google search, or simply consult the FAQ-

http://draco.acs.uci.edu/rbfaq/FAQ/8b.13.html

I have a few questions about that post.

It claims that slicks are used in all weather by most street
motorcycles. I'm fairly sure motorbikes for road use don't have slick
tyres and that it's dangerous and illegal to ride them around with bald
or slick tyres. If you watch the Moto GP on TV, as soon it rains they
all start falling off and dashing into the pits for their "wets" (which
have treads).

I believe bicycles don't aquaplane. Cars rarely aquaplane either, but
relatively un-worn treaded tyres grip much better for basic braking,
traction and cornering as any driver will know from practical
experience. So why is the same effect not possible on a bicycle? I'm
thinking in particular of 47mm road tyres at 60psi or so, rather than
23mm at 110psi.

The article says, "Tread patterns have no effect on surfaces in which
they leave no impression. That is to say, if the road is harder than the
tire, a tread pattern does not improve traction". There follows a
parable about window-cleaning squeegees to demonstrate that it's
impossible for a tread to push water out of the way.

But if all that's true, then why are treaded car tyres better? They
certainly aren't harder than the road either.

It's claimed that "machines that measure traction show that smooth tyres
corner better on both wet and dry pavement". Does anyone know any more
about these tests, and what sort of tyres were tested?

Mike Jacoubowsky Wrote:
"Andre Jute" wrote in message
...
| Simon Brooke sent three separate statements
| each requiring explanation:
|
| 1. Contrary to common opinion, for any given rubber compound, (on
| bicycles) slick tyres are better in the wet than tyres with tread.
|
| 2. They also tend to roll slightly better.
|
| 3. Bicycle tyres with tread are only beneficial on soft surfaces,
not
| on tarmac.

This has been gone over many, many times in this newsgroup. Rather
than
rehash it yet again, try a google search, or simply consult the FAQ-

http://draco.acs.uci.edu/rbfaq/FAQ/8b.13.html

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com

There's one thing there that I've been thinking about every time this
discussion comes up.
-Tread patterns have no effect on surfaces in which they leave no
impression. That is to say, if the road is harder than the tire, a
tread pattern does not improve traction. -
I'll readily accept the statement that a slick tyre has better traction
than a treaded tyre against a smooth surface.
But what if the tread pattern roughly matches the surface structure of
the road surface?

It'd be a bit like having two corrugated surfaces interfacing with each
other, with a lot of protrusions interfering with each other.
Shouldn't that be grippier than one corrugated surface resting agains a
flat surface? - as long as tread courseness "matches" surface
coarseness...


--
dabac

Ben C Wrote:
.. If you watch the Moto GP on TV, as soon it rains they
all start falling off and dashing into the pits for their "wets"
(which
have treads)
Speculating wildly here, but wet weather tyres are so much softer than
the ordinary tyres that maybe they need the grooves to deal with some
other aspect of the tyres behaviour? (thermal, squirming or something?)

Ben C Wrote:
.. But if all that's true, then why are treaded car tyres better?
I believe it's mostly to do with hydroplaning. A car wheel travelling
through water quite easily generates a significant bow wave, and the
treads make it possible to drain some of that water rearwards instead of
having to push it all out of the way forwards.

Ben C Wrote:
..relatively un-worn treaded tyres grip much better for basic braking,
traction and cornering as any driver will know from practical
experience. There are a bunch of unknowns in such a comparison, so I don't know how
useful it is. But my personal theory is that the friction explanation
might be a bit simplified.
First you have friction as the "pure" surface phenomenon, but then you
also have friction as generated by a sheer mechanical interference fit
between two coarse surfaces - like dragging the business surface of a
waffle iron over another waffle iron.


--
dabac

dabac Wrote:
There's one thing there that I've been thinking about every time this
discussion comes up.
-Tread patterns have no effect on surfaces in which they leave no
impression. That is to say, if the road is harder than the tire, a
tread pattern does not improve traction. -
I'll readily accept the statement that a slick tyre has better traction
than a treaded tyre against a smooth surface.
But what if the tread pattern roughly matches the surface structure of
the road surface?

It'd be a bit like having two corrugated surfaces interfacing with each
other, with a lot of protrusions interfering with each other.
Shouldn't that be grippier than one corrugated surface resting agains a
flat surface? - as long as tread courseness "matches" surface
coarseness...

It has the likelihood to improve traction (there tend to be a lot of
variables present to preclude and unconditional statment). The tread
can interlace and get a little side bite with the non-smooth portions of
the road.


--
meb

Andre Jute Wrote:
Simon Brooke sent three separate statements
each requiring explanation:

1. Contrary to common opinion, for any given rubber compound, (on
bicycles) slick tyres are better in the wet than tyres with tread.

2. They also tend to roll slightly better.

3. Bicycle tyres with tread are only beneficial on soft surfaces, not
on tarmac.

Most road bike treads are designed to minimize spray from the wet road.


--
meb