In article <
[email protected]>,
[email protected] says...
> David Kerber wrote: "Agreed; my poorly-stated point was that if you have enough braking power to
> lock up a wheel, it doesn't matter if you have cantilevers or old-style center pulls, your brakes
> no longer have any effect on your ability to slow down; it's all in the tire after that point."
>
> For the rear tire but not the front, which is still rolling. The front brake does most of the
> stopping.
It applies to any tire, not just the rear; once you lock up the front, stronger brakes won't help
you any more (though a parachute might <Grin>). With some careful modulation practice, a rider
should be able to keep both tires at just below their lock-up point for max stopping power. If your
bike geometry and weight distribution was such that you could skid the front tire rather than
flipping over it (recumbent?) if it locks up, then your tires really start coming into play.
> > Tread is a major factor in this because (1) a treaded tire arrives at the point of skidding
> > later than a smooth one and (2) once it starts skidding, there is more friction between tire and
> > pavement.
>
> "Then how come ALL race cars use slicks as long as the pavement is dry? I would think that a slick
> *of the same size* would give you better stopping power than any treaded tire because there's more
> rubber touching the road. Of course the sticking point is that usually bicycle slicks are small,
> high pressure tires designed for light weight and low rolling resistance for high speeds, while
> treaded tires are larger, lower pressure tires designed for off-road or bad-weather traction. If
> (and it's a big 'IF') you could get a slick of thesame size and pressure as a knobby MTB tire,
> I'll bet it would stop you better than the knobby would on dry pavement."
>
> It's an interesting question. Hell if I know. I do know that racing slicks are made of very soft
> rubber. When it starts to rain, and the coefficient of friction goes down, they switch to tread.
> If we follow your logic to its conclusion, they would want even smoother tires when the track gets
> slippery.
Not if the slipperyness is caused by water, sand or something else between the tire and the solid
road surface. The very soft rubber allows the tire to interact with even the smallest irregularities
in the pavement surface, as well as getting some true adhesion effects. A thin layer of water
prevents the tire from contacting the road surface at all; unless the water can be pushed out of the
way to allow the rubber to interact with the microscopic roughness of the road, the tire just rides
on a thin film of water like hydroplaning. The spaces between tread blocks give the water somewhere
to go, so it doesn't stay between the rubber on top of the blocks and the road.
> Racing is a tension between speed and traction.
>
> Asphalt pavement is not smooth. It is composed of little rocks that are stuck together. On a bike,
> little tread features interact with the little rocks, and slow the bike down, wheareas my smooth
> tires skim right over the top.
For this to work, ISTM that the size of the tread patterns would need to be on the order of the size
of the irregularities in the road, which is pretty small. On asphalt, the texture is often somewhat
rougher than concrete is. Take this to its logical extension and tell me if you think your treaded
tire will give you better traction on a polished wood floor like a gym floor or an indoor velodrome?
I'll bet a slick will be MUCH better there.
--
David Kerber An optimist says "Good morning, Lord." While a pessimist says "Good Lord,
it's morning".
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