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post #1 of 10 (permalink) Old 03-30-2002, 07:07 PM Thread Starter
 
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Maximum tire traction

On dry pavement, when is maximum tire traction achieved and why.

Disregard warming up the tire and assume normal tire pressure.
Andy is offline  
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post #2 of 10 (permalink) Old 03-30-2002, 07:50 PM
 
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Is this a trick question? I thought that the friction generated by performance tires was a sort of unexplainable thing like "is light a particle or a wave" sort of thing and even quantum scientists would like to stay away from the theory involved, ever since dragracers started going quicker than they were supposed to according to the laws of physics.

I have a bit of experience with auto racing and in one of either the Carroll Smith, or Van Valkenburg books it is mentioned that tire grip is at its highest when the tire slippage is enough so that the old used up rubber is being torn off to expose fresh rubber to the pavement at the rate that it takes the new rubber to become old rubber, which isn't all that long during conditions of peak traction, I don't know WTF I am talking about but I think I remember 2% slippage being mentioned and that was about tires made in the 70s, and when I say rubber I don't mean rubber, but what the tire is made of, whatever that might be. I don't know what the answer is but I don't think the tire manufacturers, if they knew would share it.
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post #3 of 10 (permalink) Old 03-30-2002, 08:31 PM Thread Starter
 
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Hi Lt.Gustl,

You got it! I will quote the parts you wrote that explain it the best. "rubber is being torn off" and "2% slippage". I'm not sure of the exact slipage, but it is just a little. I will add that the tire must still be rolling.

Next question... If you are skidding the tire, that is the tire is NOT rolling, why does traction decrease? You are tearing off rubber as stated above. For example, you are going 100 MPH and you lock up the rear tire.

Andy
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post #4 of 10 (permalink) Old 03-30-2002, 09:25 PM
 
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Is it because you are tearing off rubber faster than the 2% ? Or is it because the tire is just skimming the top of the road, and not forming to the texture of the pavement? Tires are soft so that they sort of sink onto the pavement right? Just a thought....
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post #5 of 10 (permalink) Old 03-30-2002, 09:33 PM
 
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Quote:
Originally posted by Andy
If you are skidding the tire, that is the tire is NOT rolling, why does traction decrease?
I'm a' guessing cause you're generating 'too much' heat. Heat contributes to traction up to a point: once you've started sliding, I'd imagine you've passed the point of optimal traction due to excessive heat being generated.
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post #6 of 10 (permalink) Old 03-30-2002, 09:37 PM
 
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I think Basicblur has a good point. Too much heat will melt a small amount of the tire so it would be like riding on liquid rubber. (kind of an extreme example though)
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post #7 of 10 (permalink) Old 03-30-2002, 09:55 PM
 
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Sliding friction is always greater than static friction, except in the case of a few things that exhibit this "law" in the wrong way, like that viscous fluid stuff, the tires still have friction with the road surface, just not much. Although the same people who say this can't explain why wider tires have more friction than wide ones, but tests have shown it true.

If anyone can find a traction graph of Cf vs %of slip it would be cool, especialy a newer tire, maybe two one of a race and the other street.

I have always been in the "when in doubt gas-it" group and it has gotten me out of trouble on two and four wheels, once though I overdid it and it resulted in a big burn out at speed in my car which spun around a bit while I had it floored, thinking "just a little more gas" so that I can get the weight transfer for more traction, thing is though is vaporizing rubber is a better lubricant and smokescreen than anything else.

One thing I have noticed is that slippage is best for traction on dirt and ice, and they are using a lot more slip, and wear is detrement to the performance of studs and dirt tires. So why is that? I imagine there are no hard numbers as the speedway and flattrack guys are so anti-technology and more old school.
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post #8 of 10 (permalink) Old 03-30-2002, 10:04 PM
 
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I think that "slippage" is good in mud because the spinning causes the dirt to fly out of your tires; it basically cleans you tires so that they will bite the next time they get on the ground. If you are on clay, it would take a lot more spinning to clean your tires than on dry dirt because the clay sticks in you treads. I don't know if the same thing works on ice though.
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post #9 of 10 (permalink) Old 03-31-2002, 01:54 AM
 
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Quote:
On dry pavement, when is maximum tire traction achieved and why


I would say when Troy Bayliss is riding my bike....coz he is better than me





ps : the same would apply to wet pavement, and quite possibly dirt.
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post #10 of 10 (permalink) Old 03-31-2002, 06:38 AM Thread Starter
 
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Hi Basicblur & Ninjabeater,

You are both correct! Ninjabeater said it best... "it would be like riding on liquid rubber"

Andy
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