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Old 05-25-2008, 09:54 PM   #34 (permalink)
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tires really are very complex especially modern tires. from the compound to the belts, and other materials and layers within the tires. modern tires are radials so they bulge a bit at the bottom the part of the tire that hits the ground is flat for several inches front to back, so your contact patch on a tire thats 5 inches wide that has 4 inches front to back would be like 20 square inches per tire.

trikkonceptz ;If the underlying argument here is contact patch why not test it. Take YOUR tire down to 36 psi or whatever, lift the car, roll some water based paint over the tread and drop the car on some heavy duty paper. Then re-inflate to YOUR max psi and repeat, then measure. If the patches are the same, case closed right? This should even show weight distribution by how much of the treads are printed on the paper, to see which treads are making contact and how much.
the static contact patch is different from the dynamic contact patch ie when you go around turns and accelerate and brake the load changes on the tire and the sidewalls flex quite a bit in a hard corner with the right pressure your tire will actually use some of its sidewall thats why the treads curve over the edge a bit and are not just on the bottom of the tire. if your over inflated you might get scalloping or the center might wear down etc... I am not saying i know exactly the type of negative tire wear that will happen.

and its all relative 5psi over max maybe theres no difference 20psi over max i bet you see something.

also thats why I brought up taking your tires temperatures before I do it for racing its a very valuable tool for figuring out how your using your tires.

also as your car leans into a turn your suspension flexes the inside wheel gets positive camber and the outside wheel negative caber so the car leans out and the tires rubber actually flexes the whole tire sort of moves left and right on the actual wheel, if your tires are too hard I don't know what that might do to cornering ability I will try to contribute actual numbers on tire temperatures vs pressure when I have a free day. I can take some readings under inflated , inflated properly, and over inflated. that will at least provide some data to back up what im trying to express however poorly in text.
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