Quote from Skim83:
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There is obviously more contact area. The contact that a tire has with the road is basically a square patch. A wider tire means a wider square, or a rectangle. This means more contact. When I say wider tires I mean width as when your eye level with the car from the front and measuring the tire from left to right.
I mean think about it this way. A tire that is 4 inches wide. Now think about a tire that is 1 mile wide. The 1 mile wide tire has more contact with the road. Maybe we are thinking differently or something but I don't see what you're saying when you say wider tires doesn't create more contact.
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Skim,
Using more general terms, here is another explanation of why Ken (NSXtasy) is correct:
Gravity is what pulls the car down. The amount of force is based on the car's weight. The tire pressure is what provides the "resistance" - holding the car off the ground. Assuming weight and tire pressure remain constant, a car using wide tires does not have any more "downward force" than when it uses narrow tires. The only difference is what part of the tire is touching the ground (more width means less depth is touching).
A crude example would be like comparing a waterski (long and narrow) to a wakeboard (short and fat). If the same person were to ride each of them then the same amount of surface area would be touching the water in both cases; regardless of the shape of the ski. The reason is his weight (like the car) is constant and the water (like the tire pressure) is constant. Only the shape of the ski has changed (representing a wide vs. narrow tire). His body cannot provide any more "downward force" on the wider wakeboard than it can on the narrow waterski. Therefore a wider ski would not indicate more ski was touching the water. It would only mean more WIDTH of the ski (and less DEPTH) was touching the water.
The same is true for tires. Either a long and narrow section of the tire will be touching the ground, or a short and wide section. Either way, the same amount of rubber is actually touching the ground.
Hope this clears things up a bit.