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In Reply to: What supports our cars, air or tires? posted by Bart B. on January 20, 2001 at 11:26:06:
I thought the car rode on air in the tires and all the tire did was keep that air from squeezing out from under the tire and very little, if any vertical pressure was on the sidewalls.
tires are actually quite complicated. if you were to oversimplify it, yes, the tire basically keeps the air in place (this is not too far off for a 'tubular' tire, like one on a bicycle).
with modern low-profile car tires, a better way of thinking about it is that the air pressure maintains tension on the tire walls (side and tread). by doing this, the pressure allows the tire to keep its shape, with only small amount of controlled deformation.
the properties of materials and construction in each portion of the tire determine what the shape is going to be, and how and when the tire should deform. the tire needs the support of proper amount of air pressure to do that effectively. too little, and the loads are not distributed in the way intended by the designers. this leads to excessive deformation, local overstressing, overheating, and all kinds of other undesireable things. too much pressure, and the tire is not deforming as intended, resulting in non-optimal contact patch and reduced performance. in race tires, excessive pressure may also prevent the tire from achieving the temperature it needs for its compound to work properly (my yoko 038's are like that, they like to see about 26psi hot).
fwiw.
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