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Shifting weight forward in a racecar to improve turn in is a known fact. Not only NASCAR and CART crew chiefs use this phenomena but Milliken & Milliken [1]1, Carroll Smith [2], and other authorities state this fact in books. The “classic” tire side force variation with load curve at a constant slip angle shows side force increases less than load. The “classic” tire side force/load curve, which is real data, does NOT agree with the facts known to crew chiefs AND authorities in the field of tires. A different tire model that includes slip heat generation is used to show that BOTH statements above are correct, but at different times in a corner. The reason for the change in tire traction is heat generated in the contact patch and a change in surface temperature of the tread rubber.

Working NASCAR tires correctly will help a team qualify well and have a chance to win on Sunday. Aerodynamics, engines, and shocks are not the only things. Tire usage dictates suspension geometry, springs, weight jacking, and shock choices. Tire slip losses in corners are huge, over 100 HP in qualifying trim and over 150 HP in race trim. Proper tire usage reduces drag HP for qualifying and controls right side tire heating in race trim. Tire slip loss heats the tread rubber and is the primary factor limiting car performance on short tracks. Evaluation of several adjustments on tire and car cornering performance is determined using the Hallum Contact Patch Model presented in SAE 983028 Understanding Race Tires. One psi of tire pressure is significant to car performance. Tire and car performance changes with toe, Ackerman, camber, aerodynamic force, load jacking, and weight, are compared to the performance change with tire pressure.

A simple tire tread model predicts numerous tire performance characteristics. The macro behavior of the rubber gripping the road under vertical load and horizontal force is hypothesized and used to model heat generation in the contact patch. Contact patch heating explains trends of tire performance with slip, pressure, load, camber, tread thickness, and several rubber characteristics. A pressure supported radial wound toroid tire body model is used to evaluate tire deflection, spring rate, and tread momentum loss variation with speed and load. Tire deflection and momentum loss changes with speed together with slip losses can be used to optimize high speed tire performance. New insight to the true effects of camber, tread heating, tread momentum, and surface rubber sliding is presented that is not covered by other works. The new hypothesis of sliding in the contact patch, slip and re-grip, may lead to new understanding of other tire phenomena.

A theoretical model of the drag tire is presented and performance predictions of Fuel drag cars is compared to race car data. The data comparison, in both magnitude and trends, substantiate the proposed Tread Momentum principle. Top Fuel drag cars accelerate at over 4 “g's” for several seconds. The effective tire friction factor based on car weight is over four. But the average friction coefficient between the tire and the ground is less than two. The Tread Momentum principle explains how drag tire dynamics give added traction capability. High torque and power are required to generate the added traction capability. The principle can lead to improved high speed race tire performance in other fields.