Round Black Donuts, or in Other Words, Tires Part 2 Bob White ...

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Figure no. 4 Maximum Coefficient of Friction vs Load for Some Race Tires The following table is a key to the race tire legend in Figure no. 4. Table no. 1 Race Tire legend key Letter Tire Type and Size A 165 HR 15 (5 ½ J x 15)
B 245/575 – 15 slick (12 K x 15) C 265/575 – 15 slick (12 K x 15) D 215/60 VR XWX (7 J x 15) E 245/575 – 15 intermediate (12 K x 15) F 340/575 – 15 slick (15 K x 15) Notice in comparing the friction values in Figures 3 and 4 that it is important to use the same load values since the weight scales are different. For the worst race type tires the friction values are 20% or so higher than the best street values and the best race tire values are 60% or more better than the street values! For the same radius of a turn the speed increases with the square root of the mu value which means sqrt(1.6) = 1.26 or a 26% increase in speed, i.e. a 50 mph maximum turn speed becomes 60 mph with race tires. For straight line acceleration or braking the change is directly proportional to the friction value assuming the engine has sufficient torque (and correct gearing) to keep the tire at its maximum friction value. This leads to another characteristic of tires, there must be some slip between the tire and the road to produce any braking, acceleration, or turning force. For braking and acceleration the slip is ratio of the actual rotation speed of the tire and the ideal rotational speed being the rotation speed if you let the tire roll down a hill by itself. We will return to what slip is for a cornering tire a bit later. Thus, a free rolling tire has a slip of zero and a locked up tire has 100% slip. Figure no. 5 below shows how the friction varies with slip.
Page 1 and 2: Round Black Donuts, or in Other Wor
Page 3: Let’s start with friction. The co
Page 8 and 9: Figure no. 6 Tire Cornering Side Fo
Page 10 and 11: Figure no. 8 Cornering Force Coeffi
Page 13 and 14: Figure no. 10 Definition of how a C
Page 15: in it. Seems like the Germans may h

Round Black Donuts, or in Other Words, Tires Part 2 Bob White ...

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