![]() ![]() They are most commonly pneumatic (i.e inflated with air), and the result is a substantially stiff rolling structure, with the rubber generating adhesion as well as mechanical “interlocking” with the asphalt, with the result being friction.Why do tires matter? Put simply, they are the only link of the car with the ground. I'm not near my spreadsheets right now, but you should see some numbers around 1.5 to 1.8.Tires are rubber based, with metal cords to re-enforce the structure both on the contact face, and on the vertical “side walls”. Use a simple FBD to back out the dynamic weight transfer and thus the weight on the rear tires. ![]() ![]() Use the weight of the vehicle to determine the force the tires applied. Assume acceleration is constant for that period of time (not a bad 1st pass approximation from some data I've collected). This is a very dynamic situation that I have struggled coming up with a good model for.Ī good first step might be to look at 60' times for the tire of interest. However, what about the first tenths of a second during a launch where the rear tire can be at 20-30 mph while the vehicle is only moving ~5 mph. Normal slip ratio curves such as those for a stiff road course tire, show a peak in longitudinal force around 10-15% slip, with a steep fall-off in tractive force beyond this. This gets greatly muddied when talking about a drag tire. A first simplifying assumption though is that the driver can maintain the tire at the optimum slip ratio for peak tractive force from the tire. Instead it is going to be a function of longitudinal slip ratio. The trouble is that normal tires to begin with are fairly non-linear and there is no 'real' coefficient of friction in the traditional sense. However, there are several approaches that can be used to deduce an 'effective' friction coefficient from measured track data (or even general everyday observation). Unfortunately, I doubt anyone is going to have any actual measured data - and if they did, I'm sure they are not in a position to be posting it publicly. ![]()
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