I’ve been wondering why sport and race cars use very wide tires for improved grip. Friction is as far as I’m aware a function of a coefficient and pressure. So, with wider tires that pressure should reduce no? Why do fast cars then use wide tires?
In: Physics
This is actually a REALLY good question. It was actually a challenge problem in one of my undergrad physics classes. You are correct, friction force is only dependent on CoF and Mass.
If you just look at the math, it seems impossible to increase the grip of tire. However; in the real world, these frictional forces are dynamic, not static.
First, many people assume that increasing tire width increases the surface in contact with the road. This is actually NOT true. What increasing the width of the tire does is increase the width of the contact surface perpendicular to the direction of travel, but it becomes narrower in the direction of travel (You are distributing the forces across a wider area and decreasing the pressure). Think of it as a 3×5 rectangle vs a 5×3 rectangle. Because of these dynamic forces and the road surface not being completely smooth, this wider contact path perpendicular to the direction of travel increases the ability of the tire to actually reach the maximum CoF.
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