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
Tyres do various jobs and their design is a compromise of those things. As a general principle, you want enough surface area to be able to perform that function properly, but not too much or you have excess / unnecessary friction.
When you accelerate, you want your driving wheels to transfer as much rotation as possible from the wheels to the road. More surface area = more grip = more rotational force transferring to the road = more forward movement. The more power you have, the wider your tyres are (up to a point). If you don’t have enough grip, you break traction and your wheels spin without actually pushing you forward.
For your steering wheels you wants wider wheels for more grip so you turn more accurately. If your steering wheels lose grip, they can turn relative to the car but they won’t move the car relative to the direction of the road. Similarly for braking, wider tyres offer more grip which means better braking.
Tyres also have tread that pushes water out of the way. The more tread lines you have, the less rubber you have in contact with the road. Your grip is reduced (for acceleration and turning and braking) but you can push more water away which improves grip. Most high-level racing uses slick tyres because they have the most grip for the width of the tyre, but they are terrible in wet weather, so there are other tyres for those conditions. As I said, it is a compromise.
The limit here is that you don’t want your tyres to be too wide or you have “too much grip” and you end up wasting / losing too much speed due to friction. This would make it inefficient / pointless.
The current setup is a carefully calculated compromise to harness as much of the vehicle’s capacity without wasting it through having to overcome the additional friction.
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