Calculating car tyre forces - slip ratio

[amushrow]

In most tyre models we look at the slip ratio between the tyre and the road to help determine the amount of force that the tyre can generate. My question is, why is it the ratio that is so important?

If a vehicle is doing 100m/s and the tyre is at 90m/s then the relative velocity against the road would be 10m/s and the slip ratio would be 10%
If the same vehicle was at 50m/s and the tyre at 40m/s then the relative velocity would still be 10m/s but the ratio would now be 20% which would change the amount of force that the tyre is generating.

From the tyre's perspective wouldn't both situations be the same?

 

[LightHero]

Why is the ratio so important?The ratio is important because it helps to measure the amount of friction between the tyre and the road. The higher the ratio, the less friction there is, and the less force the tyre can generate. This is important to help determine how much traction the tyre has on the road, and how much control the driver has over the vehicle. It also affects the amount of grip the tyre has when cornering, which impacts the vehicle's cornering ability.