zlacker

It doesn't change much, but note that unless you've blocked your wheels (and you have no ABS), you need to check the static coefficients. Wheels work so that from the point of view of the wheel the asphalt is still (i.e. there is no translation, only rotation).

This is why blocking the wheels increases braking distance: you suddenly have to deal with a much smaller friction coefficient.

>>bonzin+(OP)
Well that and the fact that rubber melts and that changes some coefficients. Nothing about braking is as simple as one formula.

P.S. Isn't the static coefficient calculated for a stationary object trying to move against a surface? In a wheels locked scenario the wheel is sliding so the dynamic coefficient is the one to look at, accounting for the changed material properties of the heated/melted material.

>>buran7+y2
Right, in the wheels locked scenario the dynamic coefficient is the one that matters, it's smaller than the static coefficient and that leads to a longer braking distance.

For a rolling wheel however, the stationary object is ideally just a point of the wheel, trying to move against the surface; but as soon as the wheel wins against the surface, the point rotates away and a new point tries to move against the surface. Even in the less ideal case a point of the tire always touches the same point of the asphalt from the moment it touches the ground to the moment it leaves it. So in that case you use the static coefficient.

For a more visual explanation see https://youtu.be/J0PVm4XTGeY?si=20TygSRdH3UxIx_4

>>bonzin+S6
We'd probably be better off using the "sliding/rolling" terminology which is analogous but clearer and more intuitive when dealing with wheels.

>>bonzin+(OP)
> Wheels work so that from the point of view of the wheel the asphalt is still

In order to create a longitudinal force, the tire must have non-zero slippage. It’s not large (for typical mild driving), but it’s not zero if you’re using the tire to accelerate or decelerate the car.

Max acceleration forces are found around 10% slip ratio.

http://www.insideracingtechnology.com/Resources/bhvrdrvbrksl...