BRZ/86 stopping distance

[Transport3r]

Originally Posted by Ultramaroon

No. Mu is shorthand for frictional coefficient. Higher "mu" simply lowers the pedal force required to achieve the same reactive torque required to counteract the wheel torque, which is limited by tire grip - also with its own mu.

I'm not a tribology expert but I don't remember seeing a speed component affecting dynamic coefficient of friction in any of my related studies.

It changes with velocity, but the curve is highly dependent on the material combination.

Rubber on asphalt:

[Ultramaroon]

Originally Posted by Transport3r

It changes with velocity, but the curve is highly dependent on the material combination.

Sure. In this context especially, temperature has a huge effect, but let's be clear. All other conditions being equal, speed is negligible.

I need more info to interpret that graph. Not discounting it, just... for instance, if it's expressing speed logarithmically, while I see your point, I think it also supports my argument for neglecting it.

[ZDan]

Originally Posted by Transport3r

It changes with velocity, but the curve is highly dependent on the material combination.

Rubber on asphalt:

What in the Christ? In the context of the grip between a car's tire and the road, static or sliding, this makes zero sense. Does the scale really go from 0.000000000001 m/s up to 10,000 m/s?!

In the real world, with no downforce, tire grip on the road (effective coefficient of friction) isn't a strong function of speed.

[Stonehorsw]

Originally Posted by Ultramaroon

No. Mu is shorthand for frictional coefficient. Higher "mu" simply lowers the pedal force required to achieve the same reactive torque required to counteract the wheel torque, which is limited by tire grip - also with its own mu.

I'm not a tribology expert but I don't remember seeing a speed component affecting dynamic coefficient of friction in any of my related studies.

Friction coefficient is dependent of speed, temperature and pressure. Good way to see that is the standard AK Master testing for brakes.

[strat61caster]

[Transport3r]

Originally Posted by ZDan

What in the Christ? In the context of the grip between a car's tire and the road, static or sliding, this makes zero sense. Does the scale really go from 0.000000000001 m/s up to 10,000 m/s?!

In the real world, with no downforce, tire grip on the road (effective coefficient of friction) isn't a strong function of speed.

Fair, the actual part of the curve that you can bookend in a car is probably a shallow slope that’s almost a straight line, but grip does change with wheelspin speed, that’s why you can adjust your lateral friction force (and thus slip angle) with the throttle when sliding.

[ZDan]

Originally Posted by Transport3r

Fair, the actual part of the curve that you can bookend in a car is probably a shallow slope that’s almost a straight line, but grip does change with wheelspin speed, that’s why you can adjust your lateral friction force (and thus slip angle) with the throttle when sliding.

I'm gonna say that curve is for something else, other than a realistic model of effective coefficient of friction between a car tire and asphalt. I mean, effective friction coefficient doesn't go from ~1 at "normal" speeds down to less than 0.2 stopped. Also, for a simplified model of car tire on asphalt, we'd wanna see mu-static and mu-dynamic(sliding). Maybe for a dragstrip launchpad mu-adh(esive). But mu-vis? Viscous? Like we're plowing through a sea of hot asphalt?!

That plot has zero to do with modeling tire grip!

AS far as lateral vs longitudinal friction force, that would be different for every tire. Some tires maintain a surprising amount of lateral grip while spinning, some lose any semblance of lateral grip when they start to slip/spin. Very very different characteristics between tires there, you wouldn't be able to have a generic curve modeling "tire rubber" on "asphalt".

In the context of this thread, straightline braking grip between tire and tarmac, on a car with no downforce, is not going to be a strong function of vehicle speed.