I'm currently working out a few calculations for a physics project involving brakes and I need some somewhat accurate values for the brake pads ---> Axxis Ultimates.

I think it should be somewhere around .50 or something. They are gripping Brembo OE rotors.

Also, how about Falken Azenis? I think they should be around .85-.90.

Any thoughts?

thanks

 

I think you will have to contact the manufacturers for exact figures, but one of my engineering handbooks lists the following:
Rubber tire on pavement: 0.40 dynamic, 0.55 static
Asbestos brake lining on steel: 0.11 dynamic, 0.15 static.

Hope that helps.

 

Hmmm...

I keep finding results varying from .1 to .7 for brakes, and .4 to 1.1 for tires.

I would expect the Ultimates to probably be somewhere on the upper 1/4 of the spectrum. I'm probably going to stick with .52-.6.

As for the tires, I am getting experimental values around .65 dynamic.

 

If that were true, peak acceleration (in the physics sense, including deceleration and lateral acceleration) would not exceed 0.55g. But typical car tests report braking around 1g and lateral acceleration of > 0.8g.
Is your handbook old (from a time when street tire compounds were not so good)?

 

Handbook's new, but data could be old. The figures might be conservative.

 

You can basically just use the cornering force + a little bit for the tires, as that's a good measure of what the friction coefficient would have to be to generate said numbers. Although come to think of it, with a tire sliding across the ground generating grip it's really a coefficient of shear and not just friction. Also you'd technically need to take into account aerodynamic forces acting to load or unload the tires.

And .5 would be a very good street pad coefficient estimate. Of course what it actually is at any given measure would depend primarily upon surface temperature.

 

I'm using low speeds to create shorter and easier measured stopping distances. To avoid wind resistance, I calculated it at the speeds we were using and "proved" it was insignificant.

I'm going to keep our .65 value. I have no data to generate a cornering force, and I don't want to deal with different contact patch shapes anyway.

I did come up with some pretty neat information about the tire forces before the tires lock (ignoring brake booster).