thanks, well you are right... you need to use these coefficients to find the actual friction
here is a snippet from the book I'm reading...

For Static Friction:

Fs = MUsN (the s's are meant to be subscripts)
(N = the normal force)

For Kinetic Friction:
Fk = -MUkN (the k's are meant to be subscripts)
(N = the normal force)

to find normal force convert the weigth of the object on the surface to newtons, then multiply it by -1 (this should yield a positive number)

So to find friction...
i.e. for a racing game rubber on dry concrete:
The car weighs 1.5k pounds ---> -6672.6N
the normal force = 6672.6N

Static Friction = -1.0(667.6N) = -6672.6N

Kinetic Friction = -.9(6672.6N) = -6005.3N


if anyone out their wanted to know..
I still haven't delved to far into the physics engine yet...