How do you calculate a friction/traction circle?

One like this:

http://image.automotive.com/f/images/9656996+pheader/0205_sccp_01_z+friction_circle+graph.jpg

I want to find the circle's radius which I assume would be the tyre limit. Can anyone help?

Centrifugal Force = (mass * velocity^2) / radius (1)
Coefficient of friction = Friction Force / Applied Load (2)

Can I use equation 2 to find the limit of the tyre and then use equation 1 to find the force required to keep the car within that limit and draw that on the circle to see at what speed it exceeds the limit?

Also how would I do this for acceleration and braking in straight line?