Q:

Is there an upper bound on the amount of friction a body can generate?

Through some driver's ed class i encountered a claim stating that a car traveling at 30 kmph has a minimal braking distance of 8 meters (The specific number is not important). My question is whether there is indeed a maximum force a body can have acted upon it by friction?
The naive model I know states that given a friction coefficient $\mu$ and  a body of mass $m$, the friction force would be $m\cdot g\cdot \mu$. Is there a very strict upper bound on values of $\mu$? 

A:

There is an upper bound to the amount of static friction force that can be achieved without skidding. It is given by $f_{s}=μ_{s}N$ where $μ_{s}$ is the coefficient of static friction between the surfaces, and $N$ is the normal (perpendicular) force acting on the surface (=$mg$ for a mass $m$ on a horizontal surface).
When braking the maximum force that can slow the vehicle is the static friction force,  above which skidding will occur. Then you will be dealing with a kinetic friction force, which given by $f_{k}=μ_{k}N$ where $μ_{k}$ is the coefficient of kinetic friction. The coefficient of kinetic friction, $μ_{k}$ ,is generally less than $μ_{s}$ making the kinetic friction force bringing the vehicle to a stop less than the static friction force.
Hope this helps

