[geeks] Drum versus disk brakes vs. rear-wheel anti-lock

[Joshua D Boyd]

On Tue, Mar 12, 2002 at 09:58:53PM -0800, Kurt Huhn wrote:

> Okay - lets try to meet halfway here.  The coefficient of friction never
> changes it is a constant - physical fact.  However, other factors do
> change - weight, force, vector of said force, etc, all combine with the
> coefficient of friction to change the *actual* frctional force applied
> to the pavement by the tire.  You are correct though, the harder two
> surfaces get pressed together, the greater the frictional force (*not*
> coefficiant of friction) is.

That isn't entirely true.  The coefficient of friction can (and often will)
change when the temperature changes.  And, as more force is applied to the
brakes, they are going to be heating up, changing that coefficient. Reality 
is a pain sometimes, ain't it.

Actually, I just reread the original post, and my understanding is that when
the brakes heat up, the c.o.f. decreases, so this still doesn't support the
original posters theory.
 
> Increased frictional force - the CoF never changes.  The CoF is a value
> given to any given material in order to calculate the frictional force
> of CoF, surface_area, force, vector of force, etc - in an equation I
> can't recall, but probably readily accessable via Google.

Well, this would be kinetic friction here, so |F|=mu*|N| where N is the 
normal force and mu is the c.o.f.  Of course, the direction of f along the
plane, sorta opposite of the direction the original force is coming from.
 
-- 
Joshua D. Boyd