"Joe Pfeiffer" wrote in message
...
Jeff Wisnia writes:

Someone asked me why their car's front brakes always seem to need
replacing long before the rear brakes do.

I started to give him the old "inertial weight transfer to the front
while braking" reply and then found that it really wasn't making total
sense to me.

Providing you don't drive and brake like a madman neither the front or
rear tires are doing much skidding on the pavement so it's likely all
four are all making the same number of revolutions while braking. So,
if the brake pad areas and the piston diameters were all equal front
and rear I'd expect the pad wear rate to also be equal.

With most cars its even more than just inertial transfer -- there's a
lot more weight on the fronts than the rears *before* you put the
brakes on.

If you the areas, piston diameters, and line pressures were equal
you'd lock up the rears before you were applying full force to the
fronts. The brake proportioning (however the manufacturer goes about
it) really does make the fronts exert more force than the rears.

The corollary I've never been able to figure out is why they don't use
smaller brakes and more pressure in the rear, so they'd all wear out
at the same time (well, as a matter of fact most vehicles I've had
apart have had larger fronts than rears. But not by enough to make up
for the difference in how hard the fronts have to work).

Why would you want them to all wear out at the same time? That wouldn't be
safe or save money.