On Sat, 08 Jun 2013 23:45:42 -0400, wrote:

On Sat, 8 Jun 2013 18:52:39 -0700, "PrecisionmachinisT"
wrote:


"BQ340" wrote in message
s.com...
On 6/8/2013 9:07 PM, PrecisionmachinisT wrote:
"Ed Huntress" wrote in message
...
On Sat, 08 Jun 2013 14:56:23 -0500, Ignoramus20041
wrote:

On 2013-06-08, Bob Engelhardt wrote:
On 6/8/2013 12:05 AM, Ignoramus29060 wrote:

... I just replaced the rear brake pads for the
first time in my pick-up truck, at 88,000 miles. The front brake
pads
were less than half [worn] and did not need replacing.
...

That's interesting: on every vehicle that I (or my wife) have ever
had,
the front brakes wear 2 or 3 times as fast as the back. 'Cause that's
where the weight is - especially on stopping, with the inertial weight
transfer. Do you generally have a lot of weight in the back?

Not really. It is a pick-up, most weight is in front. Actually what
you said does not make sense.

In most vehicles, front brakes wear far faster than rear brakes. And
it's because the weight shifts to the front upon braking. It applies
even to rear-engined cars.


Brakes not bear any vehicle weight; that is what axle bearings are for.

Brake wear is due solely to torque, which is going to identical on all
four
wheels until one of them locks up.

Is that true allowing for the proportioning valve front/rear pressure
difference? I would think less pressure on rear = less wear?


The cylinder with the higher pressure will lock up first, given identical
road traction and shoe contact surface area at all four (assuming that dual
wheels aren't being used)

Assuming the cyls are the same size - which they virtually NEVER are.
Less pressure in the rear is a very bad situation; you cannot steer an arc
if the front wheels lock up, it'll just keep going straigt forward no matter
which direction you point the front wheels.


A whole lot worse to have the rears lock up first, letting the rear
slide uncontrolled past the front which is still firmly planted to the
road, and slowing down. If the fronts lock first, the rears drag
behind, giving stability and allowing you to release the brakes enough
to let the front wheels hold again before the rear wheels BECOME the
front wheels.( which happens failrly quickly if the rears lock up
first - particularly on a curve. Terminal oversteer.
MikeB

--
Email is valid


This would be a good place for some of those vector diagrams they use
to explain tire adhesion, cornering, braking, and accelerating. They
make the whole thing brilliantly clear.

Or you can go take an old Corvette around a track and see how many
different ways you can spin out or swap ends. It's amazing. g

--
Ed Huntress