Bad timing...

Capt. Geoffrey Thorpe wrote:
"Jay Honeck" wrote in message
oups.com...

Strangely, we had changed that O-ring maybe six months ago, and the
pads were fine, then, so we now have a mystery. How did the brake
pads wear completely away so fast? To be safe, we removed the OTHER
wheel pant (more screws, nuts, banged heads) and inspected the left
brakes, and they are fine. Tons of pad left in them.

Disk brakes rely on rotor runout to push the pads back just a bit do you
don't have the pads in constant contact. If the new O ring was a bit on the
tight side, and the piston was sticking (the O ring could have worked like a
spring) then the pad would drag all the time the wheel was turning and wear
out quite quickly.

Actually, disk brakes are designed such that the deformation of the
seals causes the pads to slightly retract when pressure is released. I
suspect that the seals on Jay's brakes had hardened to the point that
they didn't deform when the brakes were applied and thus could not
"spring back" to pull back the pads.

Rotor run-out will certainly help push the pads back in, but that isn't
how they are designed to operate. Disk brakes will work just fine even
if the rotor is completely true with no run-out.


Matt