From: utzoo!watmath!watcgl!dmmartindale
Newsgroups: net.auto
Title: Re: Backing up to even out brakes
Article-I.D.: watcgl.182
Posted: Wed Feb  9 11:54:35 1983
Received: Thu Feb 10 00:19:57 1983
References: alice.1473

As Keith Bauer explained, disk brakes are self-adjusting because as the
pads wear, more fluid from the master cylinder reservoir takes up the
extra volume in the wheel cylinder.  Since the pressure on the pads
is applied solely by the hydraulic cylinders, this is enough to handle
all the wear that occurs.  In drum brakes, the shoes are supported at
two points - one at each end.  One of these is the hydraulic cylinder,
and the same sort of automatic adjustment takes place here as with the
cylinder in disk brakes.  The other end, though, is supported by a mechanical
stop of some sort, and this also has to be adjusted to compensate for wear
of the shoes.  Various manufacturers do different things to provide this
adjustment.  Some cars have no automatic adjustment at all, so the
adjustment is done manually from time to time.  Many of the American cars
use a mechanism where when you apply the brakes while backing up and the shoes
move more than a certain amount, a cable tightens and rotates an adjusting
nut a fraction of a turn.  If you stop while backing up occasionally and
the mechanism stays working, the brakes stay adjusted.
The method that works on your car depends on how the manufacturer designed
the brakes - there is nothing magic about backing up and applying the
brakes.

Dave Martindale