RE: 105 Brake Questions

[cbrown@xxxxxxxxxxxxxxxxxxxxxxxx]

in v7n26
Date: Fri, 7 Aug 1998 15:50:08 -0400 
From: Richard Broughton <richard.broughton@domain.elided>
Subject: RE: 105 Brake Questions

<<<
1.        The pistons have a cutout notch, which the manual states has to be
set in the correct position.... 

2.        What is the function of the cutout notches. I have looked at the
assembly and I can't see why the notches are there or what they do..
Richard Broughton
Columbia, SC
1966 Giulia TI >>>


Richard,
my understanding of this is that these 'notches'  compensate for uneven wear of
the pad. Under brake application, the leading edge of the pad gets hotter,
generates gas which causes a tendency for the trailing part of the pad to ride
on the cushion of gas. Resulting in tapered wear across the pad.  The slight
cocking of the pad attitude is allowed by piston/bore clearance, and pliancy of
the seal.

The seals are shaped such that, that they distort slightly under pressure. After
release of the brake pressure, they relax and effectively pull the piston back,
allowing the pad to withdraw from the disc surface by a thou or two. This
prevents even slight contact friction, from heating the pad under normal (non-
braking) running and resultant expansion, friction and abnormal wear.

chris brown

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