Re: brake lever excessive travel

[Jim Gillespie <jim@xxxxxxxxxxxxx>]

    I have a theory.

    Background: some time ago I was talking to a friend of mine about my
perceived problem with the ST's brakes.  He had had a similar problem
with a ZXR750 which was eventually traced to the seals on the calipers.
I knew even less then than I do now about how brakes work, but for some
reason it has just clicked in my head.

    As I understand it, the pistons don't usually slide past the seals,
instead when the brakes are applied the seals deform to allow the pads
to contact the disks, and when the pressure is released the seals pull
the pistons back into the caliper a little to reduce drag.  As the pads
wear, the pistons move past the seals a little so that the gap is
maintained.

    What if the seals are holding onto the pistons just a little too
tightly, so that they don't move past the seals so easily?  As the pads
wear, lever travel increases.  Eventually, the gap between the pads and
the disk is so great that the pistons move past the seals, but only a
little bit.  A stable state is reached, with greater lever travel but
the same overall force (I think).  After the pistons are cleaned, they
move more easily past the seals.

    Comments?

                Jim
- --
      jim@         ,'_              I vote for a communist state where I
  gillespie.org   / -.--.    ___    work for the government and they give
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                / /\\    \--'_ \\   to survive for a year.
 '99 Sprint ST  \__/ `---'  \__/                            -- Roger Ford


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