Re: brake lever excessive travel

["Gregory D. Girard" <ggirard@xxxxxxxxxxxx>]

Jim,
I think it comes down to the fact that worn pads means the pads must travel
more distance to "hit" the disk, thus the volume of the system increase
while the displacement of the master cylinder stays the same. Whatever this
problem is, my wife's RS does not have it. Great Brakes!

Greg

>    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
>                 _\_  ~-.`--'_.-'   me all the TZ250's and Dunlops I need
>                / /\\    \--'_ \\   to survive for a year.
> '99 Sprint ST  \__/ `---'  \__/                            -- Roger Ford
>
>
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