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[ST] Re: Brake Fix (Long)



I've been reading this thread about brakes for a little bit, and thought
it was time to throw my two cents in.  The "O" rings that seal the brake
piston in the caliper bore actually do more than just keep the brake
fluid inside.   Because they are square cut, they have a lot of surface
area contacting the piston.  When you apply the brakes, and the piston
moves out, the tension of the seal against it prevents the piston from
actually sliding out of the seal.  Instead, the seal stretches and
flexes.  When you release the brake, the rubber returns to its rested
state, and pulls the piston with it, away from the pads.  In this
manner, they act as return springs, and this is what keeps the pads rom
dragging on the rotors.  The size, shape, and seal material is chosen to
provide the desired amount of flex, and how far the pads return.  This
is felt as free play at the lever.  All of the "fixes" that I have seen
mentioned are really just forcing the piston to move out of the seal
just a bit, making less clearance between the pad and the rotor.  The
reason this is temporary is because the seals will return to their
"natural" state as the pad wears.  A more permanent fix would be to
change the seals out with some harder ones, so that they would flex
less.  Another theoretical solution would be seals with less surface
tension against the piston, so that it would slide through easier.  The
downside to these solutions is that they would cause more brake drag.
This is certainly a bad thing, as the rotors will likely suffer from the
excess heat generated.  My personal solution is to practice "panic"
stops periodically, so that I train my hand muscles to where the
friction point is.  If you try this, you will most likely notice that
the little bit of extra lever travel does not translate to "mushy"
brakes. Our brains are just trained to think this way.  Understanding
the real cause of the lever feel can help us to accept and appreciate
the  brakes on our Triumphs for the wonderful stoppers they are.  I hope
this helps.

Wes


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