Thomas, I believe this is the root of your problem.
Calipers came off an R1, was it wadded, a racer? Most likely the brakes
were cooked and you need to replace the caliper seals (roll back seals).
The elegant thing about a disc brake design is the roll back seal does
several things. First and foremost it seals the brake system pressure in
and allows the hydraulic pressure to actuate the piston which squeezes the
pad to the rotor giving us brake torque. Seal also keeps stuff out of the
brake system. So far all pretty apparent. The real magic comes in in how
it extends and pulls back on the piston as pressure is released. The angle
of the seal land, the break or chamfer of the seal land, the compression of
the seal, the durometer of the rubber, and the surface finish of the piston
all are variable that the brake design engineer balance to get proper
function. To prevent brake drag, the seal rolls back after pressure is
released allowing for a small amount of clearance between the piston and the
brake shoe or pad, rotor run out and bumpy roads do the rest to knock and
shake the piston free. Now the other elegant feature of the disc brake
design. As the pad wears the piston must travel further and further each
application. More magic, eventually the piston travels far enough
(stretching the seal) that the piston slips through the seal a very small
amount and establishes a new staring point. This dance of apply - stretch -
release -retract- apply - stretch - release -retract- SLIP apply -
stretch - release -retract- goes on.
Now what has all this to do with you poor lever feel? I suspect as Eric
says the seals in your caliper are "hard as a woodpeckers lips" and not able
to do the dance.
Ronald Fisch V.M.O.A. 78
86 mostly stock, [EMAIL PROTECTED]
-----Original Message-----
No check valve in a brake system . Pistons move away by elasticity of
the piston seals and this is a set design limit . If the pistons are not
retracting properly I will guarantee the the seals are hard as a wood
peckers lips . Pads move from vibration or bad rotor runout . This is
why the pins must be kept resonablly clean to get the pads off the
rotor, help in cooling, and lower the pad drag on the machine .
Eric H.
----- Original Message -----
F
> Eric,
> Without regard to mechanical alignment .. I am really wondering where
> the "check-valve" functionality went on that system. I have a really
> bad feeling that it is the job of the "little flap". A small amount of
> pressure must be retained in the lines when the lever is released to
> keep the pads from moving away from the rotor. All disc brake systems
> "must" have a fluid check valve and if it is not the "little spring
> steel flap" in the bottom of the master cylinder well then I wonder
> where it could be.
> campbell
>
>
>
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