You'd be doing a double pump to get your front brakes to work. Disk brakes
disengage because the seals stick on the pistons. When you apply the
brakes the pistons shove the pads onto the disk, when you release the
springiness of the seal lip withdraws the pistons a little. Sounds kind of
hit or miss, but that's how they work. Usually you need some residual
pressure in the front brakes to keep the pistons from withdrawing so far
that you need to pump the brakes--there's a lot of fluid volume behind a
brake piston. Are you experiencing real drag--that is enough to heat the
disk when you drive the car and don't brake, or are you just talking about
when it's jacked up? If that's the case then the problem is that you don't
have a problem. Disk brakes that are adjusted right don't spin
freely--they drag. If they don't drag it's usually because the rotor has
so much run out that it's kicking the pads back, or the residual pressure
valve isn't working.
In other words, some drag good. Too much drag bad. No drag bad.
If you are getting pull to the side, or the rotor is getting hot, then you
might want to make sure your caliper piston seals are in good condition
(not hardened) and you might make sure the residual pressure valve isn't
goobered up, though they usually fail the other way--they leak off the
pressure too quickly. It's basically a minimum backpressure check valve--a
piston valve and spring arrangement that closes when line pressure drops
below a set value.
-----Original Message-----
From: Wes Dayton [mailto:wdayton@attglobal.net]
Sent: Monday, July 30, 2001 3:42 PM
To: Friends of Triumph
Subject: Brakes not releasing
I've had a problem with the 3A's brakes not releasing completely. New
pistons etc haven't helped, and it seems to be worst on right disk. I
am beginning to suspect that thing that sits on top of the 5-way
connector. Moss book calls it a "restrictor valve" and my guess is that
it's sticking or something.
What's it do? Any idea what would result by just eliminating it?
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