87 accord brakes

My 87 2.0 exi alb accord has failed its test for rear brake imbalance. Both
service and parking brake appear to be grossly deficient on the right rear.

Problem is I cannot find anything wrong! Piston, calliper cable etc are all
totally free and in good order, there are no fluid leaks and the pads are in
good shape. The self adjusting handbrake mechanism is working fine yet still
there is a 34% imbalance between right and left.

Anyone come across this problem or have any ideas??? I am loath to strip
down the calliper for inspection as it seems to function perfectly

 

First, make certain the slider pins are all free, and that the pads are
loose enough on the mount bracket that they will fall off if the caliper is
removed.

Second, inspect the anti-squeal shims on the backs of the pads. If they are
rusty, you will have a situation where the piston must compress the rust
before being able to apply braking action, and of course, one will compress
before the other...

Third, try to turn in the pistons with a large screwdriver. It should take
a bit of effort to start, but should thereafter turn smoothly and fairly
easily. You should find similar effort needed on both sides. Watch that the
dust boot does not twist and split!

Fourth, pull one of the the calipers off the mounting bracket. Have someone
step on the brake while you watch the piston move (will only move about
1/16" or less with each press). It should move out a bit, then pull back in
again once pedal pressure is released. Make note of the distance.

**ONLY STEP ON THE PEDAL AS FAR AS IT WOULD MOVE UNDER NORMAL USE** or you
risk tearing up the master cylinder seals. A block of wood under the pedal
will serve as a hard stop.

Now put that caliper back, remove the other one, then compare the first to
the piston movement on the other side.


One of the foregoing will point up the problem. It's a bit silly that the
MoT tester is not allowed to visually inspect the brakes with the wheel
off.

 

Thanks Tegger but tried all that & everything is free/same as other side.
One thought I had that u might like to comment on is that it could be air in
the system (as far as the footbrake is concerned) since it is a dual circuit
system. Still wouldn't answer the handbrake question though

Ian