[ROVERNET - UK] P6B rear brakes

[Vern Klukas]

Having not heard back regarding if this is both or just one caliper, 
a few more comments:

One possibilty is an assembly error. If the beam (the heavy square 
bar that bridges the two studs inside the caliper and acts as the 
fulcrum for mechanism) is installed backwards, the geometry is 
incorrect but I do not think it would make a 3 mm difference.

The most likely thing is, as the previous posters have commented, 
dirt or stiff grease is preventing you from winding the cup all the 
way back, as the back spring pressure of the pawl is the only thing 
that keeps the screw from rotating with the cup. As soon as you can 
hear the the pawl start to slip, you are done.  Mind you, I have 
never had that difficulty in all my combat with Girling 
swinging-bloody-calipers. Perhaps I have just blocked the memory.

Other things that could do it?

Something in the hydraulic bore that keeps the piston from returning 
to the bottom of the bore. Piston installed upside down. Handbrake 
tappet jammed under the lifting strut or the handbrake operating 
lever installed wrong way around i.e. lefthand lever in righthand 
caliper.

If the studs have been out of the caliper I note that the repair 
procedures include a measurement there, so perhaps the studs can be 
installed too deep. Unlikely through, because P6B calipers should 
have the shouldered studs, not plain studs and spacer sleeves. Come 
to think of it, that might eliminate the possibilty of the beam being 
backwards as well.

That's all I can think of.

If you do take them apart, the workshop manual misses all the 
greasing instructions, but it is fairly self evident, all the Orings 
and bearing surfaces, a light application to the screw but no grease 
on the two dimples on the bottom of the strut that the piston and 
handbrake tappet rest against. The proper grease is not red rubber 
grease but a molybdenum-loaded grease similar to, but thicker than, 
modern day constant velocity joint grease. The red rubber grease is 
for the hydraulic piston only.

Yours
Vern

>Yes, back on this old chestnut again. I am in the process of replacing the
>rear calipers on my P6B which is something I have not done before. When I
>inserted the pads they were very tight and the disc would not move. When I
>looked at the piston inside the caliper, it was proud by about 3mm. I
>decided to bite the bullet and remove the calipers from the car and onto the
>bench for easier access. After checking the manual and rotating the piston
>clockwise it would still not move back flush with the caliper body. If I
>move the handbrake bracket, the piston rotates and clicks which would seem
>to indicate all is well inside the caliper (which has been reconditioned by
>myself and a very experienced Rover Car Club of Australia member) but I
>still cannot get the pistons flush with caliper body (it's the same on both
>calipers).
>Is it OK for the piston to be proud by 3mm? or must it be flush? Apart from
>rotating the piston, is there any other way of moving it back? All help
>would be greatly appreciated.
>Ray Wilkins
>1976 P6B
>Melbourne Australia
>
>
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-- 
Vern Klukas                             I'm a little . . .
Inkspot Type & Design
vern at inkspotco.com