[ROVERNET - UK] P6B rear brakes

[Roger.Matheson]

Hi Ray,
As I recall the piston does not fully retract.  However on the end of the 
piston is a flange with a 90 degree elbow bend.  This elbow engages with the 
top of the inboard pad and holds the piston while the push rod progressively 
turns in its thread increasing the length of that assembly (and ajusting the 
brake clearence).  This flange should be flush with the calliper at the end 
of its retraction.  As I recall when fitting new pads, you screw in the 
piston (referred to as the piston cup assembly) to the end of its thread in 
the push rod and until it starts to turn the rod with its serated edge 
against the ajuster pawl.  This makes a distictive noise.  However if there 
is dirt in the thread then the piston will not fully retract before turning 
the whole assembly.  With the calliper off you could unscrew the piston out 
and clean the thread without fully dismantling the calliper.  With this out 
you could also greese the rubber o ring in the calliper  In my experience 
fitting the pads with the required clearence requires two things.  Firstly 
the elbow of the flang must be at the 12 o'clock position in the calliper 
for it to properly engage over the top of the inboard pad as the retaining 
plates are positioned.  Otherwise the elbow will press up against the back 
of the inner pad pushing it too far out, creating the problem you have 
experienced. Secondly, the two bolts holding the outer pad must be properly 
engaged in the recess holes of the pad so that the metal base of the pad is 
in full contact with the calliper.  Otherwise it too will be too far out. I 
have had pads with recess holes too shallow that I have needed to drill out 
by a ml or two.  These bolts have flat washers and if you forget them, then 
again the outer pad may be positioed too far out.

Trust this helps.  I have the relevant pages in the manual and could email 
p/c's to you.

Cheers Roger
----- Original Message ----- 
From: "Ray Wilkins" <raymond.wilkins at bigpond.com>
To: <rovernet at lyris.ccdata.com>
Sent: Saturday, November 24, 2007 6:27 PM
Subject: [ROVERNET - UK] P6B rear brakes


> 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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