[ROVERNET - UK] P6B rear brakes

[JULIET KEILER]

Ahh the Girling rear calpier.....surely a test of anyones love of the P6!

YES the piston should go back flush. In effect you have two parts, an externally threaded piston with a serated wheel attached and operated by the handrake lever/pawl and an internally threaded piston cup (well thats what the book calls it) which has at one end a triangular piece of steel with a small lug that the brake pad 'sits' on. This triangular 'pad support' will turn independently of the piston cup. So if your still with me...... once assembled the handbrake pawl moves the serated wheel 1 tooth at a tim, as it does so it screws OUT of the piston cup which cannot turn as the triangular shaped 'pad support' are preventing it from doing so. Result it EXPANDS the piston/piston cup and in effect pushes the pad harder against the disc taking up any wear.

In your case Ray it sounds like they've not been 'together' for some time hence rust and cr*p are probably in the void between piston/piston cup preventing it from screwing right in. I suggest you unscrew them completely and then with loads of WD40 or similar coupled with a narrow wire brush or an old screwdriver try and remove the rubbish and keep screwing/unscrewing till it seats properly. Then perhaps some red rubber grease or something similar on reassembly should keep it reasonably free.

On the basis rear pads on moderate driving may only need doing every 20, 25 or even 30,000 miles it's probaby been many years since they were screwed back in completely.

Good luck let us know how it goes.

Regards

Alan Francis (partviking)


----- Original Message ----
From: Ray Wilkins <raymond.wilkins at bigpond.com>
To: rovernet at lyris.ccdata.com
Sent: Saturday, 24 November, 2007 7:27:41 AM
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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