Rebuilt caliper - handbrake does not adjust

[Martin Williams]

I have just had the rear calipers refurbished with new pistons etc.

Having fitted them and bled them I cannot get the offside handbrake mechanism to operate. I will talk to the company who refurbished them on Monday but in the meantime looking for any suggestions for what I could try before dismantling and sending it back!

The nearside has adjusted correctly and the footbrake is fine. The external handbrake mechanism is moving on the offside caliper .

A couple of things have seemed a bit odd which hopefully will give someone a clue.

The offside caliper has been difficult to bleed, the odd air bubble has kept coming out when I was convinced it had stopped (I have bled through over 1l now!)
I fitted new disks and pads at the same time but of course the calipers did not need winding back. To try and check the mechanism when it did not adjust I fitted worn out pads and applied the brakes. The piston did not come out far enough to contact the pads and could be pushed back in with my fingers rather than needing to be would in. Winding in made no difference to the behaviour though.
The last thing I tried was winding the piston the wrong way for a turn or so. Having done that the piston resists a straight push and seems to wind in ok as well as working correctly with the worn out pads fitted. However, still no effective handbrake despite standing on the brakes rather hard repeatedly!

Thoughts?

[Murray Betts]

Sounds very likely that either they've left something of the handbrake/self-adjust mechanism out or reassembled it incorrectly.
I vaguely recall taking one of mine apart. It was at the first MOT that it failed on having no handbrake on one side. Turned out it was simply the cable adjustment was completely wrong but in the learning process I took the piston out to see what was inside, remember that was in 1998 so my recollection of exactly what the internals look like is a little vague!! There's a helix rod arrangement with what is effectively a nut and some sort of friction spring which has some lost motion so the brake piston can move a small amount without adjusting the nut on the helix, only when it moves more does the nut wind itself along and takes up some of the slack and then stays there, hence the need to manually wind it back to reset it. Clever as long as it is assembled correctly and it works. It might well be possible to get the bits in the wrong way round for example.

[Martin Williams]

I talked to one of the technicians at the company who reconditioned the calipers. He alleged that it was because I had obviously pressed on the brake and / or pulled on the handbrake without having "wound forward" the piston to have minimal free movement before the brake was on. He said I would have to return it for them to sort out.
Since I had fitted new disks and pads I was not convinced, there was minimal clearance when I first tried to get them to self adjust. It is true that I had then put some old pads in and had both wound back and forward to try and start the adjustment.
So I then tried again, lots of winding forward and back and differing thicknesses of pads. Eventually I found a combination with no clearance at all (pretty well an interference fit!) and at last it started to adjust. Old pads out, wind back and new pads in and it still was self adjusting. Wheel back on and straight back for a successful MOT retest!
I'm still not sure why I needed zero clearance to start the auto adjustment working. Previously having wound back, either for new pads or after a routine dismantle and clean, I have not had any problems. Possibly they had the adjuster right at the end of its travel and it needed this to get it moving.

In any case the good news is it is all sorted now and it should stop eating rear pads!

Footnote on bleeding, I suspect the bleed nipple on that caliper is a little loose in its threads and I let the pedal up too quickly causing it to suck a little air past the threads. Pedal seems firm enough now.

[Collette Dobson]

A rear calliper re build is on the list for our car. You can get kits for about £60 but it is interesting you decided to send yours off for a recon. Is it a tricky DIY job?

[Martin Williams]

Hi Collette,
It should be reasonably straight forward to rebuild, though it sounds like if you need new pistons you might have to be a bit brutal to remove the handbrake adjust mechanism. I had asked for the replaced pistons back in case they become unobtainable in the future but was told they had to cut them apart to remove the mechanism! Note that Bigg Red do not seem to have a supply of pistons for the rear calipers.

The workshop manual identifies special tools to ensure you do not damage the seals on reassembly but I am sure if you are careful you can get away without them.

My main reason for sending them away was my time. I had time to swap them over but have too many other things happening to be able to tackle the rebuild. It also meant they were painted which I might not have done myself.

[Collette Dobson]

Thank you Martin - useful info.

[Murray Betts]

Considering the age of the cars now and the scarcity of parts for the rear brakes (unique to the Capp as far as I know), I recently bought a pair of rear discs and a pair pf caliper rebuild kits which include the pistons and all seals/boots/O-rings. I don't need them at the moment, but I'd sooner have some than find they are unobtainable as/when I do need them. The ones on the car are 30yrs old nearly, the spares should last on the shelf for a decade or more if kept well.
I got them from ebay, the discs are branded Kavo ref.no. BR-8737-C sold by https://www.autolinkmx5.com/brake-discs ... 8491-p.asp ,
the rebuild kits were from https://www.frentech-uk.co.uk/
I just need to get some rear pads now ..............

[Collette Dobson]

We recently bought rear pads from Impex. Couldn't find them in Europe.