Rear caliper rebuild kit

Hi all. I know some people (Custard, Clee etc) have been here before so I'm hoping someone will know.

I've ordered up a few components to allow the local garage to try to rebuild the offside rear caliper (having failed the MOT as it was sticking)

Unfortunately gta parts being what they are I've sourced a budweg piston from brakes int and a seal kit from biggred.

Looking at the two together the square section seal looks too big and even the main dust seal seems loose.

Piston is 50mm but square section seal is 60mm. Have they sent the wrong parts?

Darren ........ Are you sure that it is the piston sticking ? ....... I would be checking out the sliders first.
A quick check is to remove the brake shoes, and work the caliper back and forth a few times. they should slide smoothly, but if they are worn, they will feel rough as if there is a ridge or ridges on the sliders. Then rock the caliper on the sliders ....... there should be very little slack when trying this.
I have had this on one of mine and I did a temporary fix by lifting the dust seals slightly and squirting some spray silicone grease, via the extension tube, into each end of the sliders. Having slid the caliper back and forth, and applied more silicon grease, the slider became quite smooth to slid.
If this stops it sticking,...... as it did on mine, ..... then replace the sliders and silicone grease them before fitting.
This check can be done without removing the caliper.
John

Thanks John. No not 100% sure it's the piston, but the sliders were replaced about 6 months ago with brand new ones (they're only about 12 quid from ebay as they're shared with the BX so a doddle to source). It was fine at the time but is sticking again now.

Anyway, so next logical stop seemed to be the piston itself as it's again 'relatively' easy to replace and I was wondering if that had simply pitted / corroded as other people have seen that before.

I think I've answered my own question though, as measuring up the seals it looks like Bigrred have shipped A610 seals. Cross referencing them against designs on BrakesInt they look the same and measure up as 57mm which is 610 sized... shame BrakesInt don't have GTA seals in stock.

Phone call to Bigrred tomorrow I guess.

I might try jacking it up at the weekend and seeing if I can work the caliper free a bit. Ideally I'd get both rears totally rebuilt just to be on the safe side. I did even toy with the idea of buying two brand new front BX calipers (they're not expensive) and getting them sent up to bigrred for rebuilding with DOT4 seals. Then it would just be changing over locally for the bigger carriers from the GTA.

Ho hum.

Yep wrong one. A610 kit. Bigrred supplying me a GTA one as a replacement and the A610 one will go back via eBay returns...

I might try jacking it up at the weekend and seeing if I can work the caliper free a bit.

Hi Darren ........ I did not know you had already changed the sliders.
When I freed off one of mine, whilst sliding the caliper back and forth, there was a distinctive "high spot" or ridge which the caliper would often stick on and I would have to apply a bit more pressure to release it. Having squirted the silicone grease into the bellows space, and worked it again, it got to a stage where it was not sticking ..... the "high spot" had not disappeared, but with the grease, it seemed to slide over that spot. This clearly is not a cure, but it seems that these sliders can get dry and not slide easily. Even the one I was not having trouble with, after the silicone grease treatment, it slid with much less friction than before.
I have not replaced the lumpy slider yet, as I have just got them, but I did do Macon with the treated sliders with no problems at all .... even now, the caliper is still not sticking.
I am going to replace the lumpy slider with new ones, but I am also going to lubricate the sliders on the other caliper.
What this says to me is that these sliders do need to be kept greased as I suspect they dry out over time due to the constant heat from breaking.
John

Hi John.

You might well be right re greasing the sliders, however this was done when they were fitted so I'd doubt it would stick so quickly. Seems churlish not to at least have piston and seals ready should they be needed when the garage takes a loom though. Hopefully new kit will arrive tomorrow or Thurs and I can get it booked in for a look at the caliper and they can replace the piston (and re-lube the sliders) if need be.

Essentially if it's being taken off then makes sense to spend a little more time and fix it properly. It can then be re-MOTd. Good news is that other than the caliper I don't think it even got a single advisory - which is great considering how fussy they are round here.

The rear brake calliper handbrake is a a week point on the gta and 610 it is very hard to now get them to work to a standard that the Mot centres will except, John is on the money re the calliper sliders they are in my experience with mine the main course of sticking rear brakes, if that does not fix it the problems you can see were on my post Gta brake callipers, the pictures show the handbrake seals at the rear and the piston seals all created corrosion and then seizing.

Yes I read your post with interest. We'll see I guess once I've got the bits. Full rebuild is the ideal but as you and Simon found, the handbrake cables can complicate matters.

[mettersl]

My experience is that friction in the brake cables prevents the levers going back properly that then prevents the handbrake adjusters setting and that stops the handbrake working. I'm sure weak spring washers in the calipers can also contribute.
The poor availability of new handbrake cables is an issue.
The ones I got from SA for the GTA were definitely new old stock renault items and expensive. They were also two different sources/versions, one clearly a cost reduced version of the other. Is there another source?
No idea about 610 cable availability at present- that did work fine on my 610 before it came apart.

I have a pair of rear calipers available.
Both were working fine, calipers and handbrake when taken off the car.
However one of them has a broken nipple and both have good handbrake cables stuck in them.
They have both been sat on the bench for 6-8 years waiting on increased enthusiasm/perseverance to get them sorted.
I purchased replacements from Brakes International a long time ago, probably 6-8 years ago, and still have the return boxes too, worth £60 rebate.
If you or anyone else wants the 2 calipers and handbrake cables, and returns paperwork, they are yours for £150 plus shipping.
You will need to sort the broken nipple, or bleed them off the hub via the brake hose connection.BTW, I am going to Birmingham tonight if that suits any one.

I only use the handbrake once a year, at MOT time.

Well Biggred have had the calipers for over 3 weeks now, finally 'in the queue waiting to be tested' but then they said that on Friday.

Hoping the garage won't be too upset with me as they will have had the car immobile in their workshops for a month by the time they get shipped back.

Its well known that the GTA rear callipers are similar to Citroen BX. The main difference being the seals, as Citroen use the LHM fluid for both the suspension & the brakes.

I had real; problems with one of my rear brakes overheating & sticking on. I rebuilt the calliper, fitted a new handbrake cable & new slides. I was about to give up when I came across new BX calliper pistons on eBay. Not much money so I bought one. It fitted perfectly with the GTA seals from Bigg Red. I reassembled & adjusted the handbrake cable to be a little slacker than previously, but ok to hold the car on a reasonable hill. RESULT ! no more problems. I think the pistons get butchered when they are wound back in during pad changes, plus they corrode.

Ill see if I can dig out the link if you are interested.

Yes BX but with Mercedes carriers. I had suggested that to the guys at Biggred but main issue has been a broken bleed nipple and just lack of speed. Ho hum just waiting.

If I did it again I'd source a BX set and try to get the handbrake levers changed. There are more internal seals that are LHM fluid that need swapping that aren't in the kits. Shame no-one can build them up from scratch again as they wouldn't be expensive to do.

Just spoke to Biggred. Caliper has failed the pressure test on the helicoil they fitted in place of the snapped bleed screw so basically the core is scrap.

They're sourcing a second-hand core from a BX and will then rebuild using the carrier and handbrake lever from mine.

Just preparing mine for it's MOT and carrying out the usual procedure , winding back the pistons and resetting the handbrake etc..

Notice the caliper didnt appear to slide very feely, so I decided to undo both slider bolts, remove sliders, clean, re lube and attach the caliper.

When I torque up the slider bolts to 17 Nn then the caliper does not slide freely at all; very notchy. Backing both bolts off to finger tight, allows it slide freely.

If the slider bolts are securing the sliders to the caliper bracket and then the caliper slides over these slider tubes, then why does everything tighten up too much when the bolts are tightened ??