Splitting callipers for plating

[Andrew1967]

Never done this before but are there any pitfalls in splitting callipers for plating ?

Are there any specials seals etc ?

[Thorp]

Just the one seal between the two halves, readily available from the usual suppliers. I rebuilt mine for my Cooper during the first lockdown....

[Gary Schulz]

Do you need to mask the mating surfaces between the two sides of the caliper so you still get a good seal? Also how do you prevent the plating from getting into the cylinder bore?

Sorry Andrew, I don't mean to hijack the thread but I am going to be rebuilding calipers soon also...

[Andrew1967]

No worries Gary, feel free to post as they are all relevant questions

[GraemeC]

I don't think plating will pose a problem with the mating faces or the bores. The faces don't form a seal - that's handled by a square section o-ring and the pistons in the bores are a loose enough fit that a few microns of plating won't be an issue.

If it was paint or powder coat then it would be an issue (but also easy to mask off)

[Dearg1275]

If you want to plate them why not split them, clean and rebuild, seal everything off and then plate the completed unit. No masking required. A little plating on the external surface of your new pistons will not hurt and the dust seal should keep the plating out of the bore. If you want to be doubly sure run a bead of wax round the entry to the bore.

Never tried it.

D

[Andrew1967]

Spoke to the plater who said they are normally done in halves so will probably go with that.

Found the seals on-line. The bolts are recommended to be changed.... are they anything special - high tensile ??

[GraemeC]

All the original bolts I've come across had a 'slug' of nylon in the thread - sort of a nylock bolt. I'd assume that what they recommend changing them.
They're not torqued overly far so I can't see it being a stretch problem.

I'd personally clean and refit with a decent threadlock

[Andrew1967]

Thanks Graeme, got some good quality threadlock at work

[Spider]

If Splitting them, AP recommend replacing the Bolts and the Bridge Seal, which aren't included in a standard overhaul kit, hence why they usually recommend they not be split. Having said that, I've re-used the original bolts on many sets I've done.

I'll just express a little caution though at having them plated. Being an older casting they seldom plate well, they will likely come out patchy. There's nothing to loose from doing it, but just be prepared. You'll also want to de-gas the castings after plating, which is a simple matter of putting them in the oven at 180 - 200 for 20 minutes.

I've found on cylinders that have been plated, the rubber seals don't seal too well against the plated surface, so you'll either want to mask those places off or remove the plating after. Given the places on Calipers that the seals go, they are difficult to mask off. I remove the plating with wire wheels or brushes, some of these are boiler cleaning brushes, which look like Bottle Cleaning brushes only in wire, run them in a drill and go easy.

[Andrew1967]

Hi Chris,

The plater says callipers have to be nickel plated as they are cast and then yellow zinc plated (well that's what I think he said) and therefore more complicated than plain plating. That said, he quoted about £45 for both callipers and the servo parts, which seems reasonable.

I understand what you are saying about the seal operating surfaces and had some reservations about that point, although it's currently a 1 - 1 draw on that issue with Graeme

[Fanfaniracing]

That's what i have done a few weeks ago.

1. Push the outside e piston out first
2. split the Caliper
3. push the inside piston out tru the Brake hose hole
4. strip the Caliper entirely!
5. clean as good as possible. If blasting, then only with very low pressure and new media.
6. give them to plating to your shop of confidence
7. fit all new seals and stainless pistons.
Use ATE Brake paste. Also renew the cooper seal and new Bolts with locktite.

Voila: Your Brake Calipers are better than NEW!

[Fanfaniracing]

I think i have done 30 or so pairs like that and never had any issue

[Andrew1967]

I'll be pleased if mine end up looking like that

If the outer piston is pushed in flush, what's the best way to get it out ?

[Aginley]

I used an airline but it came out like a bullet

[Fanfaniracing]

Yeah! Be careful. I clamped my fingers once...

[MiNiKiN]

I built an adapter so I can press them out with the grease gun - messy, but not as dangerous as compressed air

[InnoCooperExport]

I've used compressed air, but always put a piece of wood in the caliper for the pistons to push out against to. Ought to stop them flying out like a bullet too.

[Andrew1967]

Luckily they were all sitting out and three were free

Managed to work them out with some WD40 and a pair of water pump pliers.

The other one was an inner one and a couple sharp taps with a punch through the hose hole with it on a piece of wood soon had the piston out.

They could probably have gone again if I just wanted to paint them up but as I have new seal kits and pistons it makes sense to do the job properly.

['S'-type]

At what point does a caliper become unsalvagable? I've got a few that have been kicking around the garage for years that I didn't get round to chucking out. I was of the understanding that it wasn't worth mucking around with old calipers especially if there was any kind of corrosion in the bores. Heard bad things about splitting them too.

Given they are readily available these days, what is the reason for refurbishing a caliper as opposed to forking out for new.
Just wondered is it cost, originality or satisfaction in completing what looks a comparatively easy process?
AP ones aren't cheap and not exactly the same in appesrance as the originals. I'm sure Minispares alternative quality are up to the job. But what about the cheaper still offerings out there? A pair for less than £100.
What are people's thoughts on this? I will be facing this decision soon as I am about to recommission brakes on a car that has stood for a long time. Calipers likely seized.