Repair rear brake caliper

[Phil_H]

[quote=Drumtochty]

@Phil H

@Drumtochty

The main problem I have here is that you buy all the bits and you then strip the caliper and find the bores are scrap and you have to but a recon caliper. The bits will cost between £35 and £50 depending what is worn.

I would only buy all the parts if I had stipped the caliper first to check its condition.

On the other hand if the caliper has done say 120,000 miles, I would buy a remanufactured caliper from a trusted source at £90ish.

Personally I think it most unlikely that the bore would be a problem, as it has no effect on the sealing of the system. The piston and the seals are what do the work, with the bore just acting as a guide (unlike a bore in an engine that is a sealing surface for the piston rings) and not much goes wrong with a casting.

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Nonsence Phil H.

If the bores do not come into it what do the pistons and seals then seal against, I assume you have found another magic surface there.

Please advise what exactly comes into play the sealing of the caliper.

I have rebuilt many calipers and find after say rebuilding say 10 or 15 calipers, when I had got near to doing a competent job rebuilding the units, there were still times when new seals started leaking after two or three months.

I have also had new pistons rusting and damaging bores from what I can only assume is poor quality seals or even with me clearing an area to have a clean area to rebuild the calipers that either some grit got in there as I do not have shot blasting kit properly clean the calipers, nor the skill to properly hone the bores or the measuring devices to check bore condition.

I look forward to be enlightened on what surface other than the pistons and seals are key to getting a hydraulic seal on the caliper. As every day is a school day!

 

Ok maybe I am wrong then and am always happy to be corrected, but as far as I am aware, the bore is simply a housing for the piston and a guide that holds the piston square and provided it is not severely corroded or distorted then it would have no detrimental effect to the sealing of the system as the piston does not seal against the bore (that would be metal to metal). The hydraulic seal is made between the piston and rubber seal located in the bore (which you seem to agree with in the last line of your reply), with the dust cover seal offering dirt protection. I too have refurbed my own calipers. Maybe we are just getting our wires crossed in the text. regards, Phil.

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[safetymatch]

Having spent two years striping, cleaning (removing rust from sealing faces), polishing and resealing any and all types of hydraulics,i can tell you a seal has two sealing faces, the inner and outer bores must be clean and rust/debris free where the seal sits, and the moving piston or cylinder needs to be clean or it will leak.