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Brake calipers

I'm in the process of overhauling the front calipers on my SDI. It's a late EFI, so has dual circuit brakes with four pot calipers and vented discs. All the pistons are rusty and will have to be replaced.

According to the workshop manual when overhauling these pistons have got to be kept with their bore. Why would this be, given that replacements are available (at a cost)?

I'm asking, because new pistons are 11 quid each from Rimmers, and no longer available from Lockheed, although seal kits are.

I bought some secondhand 4 piston calipers which can't be used as they are single circuit and for solid discs, and have stripped them down and the pistons are perfect. I'm going to use these with new seals in the original calipers and see how it goes.

Also, the single circuit calipers have one bleed nipple, the dual circuit three. Why?

Reply to
Dave Plowman
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I *think* it's because it is a PITA to get the pistons back in.

sPoNiX

Reply to
sPoNiX

This discussion came up before, it seemed that there was no real reason to keep used pistons with their original bore except it was just good engineering practice. Obviously new pistons have no matching bore, old ones will be ok if they fit !!

Three bleeds are necessary since the fluid route in the caliper will preclude having an "always going upward" route for both circuits, therefore one circuit needs to be bled at two places to avoid an airlock.

mrcheerful

Reply to
mrcheerful

I think they are just playing safe. The same was said in the Toyota w/shop manual. when I reconned a mates Celica 4 pot calipers. I checked all pistons with a micrometer. They were identical. I'd have no hesitation in putting them back in any order. There's clearance on the piston bores anyway. I can't conceive of any reason for the advice. Mike.

Reply to
Mike G

Definitely. In practise they will be fine - done this on several cars, always kept a close eye on the pistons afterwards (just in case) and never had any trouble / leaks / seizing / etc...

Reply to
DocDelete

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