Rebuilding Brake Calipers - Cleaning Bores & Pistons

[willg]

Hi RR,

I'm currently rebuilding the front brakes on my rx7, they have been sitting for years and years, off the car. I managed to get all of the pistons out (took heat and brute force!) but this has left me with bores and pistons that are a little rusty and cruddy. What is the best way to go about cleaning these? Fine emery cloth?

Also I was going to degrease all the caliper parts using the bilt hamber surfex hd, but its water based so I don't want it to corrode anything

[ant260z]

Looking at that first pic, i would say that 6 of the 8 pistons are beyond serviceable, so you might as well replace all 8.

Go very carefully with fine emery on the caliper bores, but if there is anything more than the faintest of scuffs/scratches from removing the old pistons or corrosion, i would replace with new.

Your life is quite literally in those components hands, don't be cheap with renovating them or buying new!

[skkylinedave]

For the time and finish i would just give them to big red and get them refurbed as new . No hassle.

[slater]

Pistons are scrap. Try looking for replacements. If you cant get them maybe consider new calipers.

The bores can be cleaned carefully with emery/wet and dry etc and finished with a flex hone. They are less critical than The pistons but you need to make sure there's nothing in the bore that's going to jam or score the piston.

[ChasR]

What's been said basically. The pistons are dead, but the calipers should be OK.

I'd also be tempted to send them off to Bigg Reg. But as Slater said, as long as nothing can jam up the caliper, it will be fine.

FWIW the kits aren't that pricey. I got a set of pistons and calipers for my W108 for £60 for the front axle. That almost makes it worth Bigg Red doing them. But it was a therapeutic exercise mind you.

My pistons were way more saveable than yours, but I still binned them. As said, it's really not worth it on a safety critical component.

[madzuki]

To clean bores, know any dental technicians? Ask for some blue cylinders or Renfert pre polishers, either cylinder or wheels. Use in a Dremel or similar at Low speed, no more than 10,000rpm.

Much better than emery cloth, wet/dry etc

[datman]

i uses a razor blade on the pistons, (bin them if any bad pits) nd a wire brush in a die grinder for the bores. A someone mentioned earlier the bores are not relied upon for a seal but need to be de rusted to allow the piston to move freely. the essential tip is to use loads of red rubber grease when reassembling, the pistons should push in with thumb pressure, but sometimes it is hard to get them started as they have to be absolutely straight.