refurbing rear calipers

[Dean.s]

I've finished the front calipers and now i need to refurb the rears.

My haynes book says not to do it & refers you back to a dealer.

Has anyone refurbed their own and have any tips for a successful job?

My main concern is the hand brake mechanism, i really don't want to damage (or touch) that.

The front pistons i popped out with compressed air but i'm not this will work on the rears.

[LMR]

Dean

There are plenty of guides on the internet. I bottled it and got a specialist to do mine

[Dean.s]

I'd searched and viewed a couple but a diyer hands on feedback is what i'm looking for as i may also give them to a pro if it's too iffy to do myself.

[Mr Pharmacist]

I did mine - took them completely apart and re-assembled them. It was quite straightforward - I think the only issue I had was finding some of the metal plugs to replace the originals I took out.

[jonat127]

I did mine ok.
Didn't bother to take the handbrake mechanism out as it can be greased in situ and that is all that's needed.
I did find the O rings supplied from mittelmotor were too fat. Couldn't make them fit at all. Luckily I have a big box full of O rings so I just found some that fitted better.

[davep]

I am doing a few sets right now. Fortunately I have 40 years experience with the damn things. In the old days there were no seal sets for them. Today it is very hard to get replacements for the inner and outer adjusters.
To access the rear adjuster, you need to remove the cap It is best to use some tool to allow you to hit the cap directly with a hammer; this will help to release the cap. Be careful not to damage the copper ring under the cap. The outer adjuster is secured with a 13mm nut, and the circlip helps keep it from getting lost; always loosen the nut before trying to turn the adjuster. It is very bad news if the Allen key recess is damaged and/or the adjuster will not turn freely; it is time to turn over to a pro.
If the adjusters are not damaged and the rear cap can be removed readily, then there is a good chance you can DIY. The outer adjuster must rotate counterclockwise to push the piston out. The inner adjuster works in reverse due to the extra gear involved.
I remove the pistons one at a time. I remove the square section rings in the bore, then clean the bore thoroughly. The portion of the bore outside of the seal ring is critical since it is usually the culprit when the piston does not move freely. I use dental tools and Q-tips to clean the seal ring groove and the rest of the bore. Do not use lubricants inside the bore that are not compatible with brake fluid; most brake lubes are for external use ONLY. I clean the pistons with green scrubbies; brass brush may be okay, but steel brushes can cause scratches. Pistons with significant pitting are probably not useful; a little pitting on the outer 4mm will likely not damage the new seal. I always replace the inner and outer O-rings on the adjusters, but I have the tools to do so. A good idea to replace the bleed nipples with new 7mm parts; do not chase the threads in the castings with taps since this can make the nipples too loose afterwards.

[Dean.s]

All good advice, thanks, it's what i was looking for.

[Green Ernie]

I had mine refurbed at Bigg Red in Worcester. One of the back calipers leaked and they had put the handbrake springs back on the wrong calipers (ie left on right etc). They took about four time as long as quoted, couldn't find one of the calipers when I originally went to collect them so I had to spend a few hours wandering around Worcester while they found and finished off the one caliper. The customer service was poor but the brakes work fine. Check out the PMB website, I think they have a how to diy video on there.

[Dean.s]

I bought my seal kits from big red. I've used them for years without a hiccup but everyone can have an off day.

[Dean.s]

I started on the rears today. Didn't go too well. I can't get the piston to wind back onto the the adjuster shaft for the handbrake adjustment!

[Nicktune]

does anyone know the size of the rear calliper pistons I'm fitting some modern day callipers to mine probably Audi s3 r36 golf etc. but want to complete piston sizes and I've already sold my old callipers

[Nicktune]

does anyone know the size of the rear calliper pistons I'm fitting some modern day callipers to mine probably Audi s3 r36 golf etc. but want to complete piston sizes and I've already sold my old callipers

[Dean.s]

Lost my cool today so stayed away from the calipers and emailed PMB for parts/advice.

I'll measure the complete caliper when I next go to the garage.

[davep]

Rear 914/4 caliper pistons are 33mm.

[Dean.s]

It looks like the adjuster has lost the thread on the end hence why the piston won't screw on. Anyone know the thread size for the adjuster on the handbrake side?

Failiing that what other caliper can be used instead? 4 bolt hub on a 74.