Rear brake caliper overhaul

[Mighty306]

Just started to recon a pair of rear calipers.  Have partially dismantled them and given them a bit of a degrease, revealing a fair amount of corrosion.  Any advice on the best way to clean up the aluminium alloy body?  Have read conflicting stuff on t'interweb!

For anyone else looking to refurb calipers Big Red have 30% off many of their kits at the moment.

[Stef205]

caliper bodies i normally send to the blasters.
Pistons i use some emery tape.

[Mighty306]

It's been a while, but these have come back from the blasters.  Very happy with the way they look.  Shouldn't take long to rebuild them.  Have new pistons, sliders & all the seals.

Am going to paint the carriers for sure but just wondering about painting the calliper bodies as well?  Also, any suggestions on best colour to go with a diablo red 306?  Was thinking white.

   

[welshpug]

no paint.

[Piggy]

I use silver hammerite hammered effect usually, in the spray can. Then just colour the pad carrier section as to whatever is required.

[JTaylor2005]

They look brilliant! I'm going to get my self a rear left caliper now and get both my spares refurbished

[Mighty306]

It isn't too expensive either. £20 per caliper for blasting n another £20 each for new pistons, seals n sliders. You will need to make a tool to compress the sprung washers that are part of the handbrake mechanism tho.

If you compare the cost of buying a refurbished calliper (£80 upwards) it's worth having a go yourself.

[JTaylor2005]

Nice one! Will get my self a second spare and start getting to work!

[Mighty306]

"Shouldn't take long to rebuild them"

Wishing I hadn't said this.  They're tricky little b*****ds to put back together.  Getting the teardrop-shaped key lined up as you slide the lever arm in requires a LOT of patience.

After dedicating a fair few hours at it I'm still not done.  I've managed to get the internals out of one of the old pistons but can't get the spring back in to place - it has a serious amount of tension on it.  Any advice much appreciated.

Cheers guys.

[Piggy]

Yeah they are tricky.

Got to be honest... In future I will wait for a big sale and just buy refurbed ones. For the hours of effort plus parts...

[Mighty306]

I think I might have hatched a plan to get the spring back in, involving a vice and a socket that it the perfect size.  That'll have to wait for another day tho.  My reserves of patience need topping up first!

[dsm482]

hahah) ran out of patience , better leave it for another day.. u need to compress the spring somehow to safely put them back together.

[pug306driver]

Nice, do you have an exploded view of the caliper to show parts positions etc., also a picture of the parts when the caliper is apart, forewarned and all that.

Could you also show a picture of the other side of the caliper, the pads side please mate.

[Mighty306]

It was pretty well covered by 'rikky' in this previous thread a few years back ... a reminder that we all stand on the shoulders of others.  https://www.306oc.co.uk/forum/archive/in...26295.html

I've taken some pics tho and will try to clarify a few things.  This is the order that all of the parts of the handbrake mechanism fit together .....

   

If you get new pistons they won't have any internals, which attach the piston to the rest of the handbrake mechanism.  I don't yet have any advice on the best way to get the spring back to hold the piston internals in place.

   

   

Before assembly, fit new o-ring seals from kit.

   

When putting the shaft with the threaded end back in to the caliper body, make sure the side that doesn't stick up so far faces towards the sliders.  The fatter side of the key sits on the end of the shaft.  The lever arm has a groove/slot machined in to it that mates with the top of the key.

   

A closer look at the sprung washers that will need to be compressed to get the lever arm back through and on to its bushes.  IMPORTANT - You need to insert the lever arm in to the rubber boot and turn the boot inside out before sliding it through the bushes.  (The boot can't be put on after the mechanism has been put together).

   

The tool you will have made to compress the washers will obscure your view of the key when you insert the lever arm.  That's the really tricky bit.  Make sure the key is centred before releasing compression on the sprung washers.

When putting the sliders back in pay attention to orientate them correctly (the ends aren't symmetrical)

   

Pack the handbrake mechanism with grease (I used lithium grease) before pulling the protective rubber boot over and securing with a zip tie.

[pug306driver]

Thanks, forewarned now. Some special tools needed by the looks of things. A joy to come but not yet thankfully.

For the very strong spring inside the piston, the clip that holds the internals inside the piston, a purpose made "tube" that will allow the spring to compress via the "piston internal taper", and a clamp affair ( g clamp ?? ) to straddle the piston ( suitably protected ) to push the very strong spring into/over the taper and then the spring into its recess ??

Don't know the function of the "coil" spring yet, l the one over the piston assembly on the left. How is that held together, v ia a "screw or bolt" . I can see the "tang" that fits into a slot inside the piston ? ,  to allow the piston to be rotated when unadjusting for new pads to fit ??

Is the coil spring a friction brake to stop the system from unadjusting all by itsself when the system is working on the car ????






The conical washers, perhaps using the bolt holes for the "caliper iron cross bar" , a clamp affair that straddles the handbrake shaft with feet to clear etc, which push via this special "g clamp affair" and compress the conical washers ??? 

If my memory is correct, it was some years ago now, will the outer handbake rubber "boot" slide over the mechanism ????

As I have said, I have yet to do this job so may be completely wrong.

Saw your comment with socket and vice, good call and take your time.

Off to look at rikky's thread on this subject.

Thanks Rikky.

Yeap there you go, looks a bit doddgy and I didn't realise that that other spring was involved, but it works. Now I must learn how to paste pictures where I want them !!!!

Did I say that this is a brilliant forum

[Uberderv]

I've recently bought a repair kit and I'm not too happy with the machining on the piston, rubber parts seem ok though ...

[Mighty306]

Cheers Pug306driver ...seems you found some useful workshop procedures. Confirms I'm on the right track to fix the internals back in. I can only guess that you're right about the spring wound round the internals - somehow allows the piston to advance as pads wear but stops it retracting again, until it's physically wound back in - clever!

I think it would be difficult to fit the boot after the handbrake mechanism had been assembled. Can't say it's impossible tho as didn't try.

---

I've recently bought a repair kit and I'm not too happy with the machining on the piston, rubber parts seem ok though ...

That's a shame. Tbh, my old pistons were in much better shape than expected so I probably could have got away with re-using them. The kit with the new ones came from BiggRed - seem fine to me

I'll hang on to the old pistons in case they're useful to anyone in the future.

[pug306driver]

At some point I will have this job to do, so pictures etc. are all good info for when the time comes.

Still going round in circles with central locking and engine non starting, 2 days ago when the ignition was turned on the speedo and tacho needles shot round to full speed, must be water getting into electrics somewhere. Car will lock via rf key fob but not unlock, and dead lock seems still engaged so cant open doors from the inside ? Key fob had new battery fitted xmas time.

Who knows how to disconnect the immobiliser from the engine ecu so engine will start and run please, please PM me with the info please please please.

[Mighty306]

Had a busy few weeks so first chance yesterday to have a crack at getting the springs back in the caliper pistons.  In short, using a socket to force the spring back in does work.  I used a socket of the perfect size to fit inside the piston, but this isn't quite wide enough to get the spring started on its journey.  I had to get everything lined up just right with slight pressure on the spring and then gently press the ends of the spring in, hoping they'd stay there while getting a bit more compression on the socket.  An extra pair of hands would have been a big help.  Either that or it has since occurred to me a jubilee clip of the right size could be used to squash the spring sideways while compressing it in to the piston (a bit like a piston ring compression tool)

The first couple of times the spring didn't go in square.  When only one half of it locks in to the groove inside the piston it throws the washer out that sits on top of the internal mechanism.  You can't then get the rest of the spring to clip in to place and have to take it out and start again.  So, ....another job requiring plenty of patience.

Sorry for the poor quality pics, but you get the idea ....

   

   


Or ...if you need new pistons you could go down the easy route and purchase ones with internals already fitted.  https://www.ebay.co.uk/itm/REAR-Brake-Ca...SwImRYD0Mw  They use circlips to hold the internals in place ...much more sensible!