DIY: Rear Brake Caliper Rebuild

Luke-H

Member
WORK IN PROGRESS. More will be added. Let me know if I missed something
So since there isn't any DIY on here for rebuilding rear brake calipers I thought I'd give it a shot.
Obviously this is how I did it and it might not be correct and I take no responsibility if you stuff up, etc. :)

What you're going to need:
Caliper
Rebuild Kit. MB857874 for FTO it also works for proton but the spring seal seems to be slightly too long.
MB857875 for EVO III as the piston is slightly larger requiring a different boot. All other parts are the same I believe.
Brake Cleaner
Rags
Brake Fluid
Internal Circlip pliers. Preferably the longest skinniest pliers you can find there is not a lot of room in the bore.
~19 mm pipe to press on spring case
Rear Piston Tool
2000 grit sandpaper for remove surface rust from piston and bore.
Pliers




Dissasembly
To start undo the bolt that separates the two pieces of the caliper and then pull the two pieces apart. Next remove the other pin and then remove the rubber boots.
The boots should pull off very easily. My slide bolts were rusty so I cleaned them up with a wire brush.

Next you need to remove the piston. You can buy a rear piston tool from Repco. However to wind out the piston you will have to cut most of the points off.
Wind the piston all the way out and remove it from the boot. Then pull the piston boot out of its groove and past the metal ring trying not to rip the boot.
Use a small flat blade screw driver remove the metal piston boot ring.

The next step is the tricky step and it worked better for me using two people. Get one person to push down on the spring case while the other uses the circlip pliers
to remove the circlip. The spring and spring case should just fall out. I used a piece of ~19mm reticulation pipe.




To remove the spindle get some pliers and wrap them in a rag and pull on the spindle and it should pop out along with the little guide ring.
Use some long noses pliers to remove the metal pill sitting in the auto adjust mechanism.

Now you can remove the brake return spring and the auto adjust spindle will just pull out. You might have to lever out the seal that the spindle slides through as it may be stuck.

Then use a flate blade screwdriver or a kebab scewer to remove the piston seal now there is more room in the bore.


Cleaning
Using some brake cleaner, brake fluid and rags clean the inside bore of the caliper and the piston. Then slightly wetsand the piston and bore with the 2000grit sandpaper
to remove any light surface rust. Also give the auto adjuster parts a nice soak and clean to remove and dirt.


Assembly
Get the piston seal and coat it in brake fluid. Do not wipe off the special grease that is on the seal.


Replace the return spring seal. This may not work if you have proton calipers so you may need to reuse your old seal. The metal part of my new seal was slightly longer but some gently persuasion may get it to seat. I just didn't bother because mine were in alright condition.
Now put some special grease on the new seal and fill the hole in the spindle with the special grease. Then slide the auto adjuster mechanism back into the caliper.
Making sure that spinning piece has the opening facing into the bore.

Special grease


Swap the Oring on the bottom of the spindle with the new one and fill the base with grease. Put all the pieces of the spring mechanism with the pill in the groove in the bottom.
Push the assembly into the bore until it locks in place and the holes in the plates are in the holes in the bore. Then install the spring on the adjustment mechansim


Now for the fun part. While pushing down on the spring case you need to insert the circlip back into the bore and into its little groove. This is not easy at all.
IMPORTANT: The workshop manual says to face the circlip opening towards the bleeder hole in the bore. It is written in bold with the words CAUTION so its probably important.
I you didn't align it I wouldn't worry one of mine isn't aligned. I believe you align it to decrease the risk of inertia popping out the clip but I doubt the clip will just pop out. I would still align it iff you can. Someone correct me if I'm wrong.

I used a ~19mm piece of reticulation pipe and that seemed to work. If you can get one side of the clip into its groove or the clip most of the way down the bore you should be able to use a screwdriver to finish seating the circlip.

Next get your piston tool and use it to screw the piston back in. Then install the piston boot making sure to coat the groove in the piston and the bore with the special grease
as well as the inside of the boot. Then place the boot on the piston and make sure it is inserted into the groove in the piston. Then push the outside of the boot into the bore and
use a small flat head screwdriver to push the lip of the boot into the groove. Then insert the snap ring to hold the boot making sure it is in the groove and holding the boot in place. Screwing the piston out a bit will make inserting the boot ring easier.

Screw the piston back out to check the boot is installed correctly. One of mine has some odd air pockets things when screwed out but that's not a big deal either it still seats and isn't twisted or torn.

No pictures yet for the rest but its pretty simple. Here is a simplish explanation.
Wipe the special grease on the inside and outside of the slide pin boots.
Then fill the boot/metal tube with either the special grease or copper grease/anti seize which is what I like to use for sliding pins.

Then put the pad clips back in the other piece of the caliper and insert the pads.
Screw the sliding pin and its metal boot to the other caliper piece and push it into the metal holder.
Next screw the other pin in place through the boot and the caliper will be complete.

You should end up with something like this.

Sandblasted before rebuilding then painted with two coats of Duplicolor engine primer, then two coats of Duplicolor Metalcast Ground Coat finished with three coats of Duplicolor MetalCast Red.
The MetalCast paint is awesome the caliper is a nice dark metallic red.
 

lancer1993

Active Member
They'd look better in yellow ;)

But seriously good job, how much should the kit cost?
I guess the cost to do the front and others types of calipers will be about the same?
 

Luke-H

Member
Trondabron said:
Thanks Tron

lancer1993 said:
They'd look better in yellow ;)

But seriously good job, how much should the kit cost?
I guess the cost to do the front and others types of calipers will be about the same?
I paid ~$15 per rebuild kit for the rear. So basically $30 to do both calipers.
Same with the fronts.
 

Spetz

Well-Known Member
Hey guys,
I rebuilt my rear brake calipers yesterday and these are my findings that contradict the above DIY to some extent:
1. Installing the circlip back with the needle nose pliers seems really difficult - What I did was I installed it most of the way and then wound in the piston to get the circlip to clip into the groove.
2. From the DIY post:
IMPORTANT: The workshop manual says to face the circlip opening towards the bleeder hole in the bore. It is written in bold with the words CAUTION so its probably important.
I you didn't align it I wouldn't worry one of mine isn't aligned. I believe you align it to decrease the risk of inertia popping out the clip but I doubt the clip will just pop out. I would still align it iff you can. Someone correct me if I'm wrong.

I do not see how inertia has anything to do with it, that circlip is not going anywhere.
I gave this some thought out of curiosity and came down to the conclusion that the opening of the circlip must point towards the bleeder hole such that when bleeding the brakes there is no stuck pocket of air that is not removed on the other side of the circlip. Not sure if this is right or not but it is the most logical deduction I could make.
 

pelican

Active Member
I gave this some thought out of curiosity and came down to the conclusion that the opening of the circlip must point towards the bleeder hole such that when bleeding the brakes there is no stuck pocket of air that is not removed on the other side of the circlip. Not sure if this is right or not but it is the most logical deduction I could make.

i think i agree with your reasoning, though it’s also interesting to observe that it’s easiest to get a set of circlip pliers onto it when it is oriented correctly. when clocked at other angles the caliper body can block the handles of the circlip pliers. so if nothing else, correct orientation will make the next rebuild a bit easier!

edit, forgot to ask questions:

that needle roller bearing with the window in it inside the handbrake lever mechanism... is there a trick to extracting it without destroying it? hoping to tear down completely so i can paint before rebuilding but i’ve had a feel around in there and it feels like it would need destructive force to get it out

and what’s the little rubber thing on the back side of the floating slider?

the rebuild kit has two o-rings. one of them obviously fits on the end of the piston spindle and seals the brake fluid from getting into the handbrake mechanism. the other is smaller, and i have not yet found where it goes???
 
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pelican

Active Member
oh hey looky what i found... the rear calipers on an rx7 are more or less logically identical, so these two videos are a pretty good indication of what to expect:


 
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