How to rebuild your calipers

[Ludicrous Speed]

Last year I pulled my front calipers to install new pads. When I did, one pad on one side was worn significantly more than the other in the same caliper. At this point I knew I had a sticky or stuck piston. I sprayed it really well with brake cleaner and pressed them all the way back in, but knew that this was just a temp fix.

So this winter I pulled the calipers off, and pulled them apart and gave em a good cleaning. Not that hard to do, and I took a few pics along the way.

This is not a difficult job, but it is extremely important that you take your time and inspect everything really closely. It is not even required that you replace the seals on the pistons, unless you have a leak, or damage one.

A friend that guided me through this has done dozens of sets of calipers and never had to replace a single seal.........

So anyway, onto the good stuff

 

[Ludicrous Speed]

I have skipped a few steps here, but if you cannot get this far without pictures and instructions, STOP NOW, this is not for you.

Here is a pic of the calipers, after you split them apart. I used an allen tool that was built into a socket. I broke them loose while still on the bike, so I did not have to put them in a vise. Notice all the crud and brake dust built up around the pistons

 

[Commuta_Busa]

just make sure the o-rings are seated properly during reassembly. Some people rush it or forget one and then have leaks.

for doin' it yourself

 

[Ludicrous Speed]

Now I take a pair of snap ring pliers (I use these new Craftsmans, they switch from inner to outer type with the flip of a lever) and insert them into the piston. Squeeze firmly and twist as you pull the piston out. It may be difficult, but they will come out. DO NOT GRAB ANY PART OF THE OUTER PISTON WITH PLIERS!!!! This will scar it up and ruin it. It will then tear the seals after you reinstall it. You HAVE to grab the inner part of the piston.

 

[Ludicrous Speed]

Shhesh, Commuta, let me get done

I then fill a small bucket with hot soapy water. I use Dawn, and a toothbrush, and some times a little fine scotchbrite. After it soaks for a bit, use the old toothbrush and scrub the heck out of everything, and you will be surprised how dirty they really are. After I get it mostly clean, I rinse it off, and then remove the seals. The outer ones come out really easy using just your finger. the inner ones though, are a lot harder, and require that you use a tool of some sort. I used a toothpick, but you can use the little dental tools as well, just be careful not to nick or cut them, cause if you do, you have to replace it.

Notice when you take the inner seals out, they have a lip on them and they have to go back in the same way.

My attempt at a cross section------------> / /_________\ \

After you get the seals out, scrub the bores really well with the toothbrush and some fresh hot soapy water.... You may need to scrape the grooves to get all the crud out of them. I used a toothpick again, since it would not scratch the aluminum.

Then do the same with the pistons. Here is probably the culprit that made my uneven pad wear

After scrubbing

 

[Ludicrous Speed]

After you are happy that they are as clean as possible, set them out to dry, or blow them out with compressed air. The compressed air is the best way, since you can blow into all the little orifices and get the water out.

Then take your caliper and reinstall the seals the way they came out. The taper should face into the bore, like a funnel. Use your fingers to do this, it make take a couple tries, and they look way to big, but they will go back in, trust me

Your caliper should look like this:

 

[Ludicrous Speed]

Notice that there are still black stains on the metal. Brake dust is corrosive, and stains the aluminum. I could have probably gotten them a little cleaner, but I was in the wife's kitchen, and was limited to what I could use, chemical wise

Now, to re-install the pistons. Either use some fresh brake fluid, or some common isprophyl alcohol. I used the alcohol, since once again, I was using the kitchen counter.

Pour some in a little bowl, and get the piston coated with it. It helps to dip your finger in it and run it around the inside of the bore to get the seals good and wet.

 

[Ludicrous Speed]

Quickly set the piston into the bore, and using MODERATE pressure, push it back in. Do not rock it, just twist it very slightly and press steady. If you have to press very hard, pull it out and check the seals to make sure they are all the way in the groove. THis is the most important part of the procedure, don't get in a rush and screw it up now!

 

[Ludicrous Speed]

Repeat this until all of the pistons are back in. Once again, I am not going into detail on how to reassemble them, as the important stuff is shown.

Just do not forget to clean the orings that are on the mating surfaces of the calipers and check the grooves for corrosion as well.

Hope this helps someone!

 

[mike1180]

Very nice, thanks!

I thought every kitchen had a container of brake fluid on the kitchen counter?
Oh well.

 

[Commuta_Busa]

:duh: sorry, I jumped the gun on your post. I saw the first post and thought that was the whole story. I should have waited to see if it was going to be step-by-step.

 

[djsin]

 

[omslaw]

Nice write-up! I did pretty much the same thing when I painted mine... Probably be doing another set sometime soon.

 

[Boyer]

Just the info I needed, thanks

 

[Ludicrous Speed]

To me, that stuff was the easy part. Ths sucky part is trying to get them bled!

 

[omslaw]

To me, that stuff was the easy part. Ths sucky part is trying to get them bled!

Mityvac!

 

[Ludicrous Speed]

I tried one one time and it did not help much. Maybe I was doing it wrong......

???

 

[omslaw]

What I found is that air was seeping in from the threads on the bleeder screws. I pulled them out and put a bit of disc brake grease on the threads...then reinstalled 'em. That sealed up the air leak and I was able to get everything bled...

 

[wht_scorpion]

I went with speed bleeders going to need. Fast and easy to bleed brake system. One turn pump the brake lever and he comes the air. No opening and close just leave them open then when all the air is gone and fluid coming out close the speed bleeders

 

[BlueHaya]

Good write up