Sunday strip down! Rear brake

[zYgoat]

Hey all!

So I spoke to Rick O on friday night about my rear brake issue and my ride height and did the following today after i got back from camping.

I struggled for a while to removed the caliper because the disc is so badly worn it actually has a lip on the outer edge. After first taking out the retaining pin it eventually came out




Didn't really know what i was looking for at first... but i got to work cleaning everything as well as i could.
I found that the below-marked drainage holes were completely blocked up and i'm sure that was contributing to build up of crap in the caliper.


Cleaned it all out and then started to inspect the pistons.

Whilst pumping out the pistons(via the rear brake) i noticed that the pot nearest the fluid inlet was coming out a lot faster than the other(nearest the bleed nipple)... is that normal? If not, is that piston likely to be seized?

After that i was fiddling with the slider and read in the haynes manual that the slider should slide "freely." Mine, did not. After much pushing and pulling and head scratching, it popped out and this is what i found...

In the image i'd cleaned the slider up a bit and found those burrs on the pins... is that normal?


Greased up all parts with red silicone grease and reassembled...


Now, when it came back to pushing the pistons back before installing pads... it was VERY hard to do. I had to(using a pieace of wood) sqeeze them back in with everything i had, and even then... it seemed like the rear piston(the one that didn't move as much) wouldn't go all the way back in

Needless to say that i struggled to get the whole thing back onto the disc and bike, but now... even if the one pot is seized, it's still A LOT better than it was.
I can now at least push on the pedal and NOT roll the bike back and forth. Still not as good as i'd like, but it'll do until i can completely redo the brake and replace the disc.

It could still have done with some more cleaning, but it was threatening to rain most of the day and i was suffering with last nights consequences

Other work i did, was to replace a blown temp gauge light(1.7w) and to adjust the preload on the shock to take up plenty of sag. Feels much better now... must have tightened the spring by about 12mm.
Ideally i want to by a new shock with adjustable ride hight... but i need to move and then get my finances in order:)

Thanks again Rick for all your help and advice!

Cheers all!

[ibby4585]

Good start mate. I doubt you will get the back brake better without at least getting a new disc and replacing the fluid and bleeding it correctly. Might be worth checking your rear brake hose too. It's probably 20 years old too. Go for a braided replacement when you do it all properly.

Kris

[zYgoat]

Cheers thanks Kris!

Yup, will do... new disc, new seals and a complete bleed. Was also thinking of the braided lines :D

Any possible MC upgrades? I'd like then to be sharper in general and have so much travel in the lever?

Wes

[ibby4585]

No just keep the m/c it's fine. You dont want the rear brake too sharp. The pistons seem fine in your caliper, personally I would pop them out give them a good clean, look at the seals they be fine so just push the pistons back in and work them in and out so they move easily.

Remember the top seal is a dust seal the inner is the main seal to check.

[amorti]

There is so much gunk on that, I think you are over oiling your chain. Not a problem for your chain but gets your bike filthy and on a SSSA bike the back brake collects a lot of it and gets contaminated with grease, then it won't work properly.

IMHO you are going to have to do the job again. Clean the caliper body more thoroughly using a brass brush, pop both pistons out and remove the seals, I suspect the dust seal on your seized pot is no good. Dig out the seal grooves using a dremel wire brush attachment of toothbrush-sized brass brush (Wilkinsons or most £1 shops). Then refit new seals lubed with red grease. Do that lot and your brake will work much better.

The excess lever travel might be being caused in part by the state of your caliper.

Here is the rear caliper from my old Daytona that you could use as a template for 'how clean is clean enough'

[Cammo]

Got to agree with amorti, that whole rear brake looks cactus zygoat!

[zYgoat]

Thanks guys :)

I agree... the toothbrush that i was using wasn't doing anything! I'll get some of those brass brushes and redo it.
I'll also order up some new seals.

So just to clear it up... are the pistons supposed to come out at the same time when i pump the brakes?

Cheers

[dgunthor]

yes, should come out at a similar rate

[amorti]

Thanks guys :)

I agree... the toothbrush that i was using wasn't doing anything! I'll get some of those brass brushes and redo it.
I'll also order up some new seals.

So just to clear it up... are the pistons supposed to come out at the same time when i pump the brakes?

Cheers

They'll never come out 100% symmetrically as there will always be a slight variance, but it should definitely be pretty close. You should always be able to push pistons back in just with thumb pressure.