knackered brake seals - how much?

I'm just doing the brakes on mine and my son's SVs - filling and bleeding the front brakes is not difficult at all, neither is replacing the seals. The most finicky bit is getting all the crap out of the outer seal grooves. Make sure you do that thouroughly or the outer seals might start pinching between the piston and bore.

Seals were about £13 per caliper if I remeber right.

I tried getting a small tube of red rubber grease but I could only find it in 500g tubs. As I now have loads PM me your address and I'll send you enough to do your brakes for nowt (if you still want to DIY that is.

Cheers Keith

Originally Posted by BigApe

The rubber grease IS critical...

It is? Whoops.

Can't say I've had any problems with it's absence though, is it just there to stop the seals wearing?

[TSM]

Originally Posted by Flamin_Squirrel

It is? Whoops.

Can't say I've had any problems with it's absence though, is it just there to stop the seals wearing?

Neither have i, mine are a K3 set of fronts that i have done 10000miles on. When putting the seals back in i just dipped them in a bit brake fluid. They were out again just a few weeks ago and looked completley fine, i have also not had any fluid loss at all.

It is there to keep the seals seated in position and allows the piston to slide back and fore freely. The lack of the grease means that the seals can stick to the piston and can be pulled out of position. That in itself will cause the pistons to stick. Result being brake binding or ineffective brakes.

Worse case would be fluid leakage.

Thanks for all the input chaps.

I've checked the inner seals and they are fine so I only need 2 dust seals. I'm going to give it a go myself as it sounds easy enough. It was definately a case of the dust seals binding to the pistons and then coming out of place and hence allowing more and more salt and, well, dust really, into the calipers and binding the whole thing up.

I managed to empty all but a few mm of the brake fluid so I'll need to bleed it all out (the fluid has been in there for nearly 2 years now!). While I'm at it, I'm going to get the right-hand side pistons out and clean them up too. Do you think that's a good idea? Is it possible to take the pistons out gently and use the same dust seals again on that side? I could do without the expense of another 2 seals! Also, any tips on getting the pistons out? Cause there's no fluid in the system, they are only protruding about 1cm from the caliper body. Can I wrigle them out with vice-grips and some material to stop scratches?

Unless the seals got damaged when they came out, there is really no need to replace them. Give them a good clean and inspect them for deterioration. If they look good stick them back in.

Thanks Ape.

Now just need to convince the Mrs that fixing the brakes myself is NOT dangerous!

Ain't it typical, January 3rd, dry, sunny, mild, the roads are dead and the bike it out of comission!

Originally Posted by Dirty Baz

Ain't it typical, January 3rd, dry, sunny, mild, the roads are dead and the bike it out of comission!

DRY I went out for a ride with my brother and managed to get soaked to the skin. Did have a bloody good time though.

Hello Baz,
I just changed the front brake piston seals at the weekend.
While it is still fresh in my mind, here are some tips that might help.

I know you have already drained the fluid, so 1st option is to try to blow out the pistons using compressed air at your local garage. If you had a helper I would say use them as I found trying to juggle holding the air hose & hold the nozzle tight onto the fluid intake on the caliper a bit difficult.
1st remove the pads and insert a piece of wood in front of the pistons that will allow the piston to come most of the way out. Now try to get a good press between the air nozzle and the fluid intake and send some air in. If you are lucky, both pistons will come out as far as the piece of wood.

I didn't actually use a piece of wood, instead I use the compressed air to blow out one piston, then re-inserted the piston to just sit into the seal(piston seal, not the dust seal) and held it there with a small clamp. This allows the compressed air to work on the other piston. I would guess a piece of wood might work better if the thickness was just right to allow the pistons to come out as far as possible with losing the seal. Then in order to get the pistons out the last little bit, I used a screwdriver with a handle that fitted snugly into the inside of the piston and a bit of wiggle & pull got them out.
The screwdriver handle was also useful to help refit the pistons - you need to be able to push fairly hard & straight to get them to pop back into the cylinders.

Above was fine until 1 piston refused to budge using compressed air. The only way I could think to sort it was to complete the seals on the caliper where I had got both pistons out, re-fit pads, etc & re-fit the whole caliper.
Then I had re-fit the other caliper to the brake line, re-fit the piston that had come out & clamp it in place. Then I had to refill with fluid & bleed in order to get to the point where I could pump the brakes until all the hydraulic forces were working against the stuck piston - this worked ok but it was a pain to have to refit almost all components, fill & bleed.

In hindsight, what I think would have been best would be to:
* Don't disconnect the brake lines - just loosen & quickly re-tighten enough to get a decent seal.(This allows you to loosen off the brake line at the end as the caliper will be dangling loose and not so easy to loosen a tight nut)
* Remove both calipers
* Remove both sets of pads
* Insert a piece of wood in each caliper to allow pistons enough space to come out without losing the seal(if this happens, the fluid will rapidly drain and won't be able to exert pressure on the other pistons.
* Remove wood pieces when all 4 pistons have extended out.
* Disconnect from brake hose.
* Insert screwdriver handle(that is a snug fit) into inside of piston and wiggle & pull!

To be honest, if you have not already removed the calipers, you might be better off to refill & bleed, and try to get all 4 pistons pushed out as far as possible using the hydraulics.

Good Luck!
George

Originally Posted by SVGeorge

To be honest, if you have not already removed the calipers, you might be better off to refill & bleed, and try to get all 4 pistons pushed out as far as possible using the hydraulics.

That's the way I do it. I unbolt the callipers from the bike and then use the hydraulics to pump the pistons out as far as the oil seal. I then disconnect the lines, drain the callipers and take them inside to do the rest in front of the tv.

As for fitting them back in, I have found no problems with just pushing the pistons back in by hand.