Brake callipers - splitting

[RiceBurner]

Just spoken with a Parts person at a BMW dealer, about TOKICO callipers on BMW bikes (the EVO system on R1150 series bikes).

I recently replaced the calliper seals on the callipers, by the usual method of splitting them, cleaning out and re-assembling. Since then I have been unable to bleed the system effectively (it's not ABS), and I'm normally pretty good at bleeding brakes.

BUT I have been told that splitting the callipers is a Bad Thing (tm) and the brakes will never seal properly again. (It should be added that BMW don't supply the calliper body seals so I had to re-use the originals.) Apparantly in order to replace the seals you have to grub around within the gap (which makes cleaning out the corroded seal chambers virtually impossible - or buy new callipers. )

Thing is - I did exactly the same job on my ZXR400 a few years ago - it wears Tokico callipers which are virtually identical to those on the BMW EVO system - and the job was utterly successful. (I was supplied the correctly calliper body seals that time, it should be added).

Has anyone else replaced the seals on the TOKICO BMW brakes, if so, how did you do it? Were you successful and did you split the callipers?

[scotty]

Hi Riceburner

I'm just shaping up to do a overhall of the front calipers on mine which is a 99 model so runs the Brembo units. I called Motorworks to order a few bits and was speaking to Darren who also has a s and he was saying the same thing ie the calipers should not be split. He was saying that if they are split there is only a 50% chance of getting the calipers to work properly. You will definitely need to replace the small o ring seals from another source as BMW don't sell these and it may be better if you smear a small amount of vaseline on the flat mating surfaces of the calipers as they come together. This may help seal the system. BMW do not sell the piston seals separately and only do a kit including new pistons. This is a bit of a joke so it might be worth approaching a Brembo specialist if one wants to only replace the seals. You might also want to replace the standard bleed nipples with some Speed Bleed nipples as it makes bleeding the system a lot easier.

[RiceBurner]

Hi Riceburner

I'm just shaping up to do a overhall of the front calipers on mine which is a 99 model so runs the Brembo units. I called Motorworks to order a few bits and was speaking to Darren who also has a s and he was saying the same thing ie the calipers should not be split. He was saying that if they are split there is only a 50% chance of getting the calipers to work properly. You will definitely need to replace the small o ring seals from another source as BMW don't sell these and it may be better if you smear a small amount of vaseline on the flat mating surfaces of the calipers as they come together. This may help seal the system. BMW do not sell the piston seals separately and only do a kit including new pistons. This is a bit of a joke so it might be worth approaching a Brembo specialist if one wants to only replace the seals. You might also want to replace the standard bleed nipples with some Speed Bleed nipples as it makes bleeding the system a lot easier.

hmmm - cheers scotty. I wonder why everyone's so scared of splitting the callipers?? 5 years ago it wasn't an issue at all....

I wonder where I can get Tokico seals from....

[r550s]

have split & rebuilt the BMW branded calipers with no problem - maybe that was luck though! Used a standard viton o-ring between the halves. The factory manual doesn't state the torque for the bolts that hold the halves together - I marked one before i took it out, cleaned it & oiled it, and it took 37 Nm to get the mark to line back up, so that's what I rebuilt them to. Maybe overtightening is the problem - it's easy to 'pull' the thread up in the aluminium body & make a raised dome of a couple of thou around the threaded hole - once you've done this, it'll never seal, and extra tightening only makes it worse. The calper halves will no longer be rigid either. If I sound like somebody who's made this mistake in the past , well, yep!

[throttlemeister]

The service manual specifically states to not pull them apart. And to service and clean them, you do not need to. Though admittingly it would make life easier.

[winger]

Splitting calipers tricky shit!! your into the realms of more luck than judgement.

[Jason M]

I split mine on the S last year - put new BMW pistons and seals in. Did it on my knees on a dirty floor in fact. I hate bleeding brakes and it took a few goes but once I'd bought a 40 quid vacuum jobbie it helped shed loads. Having said that it took about a week to get them bled properly about a month ago when I undid one of the banjo bolts. The brakes are really good now though

Jason

[scotty]

I'm just about to completely overhaul the front two calipers and this post has got me worried. Like Riceburner I was going to split the things and remove all four pistons to clean up the bores properly. I even bought a piston removal kit specifically for this purpose. If it's not recommended to split them then how the blazes can you remove all the pistons knowing that at least a couple of them are going to be stuck in their bores. Leaving the calipers intact it's possible to pop one out at a time but you can't clean the bores properly with all the brake fluid about and there is no real working room to clean the bores up properly. It's a complete joke. Has anyone approached a Brembo specialist to get their take on the issue ? Maybe they can provide the correct seal and advise on how the things can be resealed correctly. They are designed to be split so surely there must be a correct way to do it.

[Archie]

I think it's all a big fuss over nothing really. The only way to clean a caliper proprely is to split it. (Unless it's one of the new monoblocs and then you are knackered.)

The only problem I've had is that Brembo have supplied an o-ring that's too thin for the caliper join, and weeped fluid. This is the o-ring that seals the two caliper halves and is about 10mm dia. I had to find thicker o-rings, as the ones supplied in the kits were visibly thinner than the ones that came out.

This has happened on both early 1100S calipers and Ducati 1980s Brembos.

Other than that it's not rocket science really.

[throttlemeister]

You can blow them out with ease 2 at a time with compressed air.

[scotty]

Archie

I agree they should be split no problem. I'm just dotting all the i's and crossing all the t's before I start this job. There must be a correct procedure in doing this job as the calipers were originally built this way.

It sounds like you approached a Brembo specialist and they gave you the wrong seals. Getting the right seal is probably the hardest task in all this as if the wrong one is fitted and the things don't bleed properly then it's all got to come apart again. Would really appreciate knowing what seal size did eventually do the job correctly.

I'm trying to get everything learnt befor I start this task. I intend to scrap the original front brake pipes and replace with a simpler stainless 2 line unit of 1 line directly to each caliper. The old bleed nipples are also coming out to be replaced by 303 stainless steel speed bleeders. After doing all this it would be sod's law if I can't get the brakes to bleed properly on account of a wrong 10p seal.

[RiceBurner]

I'm just about to completely overhaul the front two calipers and this post has got me worried. Like Riceburner I was going to split the things and remove all four pistons to clean up the bores properly. I even bought a piston removal kit specifically for this purpose. If it's not recommended to split them then how the blazes can you remove all the pistons knowing that at least a couple of them are going to be stuck in their bores. Leaving the calipers intact it's possible to pop one out at a time but you can't clean the bores properly with all the brake fluid about and there is no real working room to clean the bores up properly. It's a complete joke. Has anyone approached a Brembo specialist to get their take on the issue ? Maybe they can provide the correct seal and advise on how the things can be resealed correctly. They are designed to be split so surely there must be a correct way to do it.

Mine are Tokico's - but I share your thoughts exactly.

[RiceBurner]

You can blow them out with ease 2 at a time with compressed air.

How much is a compresser that'll shift a really stuck piston?

[throttlemeister]

Mine were stuck to the point I could not move them by hand. They were blown out before I had full pressure on. They blow out really easy with air.

[Blackal]

Mine were stuck to the point I could not move them by hand. They were blown out before I had full pressure on. They blow out really easy with air.

Why not just couple them back up to the brake master cylinder and use hydraulic pressure to shift them?

Hydraulic power is a lot safer than coupling up an air hose.

Using compressed air is a bit "Yee-Hah" in comparison

Al