2004 R1200GS Front Brake Help NEEDED!!

[NicD]

I forget which year your bike is but one thing to note is that the calipers do sometimes spit the dust seal out. On mine it was the lower inside piston. It came out much easier than the others as the dust seal had been ejected. So when i stripped the caliper there were only 7 seals! I cleaned the dust seal seat and all was good on reassembly. I don' tknow if that's your issue but it's one data point

 

[dpalmer_2991]

Yes, I think that is exactly the same pistons on my calipers that move more freely!

Did you replace the pistons or did you just change all the seals?

And did it cause any sort of problem under braking like I'm experiencing?

Oh and it's a 2004 model by the way.

Cheers

 

[Popell]

If the powder coating got on the mounting face for the disc then there is zero chance you will remedy by hand to a level of consistancy that would allow the discs to run true (if they are indeed true to start with)

An option would be to find an alloy wheel refinisher who claims to do diamond cut finish and see if he can remove the most minimal amount to clean up the mounting face

A really big lathe might be even better as you woudl mount the wheel off the centre spindle location

 

[NicD]

Yes, I think that is exactly the same pistons on my calipers that move more freely!

Did you replace the pistons or did you just change all the seals?

And did it cause any sort of problem under braking like I'm experiencing?

Oh and it's a 2004 model by the way.

Cheers

depending on how familiar you are with the job, one option woudl be to remove caliper (cable tie brake lever back enough tot engage it to stop fluid running from system), cable tie the other three pistons, open bleed valve and use bicycle track pump to pump out loose piston. Check if it has both seals. If one seal is missing it will come out very easily. You can then refit piston and reattach caliper to brake line. There will be minimal bleeding necessary if you use wooden block as caliper body doesn't retain that much air. You can then decide what to do. fwiw the bmw rebuild kit is better than the motorworks chinese-made one in my experience. it's more expensive but you do the job once.

 

[dpalmer_2991]

Thanks again for the replies, I think if I don't get to the bottom of it by winter I'll rebuild the calipers and see what that does.

As regards to the run out again I'm still unsure if the amount of run out I have would cause that much vibration at the bars. I'm a car mechanic ( I know the brakes are very different on a bike) but that amount of runout wouldn't cause that much feedback at all speeds like my bike does. I wish I knew someone that had a GS that I could just swap the wheel over to rule out a lot of possible options. Just had a quick look on ebay and there's one up for £225, a bit pricey for a stab in the dark.

My main issue is I want to try and find the problem without chucking loads of money at parts that may not need replacing. Especially when all the parts in question aren't cheap!

 

[richtel]

You're feeling judder in the bars when you brake. You say the bearings are good, and I assume you've double checked the headstock for play. Poorly performing calipers are unlikely to show the same symptoms, they'll just be bad at stopping....

A month ago you said-
"Runout on the right side is 0.6mm
Runout on the left side(ABS) is 0.35mm"

BMW say the max runout is 0.15mm (Reprom says 0.15, Haynes says 0.13). Both discs are showing runout either double or four times out of specification.. and if the min and max just happened to be phased in the wrong place you're in a world of pain.

- Wheel out of true (you've not had the tyre rebalanced after refitting so you'd never know)
- Disc mounting posts uneven height
- Discs warped or improperly attached

 

[NicD]

I didn't have any vibration or braking problems with one seal missing

 

[dean0n0]

How do the calipers cause vibration/pumping. Seems to me mounting the discs on plastic coating has caused excessive run out and using the discs like this has buggered them.

 

[autogs]

Its always the same, doing one thing causes a fault, said bod then wades in without thinking and applying some logic veers off into caliper and whatever rebuilds. If it was ok before the powder coating.......
Btw car mechanic ? really!

Sent from my SM-A202F using Tapatalk

 

[ShakeyGS]

How do the calipers cause vibration/pumping. Seems to me mounting the discs on plastic coating has caused excessive run out and using the discs like this has buggered them.

My thoughts also.