Front brake binding

[HPNer]

Strange issue on my morning commute riding my rusty old 2009 1200GS SE (Non-electric servo)
I had an intermittent front brake bind. On getting off it was the rotor on the ABS wheel side (near side) that nearly burnt my finger off when I tried to identify the offending disc. The other two rotors were warmish.
No red or amber lights coming up on the info screen.
I guess it must be a sticking piston, any ideas for the cause? The bike lives outside is used everyday and throughout the winter. Anyone here had a similar issue and how did you fix it?
Grateful for any responses.

 

[Bendy toy]

It's a sticking piston.

The original pistons are metal and corrode so it's likely the seals are shot. BMW sell seal and piston kits for £60 a calliper. Or get a used calliper off eBay, strip, clean and grease with red rubber grease.

I use a clamp made from steel strip to hold a piston with a block of wood between the other two. The free piston can be pumped out. Carefully remove the seals, clean grooves and seals, grease with red rubber grease and replace.

Swap the clamp to the replaced cleaned piston and repeat until all are done.

Then do the other calliper it won't be far behind.

Badly stuck pistons need the hydraulics to get them out. Less bad will move with a bicycle tyre stirrup pump and air bed adapter.

Sent somehow.

 

[HPNer]

Thanks!
A quick scoot around ebay beckons!

 

[Greenman14]

Before you start stripping brake callipers it's worth trying to free off each individual piston. The pistons should be free enough to push back with your fingers only. A wooden wedge between 2 pistons and a small G clamp to restrain the third will let you exercise and free off each piston in turn. This is a routine you really ought to do twice a year. Good luck.

 

[JJH]

With salt on the roads at the moment it's no harm to keep the brakes free by pushing them back and then pumping back out. You can push back calliper by placing your foot on it and hold the bike just posh with your foot. Do not forget to pump out the pads again or you will crash. It takes 15 strokes of the lever to bring worn pads out to contact the disc PER SIDE so that's 30 panic pulls you would be dead. JJH

 

[boatman]

I have had this exact same thing happen on 2 of the 1200 , GSA ,s
It might be the piston , but it's much more likely to be the pads sticking in the calliper .
The berm on brakes are built to quite tight tolerances, the pads jam at the ends.
If you pull the pads, grind / file about 10 thou off each end , take the resulting burrs of , put a very very light smear of copper slip on the ends, it won't do it any more

 

[Kenny Rodkiss]

With salt on the roads at the moment it's no harm to keep the brakes free by pushing them back and then pumping back out. You can push back calliper by placing your foot on it and hold the bike just posh with your foot. Do not forget to pump out the pads again or you will crash. It takes 15 strokes of the lever to bring worn pads out to contact the disc PER SIDE so that's 30 panic pulls you would be dead. JJH

You'll have a tough time trying that on GS/GSA front brakes. They are not sliding callipers so do not move. You can push on the rear sliding calliper to push the rear brake pistons in.

 

[Bendy toy]

I needed new pads and found two pistons were sticking. Strangely there was no uneven wear on the pads.

I tried exercising the pistons. But one was very stiff so a strip down was the only option. The cleaned pistons moved 1000% more smoothly. So IMO it's best to bite the bullet and do the job properly.


Sent somehow.

 

[JJH]

You'll have a tough time trying that on GS/GSA front brakes. They are not sliding callipers so do not move. You can push on the rear sliding calliper to push the rear brake pistons in.

I was referring to back brakes. I missed 1 "back" so it should read "push back back brake calliper" just to clear that up. Fronts are done with a big screwdriver. JJH

 

[HPNer]

Again, thanks!
Evertything fine today, but looks like spanners out this weekend . .!

 

[patzx12]

I have some calipers off an 05 if you need replacements.