Heat in rear brake disc 2010 R1200 GSA

K9Morris

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Fitted new rear disc and pads. Took it for a test ride and checked the disc and it was hot. Had it off and on several times but still gets hot. Had it in local garage on rolling road and they confirm it’s not binding. They’re bemused-as am I. Anyone experienced this? Any help would be appreciated.
 
Linked brakes.

Unless you roll to a stop on a road where you haven't applied the brakes for several minutes - that will be the cause
 
Hot is normal as brake pads touch slightly the disc, if it changes color then that is not good, but a disc always gets hot, and as op says above linked brakes, when you use the front it brakes at the rear also.
 
Get some temp stickers on it, or a digi thermometer and see what the temp is.

To much heat will warp the disk or flick some water on it , if it boils off its a tad too hot ;)

sounds like a sticking caliper

one pad will be in contact with the disc. dosent need much but the friction will generate loads of heat

had the same on the wifes car one disk getting bloody hot , stripped and cleaned / freed / lubed the caliper, to no avail.

Only fix was a new caliper ---

Dont leave it to long, or you may need a new disk & pads too
 
Thanks for the comments guys. Calliper moves freely on the slides and isn’t sticking. 20 mike ride trying not to use the brakes garage tell me the disc measured 30 degrees. Next ride using the brakes it measured 60 degrees. Front brake doesn’t get as hot. Also, when I put the bike on the centre stand, start it up and put it in gear it sounds like the back end is gonna drop off! Garage says this is due to no weight/load on the final drive. Does this sound right?
 
Garage sounds on the money.
Rear end doesn’t like being run”unloaded”.

I have servo linked brakes and pretty sure rear disc doesn’t get too warm but they are certainly linked. Don’t know what component does the “apportioning “ on your year but you might need to see if that’s working/clean. Time for a fluid flush?
 
The linked brake system uses the rear brake quite heavily, even more so when the front brake is used gently. If you suspect the brake is binding, switch off the ABS and ride the bike without using the brake pedal. If disc is still hot, then its likely the caliper is binding.

The rear master cylinder on older bikes has a poor dirt cover. Eventually the shuttle will stop moving properly and jam the brake on.

IMO, simply exercising the caliper pistons is only ever a temporary fix. You can get a replacement seal kit for the caliper from BMW for about £20. Its not a difficult job and solves any caliper hydraulic issues.
 
Why did you replace the disc? Only asking to see if problem existed before and warped the disc through heat. Or is this a new problem?
My 08 GSA rear disc needed replacing as it was binding, causing heat, despite the rebuilt caliper moving freely on good pins.
Replaced the m/cyl - no change. Replaced the caliper with a good used one and problem solved. Still have the old one, but had it apart countless times and couldnt see what the problem was with it.
So, bottom line, dont rule out anything and replace everything. That should sort it.
 
plus 1 what bendy said. Had similar issue on my 1200, replaced seals and cleaned pistons properly. Problem went away
 
During this years trip the pads wore down to metal and gouged the disc quite badly so replaced it once we got back. Tbh I’ve never checked the temp of the discs prior to this issue which is why I’m asking for advice from folk who may have experienced something similar.
 
During this years trip the pads wore down to metal and gouged the disc quite badly so replaced it once we got back. Tbh I’ve never checked the temp of the discs prior to this issue which is why I’m asking for advice from folk who may have experienced something similar.

The BMW OEM organic pads are not suitable for ABS bikes. The linked brakes will chew away those pads in under 4000 miles. My new disc got scored but thankfully not too badly by exactly that issue. I now have Ferodo top level organics in the back. They have lasted better but they wont be up to sintered pad life. IMO sintered pads over-brake the back end.

The caliper is only rebuilt if you pop the pistons clean thoroughly and fit new seals. Corroded aluminium in the seal grooves = the problem will return quite soon as corrosion builds up again. Mine has now done 70K with seal done at 50K. The sliding pins are fine.

If you suspect the master cylinder, simply crack the bleed nipple open. If the fluid is under pressure you have a sticking master cylinder.
 
To the OP,

In short, There are ony really two ways the disk can get hot

Ambient heat soak from another source -
Very unlikly, you'd know if you had a hot diff or transmission tunnel. ;)

Contact / friction - Somthing is contacting the disc or rubbing against the disk.

If you want to prove it - And you do this at your own risk!!!!!!!!

Pop out the rear pads and push the caliper / pistons back

Go for a short ride and use the front brake only!!!!! check the temp in the rear disk

If the disc is cold, (and id put money on it being cold) pop the pads back in, press the brake a few times to bed the pads, and do the same route, using front brake only again ...

If the disk is hot its the caliper/ pad,s / disc relationship there really isnt any other way the disc gets that hot.

Check your runout on the disc it could be warped !

As i said in i think post 3 or 4 had exactly the same in the wifes car. only cure for her was a new caliper.

Try Bendy's method first, check the disc runout, if not then it's service the caliper / pistons for

£30 odd If it works job done,

If not its a new / refurb caliper / disc there really is no other route to go
 
I cant agree with that advice to take out the pads and ride. If the disc was warped to any extent it would push the pads away. I would be looking at the pistons and the pins that the calliper slides on. I find those very vunerable to collecting dirt and sticking even with my method after almost every winter ride place hand on pillion grab handles/rack place foot on calliper and push calliper in.pump brake to bring everything back.you may have to do this a few times. Striping and cleaning is a regular nessededy. JJH
 
I cant agree with that advice to take out the pads and ride. If the disc was warped to any extent it would push the pads away. I would be looking at the pistons and the pins that the calliper slides on. I find those very vunerable to collecting dirt and sticking even with my method after almost every winter ride place hand on pillion grab handles/rack place foot on calliper and push calliper in.pump brake to bring everything back.you may have to do this a few times. Striping and cleaning is a regular nessededy. JJH

Yeah - a bit nuts.

It's a bike with linked brakes, so the system will pump the pistons into the disc - and probably empty the master reservoir.
 
I cant agree with that advice to take out the pads and ride. If the disc was warped to any extent it would push the pads away. I would be looking at the pistons and the pins that the calliper slides on. I find those very vunerable to collecting dirt and sticking even with my method after almost every winter ride place hand on pillion grab handles/rack place foot on calliper and push calliper in.pump brake to bring everything back.you may have to do this a few times. Striping and cleaning is a regular nessededy. JJH

Yeah - a bit nuts.

It's a bike with linked brakes, so the system will pump the pistons into the disc - and probably empty the master reservoir.

Before you both go all self righteous lol- it was a suggestion nothing more. :D

And if you'd paid attention ;), the op has allready run his rears metal to metal, so he's hardly a saint ;) and thats just as bad as no pads ;)

Tbh, I thought the linked brakes was only on pre 2008 models,

so if not, on that count fair enough my mistake.

Either way his fault is either disc, caliper or master piston

My moneys on the caliper
 
I don't want to be rude but DO NOT RIDE THE BIKE WITHOUT REAR BRAKE PADS. The test is relevant of course.

An ABS bike will always apply the back brake when the front lever is used. If there are no pads you risk the pistons hitting the discs or worse. The simple test for ABS bikes is to switch off the ABS or disconnect the speedo sensor (does the same job) and do not touch the brake pedal. On Non ABS bikes, simply do not use the back brake.

If the brake then runs cool you know the issue is caused by the ABS/linked braking being over-enthusiastic. There is no fix other than not using the ABS.

To the OP,

In short, There are ony really two ways the disk can get hot

Ambient heat soak from another source -
Very unlikly, you'd know if you had a hot diff or transmission tunnel. ;)

Contact / friction - Somthing is contacting the disc or rubbing against the disk.

If you want to prove it - And you do this at your own risk!!!!!!!!

Pop out the rear pads and push the caliper / pistons back

Go for a short ride and use the front brake only!!!!! check the temp in the rear disk

If the disc is cold, (and id put money on it being cold) pop the pads back in, press the brake a few times to bed the pads, and do the same route, using front brake only again ...

If the disk is hot its the caliper/ pad,s / disc relationship there really isnt any other way the disc gets that hot.

Check your runout on the disc it could be warped !

As i said in i think post 3 or 4 had exactly the same in the wifes car. only cure for her was a new caliper.

Try Bendy's method first, check the disc runout, if not then it's service the caliper / pistons for

£30 odd If it works job done,

If not its a new / refurb caliper / disc there really is no other route to go
 


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