Sticking Rear Brake RT 1250

[Tony Fyson]

The rear brake on my 2019 RT 1250 has been dragging, since I purchased the bike new last year. 

The caliper slides on the pins OK, as it can be pushed towards the disc, thereby pushing back the pistons.  When the rear brake is applied and released, the brake drags on the disc.I have been on several rides, where I have not used the rear brake.  Upon checking the rear disc, it was hot, and the brake was dragging.
I have covered over 10,000 miles, and am on my third set of rear pads!

My dealer cannot find anything wrong with the rear brake.Can anyone come up with a solution to the problem?  Has anyone else experienced a dragging brake?
Thanks.

[David.]

Whilst the rear brake caliper may be mechanically functioning correctly, how about the systems which control it, they sound very complicated.

https://forums.bmwmoa.org/showthread.ph ... ked-brakes

[Casbar]

The RT has linked brakes, so even if not using the rear, applying the front will also apply the rears as well.

[exportman]

Even with Linked brakes the disc should only be hot if they have been recently used and quite hard.  The OP does not mention the Front brake temp.
I have a 2017 1200 rt as do a few of my riding buddies.  There is a tendency for the rear brakes to get a little sluggish to release, and need attention every now and then to clean up around the pistons and sliders.  But this is a trait across many bikes not just BMs

[Casbar]

Even with Linked brakes the disc should only be hot if they have been recently used and quite hard.  The OP does not mention the Front brake temp.
I have a 2017 1200 rt as do a few of my riding buddies.  There is a tendency for the rear brakes to get a little sluggish to release, and need attention every now and then to clean up around the pistons and sliders.  But this is a trait across many bikes not just BMs

Agree, but the OP did say his rear brake disc was hot even though he hadn't used the rear brake, so I was just pointing out, if he was using the front brake, the rear would still have been used. Got to say, can't say I have ever bothered to feel my rear disc

[ymfb]

A few years ago there was a lot of similar complaints on UKGSER, as a result I bought a complete set of pads, for my 2016 GSA.  IIRC the fronts did 18,000 before they needed changing and the rears still had plenty of material left at well over 30k miles.


As Casbar said these bikes have linked brakes and when you operate the front it also engages the rear.  I read somewhere the rear brake is actuated a split second before the fronts engage.  When I asked a dealer about pad wear they told me it’s largely down to the riding style, people who live in big cities use pads, advanced riders from rural areas don’t.


More recently my 1250 GSA‘s front brakes had a squeak after a tyre change, when I pulled the pads to clean them they were bone dry on the backs so after cleaning I lightly smeared the backs with copperslip grease.  Maybe the OP might pull the pads, clean them and consider using one of the specialist compounds on the backs of the pads.


I’ve never considered touching my brake discs to see how hot they get as I don’t need burnt fingers.

[Tony Fyson]

Thanks for the various replies.My dealer advised that he could not find anything wrong with the rear brake, but is still does not fully release - whether it was activated by the linked front brake, or the rear brake lever on its own.
I have tested the rear brake as follows:

• Put bike on centre stand.
• Push caliper towards the disc, thereby pushing the pistons further into the caliper.  Rear wheel spins freely.
• Apply rear brake only.  Rear brake drags - indicative that the pistons are not being retracted by the seals, when brake pressure is removed.

As stated earlier, my dealer could not find anything wrong.  Is there some sort of pressure relief valve that could be stopping the pistons from retracting, when the brake pressure is released?
I have checked the rear brake after several sweeping country road rides, where I have not used the rear brake, and minimal use of the front brake - disc was hot.Commuting 4 miles in 30mph zones, without touching the rear brake - disc gets hot.
Any help would be appreciated.

[Graham88]

Is your dealer suggesting there is nothing wrong with the bike or that there is something wrong and they cannot find it?

[Tony Fyson]

HiI have just emailed my dealer, explaining how I removed the caliper, cleaned the pistons with brake cleaner, applied a thin smear of silicone grease to the piston walls, and pushed the pistons back into the caliper.I pressed the rear brake pedal, and observed the pistons move out, but they did not retract when I released the rear brake pedal.
This would suggest that the piston seals are faulty.
I am waiting for a reply from my dealer.  I am very disappointed with my dealer, who has not been able to fix the problem.

[David.]

I have covered over 10,000 miles, and am on my third set of rear pads!

Were the pads changed FOC by the dealer? This is clearly premature wear.

In 2018, I had both front brake calipers replaced on my 2012 Camhead under an insured warranty. The calipers were partially seized and brakes binding. Although not worn out, the pads were replaced under what is called "Consequential Damage". Damaged caused to a covered part by another covered part.

Go into the showroom and checkout the rear brake on a new bike or a demo bike. You might be surprised at what reaction you'll get then, especially if someone is looking to purchase a new bike at the time!

[David.]

This might be helpful.

Recently had a query with respect to the cover provided by the BMW Insured Warranty. Phoned the 0345 number in the policy handbook, was then given a phone number of 01252 920 125. I believe this is for the Insured Warranty claims department in Farnborough. I was told that BMW Motorrad (UK) were in the same building along the corridor. I was given an email address of [email protected] Using this address, via the claims dept. they were able to speak directly to BMW Motorrad (UK) on my behalf.