s1000rr 2017 - rear brake locks up

[self_moto]

Hello,

No sure if anyone seen that problem, but worth to ask.

So, on last trackday my rear brake (on s1000rr 2017, with ABS) seized completely, to release the wheel had to bleed brake fluid to release pressure. Since then I was trying to figure out what caused it and how to fix it, to make things more interesting - that problem happens only I ride the bike, when bike is not running there is normal amount of drag and travel for rear brake pedal.

Here is what I've done so far:
* bleed brakes + ABS (used moto-scan app to enable ABS bleeding procedure)
* triggered ABS pump and abs solenoids through moto-scan app - all seems to be working just fine, no "unnatural" sound.
* no errors reported in ABS module

After all those actions - problem still persist, after 5 minute ride on parking lot rear brake starts to lock up (was using RACE mode when did the testing)

Did one more thing - unplugged ABS/DTC module completely, which obviously disable any information on dash, like speed, DTC and lean angle information, except gear indicator. Did a test ride - no problem.

At this point - I'm thinking problem is in ABS/DTC module, and it causes bike to constantly "apply" rear brake electronically. I see few options:
* replace ABS module (with used one) - which most likely going to be PITA, since ECU might have to be updated to use new module
* get ABS delete parts from alpha racing and get rid of ABS completely.
* or the problem is in DTC actually, maybe, it "thinks" bikes is about to wheelie and applies rear brake to settle it down (not sure exactly how DTC handles this things).

So, my question - has anyone seen/experienced similar problem? am I missing something that I should have checked?

Thank you

 

[Eric B]

I had similar with an old Yamaha years back. The pads were not retracting when releasing the pedal. Gets hot, fluid gets hot, expands, pushes the pads into the rotor. Gummed pressure release hole in the caliper. Rebuilt caliper fixed that.

 

[Toe]

Do you have aftermarket rearsets? Make sure you have adequate free play at the brake lever. Also like Eric said, make sure your caliper is clean and the piston moves freely.

 

[ST Guy]

And make sure your foot isn’t applying any preeure to the pedal when you aren’ applying the brake.

 

[CrazyCooter]

Definitely check pedal freeplay next as Toe recommended! I've had jam nuts come loose and the rod extend on a couple of different bikes myself.

Next up should you be able to duplicate the dragging issue would be to break the line(or bleeder if equipped) loose at the master cylinder. If that releases the brake, I would then suspect the master cylinder needs rebuilt/replaced.

 

[Lucytriple]

I had similar with an old Yamaha years back. The pads were not retracting when releasing the pedal. Gets hot, fluid gets hot, expands, pushes the pads into the rotor. Gummed pressure release hole in the caliper. Rebuilt caliper fixed that.

I was thinking this too, although it is curious that the problem doesn’t occur when you have the ABS switched off. On the race bikes we often remove the dust seals on the calipers. And if you haven’t already, switch to race brake fluid.

 

[Lucytriple]

It’s worth running the reservoir level a little lower as well.

 

[self_moto]

Thank you for suggestions!

I forgot to mention, I did rebuild the caliper, problem still exists. Having a wild thought - to replace brake pads, thinking behind - since original pads got overheated already more than once, they can not disperse heat anymore and it's causing the temperature start rising, and eventually it lock ups. at this point, just throwing things at the wall to see what sticks

As for brake pedal adjustment - everything seems to be okay, on paddock stand I can easily spin the wheel, and brake pedal has normal travel, but once it heats up - no travel on pedal obviously.

I'm using OEM rear set (ones which used to come with m package I think), didn't have any problems with those for 3-4 years since I installed it.

Also, wanted to mention that it starts locking up within maybe 5-10 minutes, last time by the time I got from pit area to track entry rear wheel already locked up.

Another option I'm considering - replace rear brake master cylinder.

 

[bobl]

There is supposed to be a compensation port of some sort in the master cylinder. This is to allow for heat expansion of the fluid. It means that when the brake lever is off, fluid can flow from the lines and calipers back to the master cylinder. The first part of travel closes off this relief valve, and allows pressure to the system. If this port is blocked, or the lever is partially engaged, heated fluid will apply the brake. Try opening the bleeder when the brake locks. If relieving the pressure frees the brake, problem is port is blocked, lever is closing port, or the ABS module isn't releasing.

 

[bobl]

One thing I forgot to mention is an overfilling of the master cylinder. If there is more fluid than the bellows that allows expansion without exposing the fluid to air can handle, it will put pressure in the system while hot.