Last year my rear brake started to stick. I have wintered the bike in my garage and today took the rear caliper off. One of the pistons was sticking so freed it off and cleaned up both calipers using soapy water and a tooth brush. After a quick ride all was working fine for about ten minutes. Then, after a rear brake application, the pedal became solid and the rear brake started to drag badly. I put it on a stand at home and the wheel was hard to turn until it cooled down. Even then the brake would lock again and the brake pedal harden up until the disc had completely cooled. Once cool it all seemed fine. Is it the adjustment, a piston problem or some kind of hydraulic issue? Many thanks.
You need a bit of play in the adjustment rod, if it is adjusted with no play at all, your symptoms will occur. Steve
Ok, I’ll look at the master cylinder. Thanks. I’ve tried adjusting the rod to the point where the brake hardly works but still it locks on. How much free play is needed? Probably a stupid question but is the free play at the pedal itself?
Yep free play at the pedal, I think I have three or four mm of play in the rod on mine, just a rough idea, I found the adjustment by trial and error. It is well known to stick on if there's no play. Steve
totally agree - a few threads on here about this already. Heatsoak due to m/cylinder being next to exhaust can create a real problem and worse in hot weather.
Check your reservoir.Overfilling causes this problem too.I did it once and it was okay here, but by the time I reached Paris i had the same problems as You.We removed a little fluid and I was good to go.
a rare occurrence but a blocked reservoir cap breather will do the same also, had this happen on an Elefant once.
I had exactly the same problem when I first got my 916. I put a new master cylinder on and it solved it.
Had this with the front brake of an R80/7 once. The only time I was ever grateful that the brake were total crap.
Thank you all for your help. The brake only ever locked on when the engine was warm so a sticking piston seemed unlikely. I have removed some of the hydraulic fluid and all seemed back to normal yesterday on a short test ride. Whether it was the fluid amount or a (now unblocked) breather issue I don’t know but all seems well. Thanks again.
Sorry to be a bit of a doom monger, but I did a similar thing and the problem returned. I hope that I am wrong. A new master cylinder is around £50 if you need to go there, so not too bad.
a replacement master cylinder is the last option I would try in all the above list of adjustments and corrections that can be tried first at little cost.
Absolutely and I did the same, taking the great advice on this forum. I am just saying that was what I ended up doing.
I think you'll find that it's the disc heating up due to the pads being in constant contact that is causing the problem, the engine warming up at the same time is coincidental.
Had the same problem, new master cylinder fitted, front and rear fluid now silicone, so no more moisture or heat prob's
