Temporary loss of rear brakes

[marcopol]

Strange thing happened to me the other day. I was fairly shifting the bike for an hour or so around some mountain roads (the Beara pennisula in Ireland) when I evetually came around a tight bend to discover that I had just lost my rear brakes. The pedal went right done with no effect. Pumped it like hell and it eventually came back. This occurred for the rest of the day. Eventually got back to base and checked for leaks or loose connections and there were none. The rear brake resevoir was full. Next day I get back on the bake and hey presto the rear brake is working fine. Anyone ever come across this.
The bike is a 2000 R1150 GS non ABS

 

[justabof]

When was the fluid last changed? The symptoms sound like old fluid, which has absorbed water, which is heated-up by the heavy use of the brakes. The water boils and turns to vapour and you lose all pressure.
When it all cools down again, it seems normal, but the problem will arise every time the fluid gets hot.

 

[MikeO]

I had a similar problem when abusing my rear brake over a series of gravel covered switchbacks. I was expecting it, as I was riding a bit like a hooligan, racing a thunderstorm home (I won - just).

It will mean your rear brake got very hot. I discovered the consequence of this several months later when changing the rear tyre...

Mike

 

[marcopol]

When was the fluid last changed? The symptoms sound like old fluid, which has absorbed water, which is heated-up by the heavy use of the brakes. The water boils and turns to vapour and you lose all pressure.
When it all cools down again, it seems normal, but the problem will arise every time the fluid gets hot.

No idea when the fluids were last changed. I only have this GS 3 weeks.

 

[Myke Rocks]

Probably very little to do with fluid needing changed.

When was the fluid last changed? The symptoms sound like old fluid, which has absorbed water, which is heated-up by the heavy use of the brakes. The water boils and turns to vapour and you lose all pressure.
When it all cools down again, it seems normal, but the problem will arise every time the fluid gets hot.

When we went road rallying a lifetime ago, serious abuse could lose the rear brakes in a matter of 10 miles or so especially when the brake balance was moved a lot to the rear to give good "turn in". This was done both for turn in, and, since I always left foot brake in such circumstances, I then kept the accelerator pressed enough to "kill" the rear brakes when the need arose.

The downside was loss of rear brakes on a car with fresh Dot4 in it.When this happened, we usually moved the balance forward a little and pumped the brakes when they were required. To give you an indication of how hard we were using the brakes, I had 2 similar cars, 1 for road rallying and one for road use. Road car brake pad life 30,000 miles. Road Rally car brake pad life: 100 miles.

Cure on a motorcycle:
make sure brake pads are fairly new. There is very little meat on them to start with. Trust the standard brakes and don't use the rear pedal.
Go a little gentler.
Myke

 

[The Grey One]

I had exactly the same melting of the gaiter when the local BMW dealer adjusted out the free play out of the rear brake pedal. Check you have the correct amount of free play and change the fluid anyway.

John

 

[Welshman]

No idea when the fluids were last changed. I only have this GS 3 weeks.

Change the fluids, seen it here in the mountains, if they haven't done the brakes bleed the clutch as well

 

[Dragon Master]

OK, similar problem, R1100GS ABS. About six weeks back I was decending the Hardnott pass when I lost the rear break; made life somewhat interesting for a few minutes. Stopped at bottom and had a play with the lever, but no joy, so decided to carry on carefully. About half way to the bottom of Wrynose pass, rear brake re-appeared.
When I got home I checked pads, they were down to about 1mm, so repalced them. I've had no problem since, including doing the RBLR1000, until last Saturday. Having ridden the road from the M6 (J41)to Wigton, when I came to stop in Wigton, no rear brake. I had a poke about with the lever, and they came back. But I did discover both caliper and disc were very hot. (Managed to brand a nice circle device on to my finger end)

On Sunday, decending Winlatter pass, no rear brake when I got to Lorton. Poured a bit of water on caliper and it hissed and spat before boiling off. Again, few minutes wait and play about with lever, and the brakes return.

Now, I can't feel any play in the output bearing. I can roll/push the bike about quite freely. I can spin the wheel quite freely on centre stand. A 2-3 mile run without using rear brake, no probes with heating. But <1 mile run with one light use of rear brake, and caliper is getting warm.

Roy at RGM suggested I'd adjusted the free play out of the lever, so I made sure there's about 1.00mm. I've just stripped and cleaned the caliper again, but it's still binding very slightly.

Fluid change? (Must be due, I've had the bike 2 years now), or any other ideas?

Oh, and I always ride with my foot turned out away from the pedal, so any use of brake is a concious effort.

Cheers,

Dave.

 

[Smug]

If you constantly drag the rear brakes in the mountains then they will eventually overheat and fade. Try controlling your speed more with the throttle and using the correct gear.

 

[Dragon Master]

If you constantly drag the rear brakes in the mountains then they will eventually overheat and fade. Try controlling your speed more with the throttle and using the correct gear.

The way you suggest, that is the way I ride, and have done for the past 30 years. But when you need to stop on a Hardnott hairpin, you need to use the breaks. The other two occasions I was using the rear brake for the final stop, (leveling out) having slowed down with engine braking/front brake.

 

[Dragon Master]

Bit more...
I took the caliper off yesterday and gave it a good clean-up. Both pistons are moving smoothly, both in and out (or should that be out and in?)
Took the bike for a short run, about two miles (no mountains involved), without using rear brake. Checked at end, and caliper and disc nice and cold.
Did same run again, but used rear brake just the once to slow the last few yards (from ~ 10mph to stop) at first junction. Checked when I finished, and caliper/disc were warm.
Oh, and I've increased the free play at the pedal to ~5mm, and still keep my foot turned out away from the pedal unless I'm actually using the brake.
Roy has suggested the master cylinder piston might need a bit of rubber grease. I've done a search on here to no avail, anyone know of any 'how to' picture sequences for stripping the rear master cylinder?

 

[Bubb]

brake fade

another possibility is that the roads were bumpy enough to push the brake pistons back into the callipers, therefore having no brakes when first tried.....
pumping them will bring them back.....worse if the pads are low.

Bubb

 

[MikeO]

another possibility is that the roads were bumpy enough to push the brake pistons back into the callipers, therefore having no brakes when first tried.....
pumping them will bring them back.....worse if the pads are low.

Bubb