[Woopy]

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Today I went for a ride - and it was HOT!
It was 35 degrees and The bike was running in the 90's.
I couldn't get enough air around the engine (speed zones were 80 in the hills) so I decided to go home.
I noticed as I turned very slowly at an intersection that I had no rear brake - the lever had no resistance and it would not lock the rear wheel.

I stopped in the shade and shut down to inspect. The Woodcraft rearset foot peg was very hot, but not as hot as the brake lever which connects directly to the M/C.
Anyway I got home and parked it in the shed. 30mins later the titanium Akras were cold, but the M/C was still too hot to touch!
I can only imagine that I boiled the brake fluid - anyone else ever experienced this with a race system on a fricken hot day? (Normally I would be travelling fast enough to pull hot air away from the bike, but today was just the wrong set of circumstances.

[748R]

Originally Posted by Woopy

Today I went for a ride - and it was HOT!
It was 35 degrees and The bike was running in the 90's.
I couldn't get enough air around the engine (speed zones were 80 in the hills) so I decided to go home.
I noticed as I turned very slowly at an intersection that I had no rear brake - the lever had no resistance and it would not lock the rear wheel.

I stopped in the shade and shut down to inspect. The Woodcraft rearset foot peg was very hot, but not as hot as the brake lever which connects directly to the M/C.
Anyway I got home and parked it in the shed. 30mins later the titanium Akras were cold, but the M/C was still too hot to touch!
I can only imagine that I boiled the brake fluid - anyone else ever experienced this with a race system on a fricken hot day? (Normally I would be travelling fast enough to pull hot air away from the bike, but today was just the wrong set of circumstances.

90's is not very hot mate, up here in qld our bikes sit over a 100 for long periods in our mountain rides. only time i've seen this happen here was on a 916 after improper rear brake install leaving the pad touching the disc which overheated the fluid

[Woopy]

It hit 100+ at an intersection and I turned left and moved on. These bikes shouldn't be pushed at temps over 100.

Anyway - the pads are fine, it was the MC that was boiled!

[pat1098]

I would also say that I have only seen this problem (and too many times!) when the rear pads have a slight drag against them, resulting in boiled fluid, and usually a dragging (or locked) brake.

Just make sure you have freeplay on your pedal linkage. The slightest preload there will cause this exact problem. Strange that your pads and rotor don't show signs of heat/friction. Have a real close look..

Obviously with the master cylinder being mounted against the crankcase it will share the heat of the engine long after the rest of the bike has cooled.

[sweetas]

I boiled the rear brake fluid coming down the Oxley in the pissing down rain. Was as slippery as fuck and wasnt going near the fronts. Rear brake came good after about 5 mins. I did replace the fluid later.

[Moto Corse JP]

Boiling brake fluid? Cant see it happining just like that.
Look at it logically
Ambient temp, although higher than standard atmosphere, wont effect it as much as you think.
Water boils at 212F....DOT standard for uncontaminated brake fluid is 230F
Standard ICAO sealevel temp is 59F
A 40F temp increase in ambient wont boil your fluid.
It may increase the Volume of the fluid by expantion though.
Therefore, you may be dragging a brake, if the MC is bypassing fluid to the caliper.
Now, a dragging brake is a whole new ballgame. We're talking about a sheening of the pads.

[stubbicatt]

Originally Posted by Moto Corse JP

Boiling brake fluid? Cant see it happining just like that.
Look at it logically
Ambient temp, although higher than standard atmosphere, wont effect it as much as you think.
Water boils at 212F....DOT standard for uncontaminated brake fluid is 230F
Standard ICAO sealevel temp is 59F
A 40F temp increase in ambient wont boil your fluid.
It may increase the Volume of the fluid by expantion though.
Therefore, you may be dragging a brake, if the MC is bypassing fluid to the caliper.
Now, a dragging brake is a whole new ballgame. We're talking about a sheening of the pads.

Yes, true, but only part of the equation. As I understand it, the rear brake master cylinder is right next to the engine, which if overheated, could exhibit temperatures significantly higher than the boiling point of water, and at least on my bike, there is an exhaust right near the reservoir. (I have always wondered why).

I think the OP theory is that engine heat boiled his brake fluid. Excessive engine heat because he was unable to get sufficient cooling air through the radiator at the relatively low speeds and high ambient temperature.

[Moto Corse JP]

I get that, and the MC is on the crankcase....but I dont think its a biggy, really, as the rear isnt generating much heat itself, as it's not used much

[ducatista 46]

Put motul 5.1 re bleed
Problem fixed
Can't see how the fluid boiled that hot fluids are designed to see high temps, unless it's that old it failed

[pottebaum]

+1 pat1098. I agree if the rear master cylinder push rod is not adjusted properly then the rear brake could be sticking slightly causing the brake fluid to overheat. The rear brakes would also get hot. You said you have aftermarket pegs. That sounds like the problem. If you grab the push rod with a couple of fingers you should be able to move it slightly. Also if you did not install it correctly it could be at a slight angle causing it to stay activated. The engine heat will not boil your brake fluid. That I 100% guarantee.