Rear Brake Master Cylinder Heat - Ducati Supersport 939 Forum
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post #1 of 20 (permalink) Old 06-30-2019, 11:31 AM Thread Starter
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Rear Brake Master Cylinder Heat

Not sure if this has been mentioned before, after a ride yesterday I felt the rear master cylinder, I couldnít believe how hot it was. The ambient temperature was 34C, 93F the hottest day of the year so far, I didnít measure the temperature of the master cylinder but I couldnít keep my hand on it. With it getting that hot the brake fluid must be close to boiling or at the very least it has to affect the rear brake performance, could explain why the rear brake is not the best.
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post #2 of 20 (permalink) Old 06-30-2019, 12:38 PM
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Not sure if this has been mentioned before, after a ride yesterday I felt the rear master cylinder, I couldnít believe how hot it was. The ambient temperature was 34C, 93F the hottest day of the year so far, I didnít measure the temperature of the master cylinder but I couldnít keep my hand on it. With it getting that hot the brake fluid must be close to boiling or at the very least it has to affect the rear brake performance, could explain why the rear brake is not the best.
Interesting, Iíll check when I ride in a little while. I have not had any issues with performance of my rear brake under varied road conditions.

Did you lightly or fairly heavily use the rear before noticing this?

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post #3 of 20 (permalink) Old 06-30-2019, 01:01 PM Thread Starter
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Did you lightly or fairly heavily use the rear before noticing this?
I didnít use the rear brake at all, I was looking at the bike (a post ride inspection) when looking at the right hand side I felt the heat radiating from the exhaust. I touched the foot peg and that felt hot then I touched the master cylinder and was shocked at how hot it was. I suppose itís heat transfer from the cat.
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post #4 of 20 (permalink) Old 06-30-2019, 01:54 PM
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The rear tire in the section next to the exhaust gets pretty hot too, just sitting there after a ride...

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post #5 of 20 (permalink) Old 06-30-2019, 04:20 PM
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Just rode for about 1.5 hours in 95 F heat. Stopped at station for pit stop. Reservoir was just a little warm to touch, definitely not hot. But I was moving continuously, no traffic.

The topic of the rear brake on this bike and some other Ducatis is the subject of much debate here and elsewhere.

But imo, my rear brake is fine. Something to consider is that the ABS is so refined on this bike that if one just uses the rear and pushes it a bit, without the front, the ABS will prevent lock up. That might appear like itís an issue with the pad or boiling point...when itís actually the ABS doing itís thing. Not saying there arenít better pads, or fluids, but the set-up is fine for my pretty aggressive street riding style.
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post #6 of 20 (permalink) Old 06-30-2019, 05:27 PM Thread Starter
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@Ed K itís a good point you made about continuously moving, my journey was coming home from work. About an hours journey with a lot of filtering and slow stop start traffic. I will monitor it with a better journey. As we know the SS can get a little on the warm side if not moving.
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post #7 of 20 (permalink) Old 06-30-2019, 05:38 PM
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I am surprised that someone doesn't sell a heat cover. Especially with all these carbon doodads.
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post #8 of 20 (permalink) Old 07-01-2019, 11:50 PM
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Something to consider is that the ABS is so refined on this bike that if one just uses the rear and pushes it a bit, without the front, the ABS will prevent lock up.
sooo.....you are recommending rear brake only when riding twisties??? Rear brake trail braking....since it will be prevented from locking up??
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post #9 of 20 (permalink) Old 07-02-2019, 12:22 AM
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Rear brake fluid overheating/boiling is a common issue on SS & Monster. It is due to proximity of brake line to CAT. As for master cylinder it is also very close so I suspect that may be cause in heavy slow moving traffic? Might want to check free-play in rear pedal and rear disc temp just to be safe?
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post #10 of 20 (permalink) Old 07-02-2019, 04:10 AM
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There has been a lot of discussion about Ducati rear brakes on the UK Ducati forum. The consensus appears to be to use a synthetic fluid with a high boiling point like Motul 660.
I've been using this RaceTech stuff in my bikes for a few years now with good results.
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