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Old 05-03-2015, 10:29 PM   #1
tomdubz OP
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Rear Brake Fire

Well, I went and rebuilt by brembo brake calipers all around on my KTM 990.

Similar to this: http://www.ktm950.info/how/Orange%20...ndon_rear.html

Was confident that they were solid after going for a quick 10 min ride around the block last week. But I was wrong. I went for a longer ride and stopped for gas. Low and behold my rear brake was on fire - lost pressure, fluid squirting out the pistons when pressing pedal, cooked/melted pads, and gunk all over the caliper. After getting a fire extinguisher on the scene, I was able to limp home w/o using the rear brake. I kept testing the front on the way home, activating the abs a couple times, worried that they would fail too. They did not. I'm assuming I did something horribly wrong with the seals on the rear.

The questions:

Do I just order another caliper or could I possibly salvage the old one? It was on fire and my instincts tell me to just break down and get another. Anyone with experience?

Will I be able to get the cooked gunk off the rotor or am I looking at buying a new one of those too?

And... should I be worried about the fronts or would they have failed by now if they were going to?
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Old 05-03-2015, 11:47 PM   #2
PeterW
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The rear is likely "too much fluid" I did it myself on an F650, but not to the point of flames. You fill the system THEN fit the pads and assemble, which pushes the pistons back and pushes fluid back into the reservoir - oops - overfull - which has the same effect as riding with a foot on the brake lever.

Pull the caliper down, if the bores aren't scored, likely still usable. The brake disk, well, if you can get the gunk off, probably fine. But I'd certainly toss the pads away.

Effort though, if you put a $ value on your time likely a lot 'cheaper' to just buy a new rear caliper and be more careful next time.

Fronts, check the fluid level, if it's in the normal range, probably O.K.

No promises in any of that, but having done similar once - my best guess.

Pete
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Old 05-03-2015, 11:55 PM   #3
tomdubz OP
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Quote:
Originally Posted by PeterW View Post
The rear is likely "too much fluid" I did it myself on an F650, but not to the point of flames. You fill the system THEN fit the pads and assemble, which pushes the pistons back and pushes fluid back into the reservoir - oops - overfull - which has the same effect as riding with a foot on the brake lever.

Pull the caliper down, if the bores aren't scored, likely still usable. The brake disk, well, if you can get the gunk off, probably fine. But I'd certainly toss the pads away.

Effort though, if you put a $ value on your time likely a lot 'cheaper' to just buy a new rear caliper and be more careful next time.

Fronts, check the fluid level, if it's in the normal range, probably O.K.

No promises in any of that, but having done similar once - my best guess.

Pete
Thanks for the insights but I fitted pads, THEN filled and bled. Maybe I didn't get all the air out in my bleed. Could've expanded and pressed the pads continuously.
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Old 05-04-2015, 12:14 AM   #4
PeterW
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Originally Posted by tomdubz View Post
Thanks for the insights but I fitted pads, THEN filled and bled. Maybe I didn't get all the air out in my bleed. Could've expanded and pressed the pads continuously.
You can usually pick air from the spongy feel, yes it will do that, but if there's that much it's usually obvious immediately.

Old brake fluid with water in it, or water in the system before filling is a possibility (much bigger volume change than cold->hot air). If you didn't use a freshly opened container of fluid the fronts are definitely suspect as well.

If none of those are to blame and you assembled everything properly, a bit of solid crap in the system jamming in the exit port from the calipers will also do this - though, you've torched any evidence there .

Pete
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Old 05-04-2015, 11:24 AM   #5
dwayne
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Also on a BMW F650GS dakar. I found the rear master cylinder was hanging up the piston and not releasing pressure. There is a nylon sleeve to guide the piston in the non pressure portion of the cylinder bore. The nylon can collect dirt, get scored, out of round etc... I never lit the brakes on fire, but I could feel them drag and had to release them using a screw driver, knife etc.to pry back the pads.
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Old 05-04-2015, 02:16 PM   #6
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I'd be worried about the heat of the fire changing the metallurgy of both the caliper and rotor.
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