Why did my rear brake caliper melt?

[dino74]

So I was at the track this weekend. During the warm up orientation laps, it seemed like my engine was lacking power. It was weird, it sounded good but no power. Power was restored about 3-4 laps later, figured it was due to the bike sitting for 2 months. Later in the day I saw this. It don't know what to think...

BTW: The reservoir was still full and I didn't touch the rear brake the whole day.

[k-os]

Are your pistons seized and caused your rear brake to keep pressure on the disc, therefore heating it up and deforming the aluminum caliper?

[Kevin2109]

Not much help here but on OC moto the same thing happened to someone else, A reason why was never found :/

[CC Cowboy]

In the first picture you can see tons of crud on the pistons. I suspect they couldn't move so the pads were stuck.

Wasn't the bike hard to push around before the race?

[alex.s]

look at how far the piston is pushed out. the crud was on the inside. your brake fluid in the caliper is probably disgusting. when was the last time you cleaned it out?

but.... why would it keep pushing out... did the fluid boil and put even more pressure on? something had to keep putting pressure in that caliper...

[k-os]

Originally Posted by alex.s

look at how far the piston is pushed out. the crud was on the inside. your brake fluid in the caliper is probably disgusting. when was the last time you cleaned it out?

but.... why would it keep pushing out... did the fluid boil and put even more pressure on? something had to keep putting pressure in that caliper...

I'm sure if the caliper heated up enough to deform it, the fluid inside it was boiling.

[dino74]

Originally Posted by alex.s

look at how far the piston is pushed out. the crud was on the inside. your brake fluid in the caliper is probably disgusting. when was the last time you cleaned it out?

but.... why would it keep pushing out... did the fluid boil and put even more pressure on? something had to keep putting pressure in that caliper...

Yeah, I usually clean out the caliper when I change the pads, but its been years since I changed out the rear pads. I think the crud on the inside are the melted rubber rings.

I'm guessing there was slight pressure on the pads and it just got hotter and hotter until it boiled. Its a no brainer that the caliper is hosed but I'm wondering if a malfunction in the master cylinder could have caused it. I was wrong about the rear brake not being used. It was pressed during tech. I'm probably going to replace the master cylinder just to be safe.

[alex.s]

i wonder how much rotational weight the rear brake disk is... it weighs a few pounds right?. . . . . . hmmmmm

[dino74]

Originally Posted by alex.s

i wonder how much rotational weight the rear brake disk is... it weighs a few pounds right?. . . . . . hmmmmm

I don't use the rear brake at all ... except when I run off the track into the dirt

[jasle]

Originally Posted by CC Cowboy

In the first picture you can see tons of crud on the pistons. I suspect they couldn't move so the pads were stuck.

Wasn't the bike hard to push around before the race?

+1. Brake fluid is hydroscopic and absorbs water. You should change fluid every 24 months at a min. I'd do 3-4 if you're on the track. From a sealed bottle every time. The one sitting on the shelf has been absorbing water since you bought it and broke it open.
The pistons rust in the bore and stick. I'd suspect this is what happened.

[Nemesis]

Too much crud around the piston can cause your pistons to seize and as a result that is what happens.

Any time you change out your tires always spin your wheels and make sure they spin at least one full rotation. If not, you got issues.

That's what happened to me on my trackday Nov. @ Buttonwillow. My front wheel wouldn't even spin half a rotation. You can see in this vid Rexbo took where my entry speed was faster but he'd catch me easily in the straights.

Link to original page on YouTube.

Got home, pull the front wheel & brakes apart and one of the pistons had seized (fully extended) so it was always applying pressure.

[Nemesis]

Oh Dean I have an extra rear caliper if you need it. LMK>

[Skippii]

Your caliper melted because it got too hot. Glad I could help.
Posted via Mobile Device

[dino74]

Originally Posted by Nemesis

Oh Dean I have an extra rear caliper if you need it. LMK>

Thanks for the offer! But I've got a second ninja to pull parts from.

[dino74]

Originally Posted by Skippii

Your caliper melted because it got too hot. Glad I could help.
Posted via Mobile Device

Skippii, where have you been all my life?

[Nemesis]

Originally Posted by dino74

Thanks for the offer! But I've got a second ninja to pull parts from.

WTF?

I'm sorry....baller!

[alex.s]

Originally Posted by Nemesis

That's what happened to me on my trackday Nov. @ Buttonwillow. My front wheel wouldn't even spin half a rotation. You can see in this vid Rexbo took where my entry speed was faster but he'd catch me easily in the straights.

Link to original page on YouTube.

Got home, pull the front wheel & brakes apart and one of the pistons had seized (fully extended) so it was always applying pressure.

sure, blame the brakes.

[Nemesis]

Originally Posted by alex.s

sure, blame the brakes.

Ahhh, my padawan is learning fast.