OH NO! Did I just cook my rear disk!?

[TINK_imp]

So I come home after a short ride this morning, put the bike up on the center stand, spin the wheel to lub the chain... spin the wheel... Houston, We've Got a Problem.

It seems that the rear brake is dragging, excessively. So much so that the rear disk is showing signs of blueing, overheating.

The brake pads are brittle in places and small chunks of pad have broken off.

WHAT THE HECK IS GOING ON HERE!?

Could I have unknowingly had my foot on the rear brake pedal, thus overheating the rear brake? If so, then why today? What did I do differently during today's ride?

Pulled the caliper and checked the slide pins, they seem to be fine.

Bled the rear brake, but I don't think this is a hydraulic issue as the piston does appear the retract when I let my foot off the pedal.

Signed, Baffled. :huh:

 

[Cormanus]

That doesn't sound good at all, Tink? What now? New pads and test ride?

 

[Lord Popgun]

Sounds like you were dragging the brake. I don't know why, but you are not the first to do so. He warped the rotor and it had to be replaced.
Cormanus, Checking the rotor runout would be first on my list.

 

[TINK_imp]

That doesn't sound good at all, Tink? What now? New pads and test ride?

Yep, replace the pads and see what happens. Worst case I but a rotor too $$$ :-(

 

[Lord Popgun]

Tink, FYI if you don't have a manual, rear runout spec is 0.30mm or 0.012in

 

[Pterodactyl_imp]

As Popgun says, check rotor runout and thickness. The latter should not be a problem but have a look any way. That just ensures the rotor is still good. Blueing in itself is not a problem and the rotors will not be "cooked". A light skim or sand may be necessary if glazing or deep grooving exists.

Next step is to troubleshoot the problem. I quote directly from the '13 service manual:

Brake drags
~ Contaminated brake disc/pad
~ Misaligned wheel
~ Badly worn brake pad/disk
~ Warped/deformed brake disk
~ Caliper not sliding properly
~ Sticking caliper piston
~ Clogged/restricted fluid passage.


I don't know if your mechanical skill is equal to your undoubted photographic skill, but, if so, none of the above procedures or checks will be challenging. You have already indicated in your post that you are capable of all the above. A manual is useful however torque settings, caliper limits and other tips can be sought from forum members.

From your initial inspection you indicated that the hydraulics looked OK and the piston retracted. I would suggest that in checking the piston you pull the caliper apart and check for scoring (or "ringing") and that it is in round with the cylinder ID and piston OD within limits. Very light scoring can be removed by rubbing with fine (1200) wet and dry. Replace all the seals and lubricate both the piston seal and piston with Dot4 before assembly. There is some silicone grease points that need attending to so the assembly doesn't bind.

If the caliper is in good knick then it is back to the hydraulics. First check the pedal and linkage is completely free from any binding. Next step is master cylinder strip and inspection.

And so it goes. Plenty of advice from the forum to help. It is highly unlikely you have been riding the brake pedal, but if your not sure then, when all is back together, be careful.

Cheers and good luck.

 

[TINK_imp]

Today's update :exclamation:

The heat had warped the steel backing plates on the brake pads thus holding pressure on the rotor after the piston retracted.

This of course kept heating up the rotor as I rode.

Still have no clue as to what the root cause of the initial over heating episode was, but once the steel plates were warped the damage continued.




Rotor run out was right at the .008" spec.
Managed to tweak it back to .004"
Time will tell (after several heat cycles) if the tweak will hold.



Waiting on new pads to arrive.

Stay tuned... :biker:

 

[LongRanger_imp]

Yikes.

 

[Elipten_imp]

Wow never seen that before

Check the pads release before next ride


Sent from my iPhone using Tapatalk

 

[kmoney_imp]

That's a crazy amount of heat. I've never seen a backing plate rainbow before.

 

[mattmcuomo@yahoo.com]

That happened on my st1100. Rotor was glowing red! Had to release pressure to release the brake pads from rotor. Flushed line and rebuilt caliper, New pads and good to go.

Sent from me......

 

[Lord Popgun]

Tink, the 0.008 spec is for the front rotor. The .012 is for the rear. Looks like you are good to me. And no, I don't know why it is different

 

[TINK_imp]

Well, new rear pads are on and brake fluid changed.
It seems like all is good now... but it still feels to me that there's some drag...
I'll take her for a long ride tomorrow to assure the rear brake is happy now.

Here are the overheated rear pads:

 

[Cormanus]

Good luck Tink. Hope all's well.

 

[Pterodactyl_imp]

Tink, my advice would be to do some trouble shooting before your ride. At least flush the hydraulic system with new fluid and check the pedal for binding. The rotor may not take too well to another overheat.

Cheers and good luck.
Sorry, I see you have flushed the system. Once again, good luck.

 

[TINK_imp]

So far, so good.

Went for a 100 ride today to Crystal Lake Cafe and back. Rear brake is functioning fine, no excess heating. :biker:

Made darn sure my big foot was not resting on the brake pedal. Think I dodged a $$$ bullet this time. Still no clue as to why this happened, I'll assume "BIG FOOT" did it.

 

[the Ferret]

Well, hope you got the mystery solved Tink and it was self inflicted rather than a mechanical issue. Funny when I test rode my brothers new Triumph T 120 I noticed the brake pedal was a lot further in from my foot,. Since he was riding my CB 1100, I quickly told him thru our intercom to keep his clod hopper boot off my brake pedal that some guys on the forum were having trouble with that.

 

[rboe]

I did it to TWO discs, warped them good, but didn't damage the pucks. If you look at the photo where the edge of the disc is visible, you can see the edge is a grey colour. Originally it was painted black. Cooked right off (and in your case, things went a bit over board).

The main cause seems to be over sized Sidi adventure boots. Wearing my Tour Master boots does not lend its' self to riding the brake pedal. But I like the Sidi's much better so I took a big pipe wrench and bent the brake pedal in a few degrees (in my ever so humble opinion :angel: I think it sticks out too much, much more than my other two bikes which does not help matters). Since I bent the pedal in this has not been a problem at all.

 

[TINK_imp]

I did it to TWO discs, warped them good, but didn't damage the pucks. If you look at the photo where the edge of the disc is visible, you can see the edge is a grey colour. Originally it was painted black. Cooked right off (and in your case, things went a bit over board).

The main cause seems to be over sized Sidi adventure boots. Wearing my Tour Master boots does not lend its' self to riding the brake pedal. But I like the Sidi's much better so I took a big pipe wrench and bent the brake pedal in a few degrees (in my ever so humble opinion :angel: I think it sticks out too much, much more than my other two bikes which does not help matters). Since I bent the pedal in this has not been a problem at all.

BIG FOOT found!

You were on the right track, Rboe. My Aerostich Combat Touring boots (made by Sidi) were the ones I had on when I found myself OVER covering the brake pedal.

Today I caught BIG FOOT red handed... as I was exiting the freeway I was working my way through some heavy mall traffic when I pulled in the clutch to downshift the bike lunged forward... your guessed it, I had my foot on the brake pedal applying pressure to the brakes without realizing it.

When I got home I adjusted the rear brake pedal position as low as it would go. After a quick test ride I could tell right away I liked the new position better, and hopefully BIG FOOT will not return.

Oh, and I have some Alpinestar touring boots that I'll wear from now on when I take the CB1100 out. :biker:

 

[dwcurton_imp]

This seems to be common. The same issue surfaced with my V-Strom when I first got it. Riding with regular shoes on, no problem. Put on my steel-toed work boots, problem. I didn't cook the rear brakes, but noticed the bike acted like it was pulling an anchor and every time I pulled the clutch in to shift, the bike dove down. Problem was the larger boot engaged the rear brake.

So now I test every time I have a new boot or bike. I adjust the brake lever down as far as I can and try to train myself not to rest my toe on the brake when riding.

Glad you found it. Experience is the best teacher.

Don