rear brake still dragging???

[Diamond Dave]

I just got my bike back home after having it at the dealer for the last three months getting repairs done on the sticking problem. They replaced the pads,SMC,PCV,rear caliper and then the pads a second time with OEM pads.After the six mile ride home the rear disc was too hot to touch while the fronts weren't even warm.Could this be normal because of the new rear pads.

 

[Igofar]

Sounds like they replaced the SMC, PCV and the pads etc. But I don't hear any mention of checking, cleaning or replacing the front pads. If the front pads are dirty or sticking, it can also cause the rear to drag. There have been so many recent cases of incorrect brake bleeding done by various shops & folks, I'm wondering if your system was bled correctly, using the OEM service manual procedure, or if someone attempted to use shortcuts in bleeding. This would also cause alot of your problems. I'd ask the mechanic or service manager how the brakes were bled. Alot of the shops don't follow the service manual's procedure, as it takes too much time, its a pain to remove all the plastic, ties up our mechanics too long, etc. I'd start by removing ALL the pads, cleaning all the pistons, lubing all the pins, and making sure there is no scaring on the pin causing it to bind, then Flush and Bleed the entire system using a motion pro bleed tool. They probably used a mity vac type bleeder and there is probably still air in your system as well.
Good luck.

 

[treemuncher]

I fought the same problems for some time. Once the SMC and the calipers were working freely, it all came down to bleeding the system properly.

For me, the Mighty Vac alone was not enough to get all of the air out. When I combined traditional "pump & hold pressure" techniques with the MV, then I finally got everything to work correctly. I bet I also went through nearly a quart of fluid to get it done 100% air free.

If I am not riding hard, I can usually hold my hand to the rear rotor after stopping. There is almost no drag (other than the driveshaft) when the system is working correctly.

 

[Mellow]

Here's another option... is it possible brake fluid was added during the time the pads were worn and now there is just a little too much in the system with the thicker new pads?

 

[Tom Mac 04a]

Though I normally find the rear disc is a higher temp than the fronts, it falls to the quick touch method. ( do carefully ! )
Pain starts at about 112f ( nasa tests )
if you can leave your finger on it for 1 sec. its about 160-180f which is max contact time before damage
if you can touch it for a few seconds, its more in the range of less than 120f
If you can hold the finger for 5+ seconds and longer its around or less than the pain threshold of 112f

So tho I find my rear disc is usu feels twice at hot at the fronts, it still passes the touch test so its prob normal....If you can't touch them at all like mentioned (while front cool )there is a def problem.

A quick check of the SMC function has been posted a few times; lay on floor, spin rear tire, push on SMC up/forward..tire should stop. release SMC, tire should spin again.

I would think that the fronts dragging just a bit enough to keep pressure on the rear via the SMC which require a check/cleaning of front pistons or as mentioned, a good proper bleed is in order

 

[Igofar]

Here's another option... is it possible brake fluid was added during the time the pads were worn and now there is just a little too much in the system with the thicker new pads?

Good point Mellow

 

[Diamond Dave]

if you can leave your finger on it for 1 sec. its about 160-180f which is max contact time before damage
if you can touch it for a few seconds, its more in the range of less than 120f
If you can hold the finger for 5+ seconds and longer its around or less than the pain threshold of 112f

If I use the above timetable I could only touch the disc for 1 sec. after the six mile ride.Then I went out again for maybe 3/4 of a mile and the rear was warmer than the front but not as bad.

 

[Tom Mac 04a]

I could only touch the disc for 1 sec. after the six mile ride.Then I went out again for maybe 3/4 of a mile and the rear was warmer than the front but not as bad.

If you held for one second, the rear at 160+degrees isn't that hot.... take a feel of you car discs and see what warm is ( or touch the pipes ! )

As I said, I've ALWAYS found the rear to be much warmer than than the fronts, but not to the point it's sticking. ( usu feels about 2x as warm/hot ).
It may not mean the disc is sticking if it passes the SMC test, just that maybe you favor using the rear a bit and its one disc as compared to the two fronts. Everyone rides a bit diff.

 

[Diamond Dave]

It may not mean the disc is sticking if it passes the SMC test, just that maybe you favor using the rear a bit and its one disc as compared to the two fronts. Everyone rides a bit diff.

It definitly passes the SMC test. I will ride a little bit more to decide if everything is ok

As always thank you everybody for all the feedback !

 

[Igofar]

I've listened to a member who had the same problem...Rear brake gets so hot he couldn't touch it. I checked the SMC..passed the test. We went for a ride. I followed him...I wondered why he was riding with his foot on the rear brake the whole time.
New boots, didn't have a clue, problem solved :bow1:
Check to make sure your footwear isn't resting on the side or edge of the rear brake lever.

 

[Diamond Dave]

Check to make sure your footwear isn't resting on the side or edge of the rear brake lever

Its a possibility I have size 12Ds.

 

[jfheath]

Check to make sure your footwear isn't resting on the side or edge of the rear brake lever.

Oh, I do hope that is the answer ! A nice bit of lateral thinking, sir.

If not, consider temporarily removing the white heat shield layer from between the brake pad backing plate and the thin metal anti squeal plate. If the pads are new, this extra thickness can sometimes be too much, preventing the pads from moving away from the disk, causing heat build up. Removing the pad provides a bit of space for the pads to move away from the disc.

While you have the pads out, make sure the caliper can slide back and forth. It takes a little push-pull effort, but they should move reasonably easily..

Do this on the front too if the pads are new, as they may be dragging, causing the back brake to be applied. I know that if the front pads drag that there should be some heat build up, but i once spent days trying to sort out the hot back brake problem, concentrating on the rear, only to find the cause was the new front pads I had fitted. And the front discs were not hot.

There is no point removing the heat shields if the pads are already well bedded in.

Also check that that the fluid reservoirs are not over full. If there is no airspace, the pads will have some trouble releasing their grip.

 

[Tom Mac 04a]

New boots, didn't have a clue, problem solved

I guess that right up there with the toes dragging in a turn ( cause yr not on the balls of the foot re peg )

 

[Igofar]

I guess that right up there with the toes dragging in a turn ( cause yr not on the balls of the foot re peg )

And I thought the road was just reaching up and grabbing my foot