Relieving dragging rear brakes? (at least temporarily)

[sstakes1]

I believe I might have the dreaded SMC failure. I thought that the drag was increasing over the last month, but until last week the wheel would turn about a turn and a half, but make noises when stopping. Yesterday, about a mile from home, I could feel the rear brakes not releasing fully. Now the wheel won't even make a quarter turn.


I am deciding to take this into the shop as I may not have the time to fix this. However, is there anything that I can do to temporarily relieve the locked brake so that I can ride the bike in? I do not have a trailer. I would appreciate detailed directions as my technical abilities are not that high. I have removed and mounted the rear wheel several times though...

In addition, is there a way to confirm SMC failure? Any other major reasons why the bind may happen?

--Ram

 

[st1300r]

Lots of reasons which may include the SMC not releasing, fm clogging one of the lines, dry caliper slide, galled hangar pin, dirt/corrosion on the pistons. You mention hearing something though, how much life is left on the rear brake pads. They don't always wear evenly front to back. Outside shot but are you hearing metal to metal scrapping?

If you're stopped engage the front brake and pull back on the bars, does the noise then go away when you move?

 

[sstakes1]

how much life is left on the rear brake pads

They seem to have a decent bit of life on them (more than 50%)

Outside shot but are you hearing metal to metal scrapping?

No the noise is something like you would hear with a dusty drum brake. Does not sound like metal to metal

If you're stopped engage the front brake and pull back on the bars, does the noise then go away when you move?

Can you clarify pull back on the bars? do you mean try to roll bike backwards?

Thanks
--Ram

 

[st1300r]

Yup.
The smc rides on the left caliper so as you apply front brake it rotates forward a little with the disk putting pressure on the smc piston which then operates the two out rear pistons.

Just thinking out loud, but if you roll the bike back and apply front brake it might pull the smc piston back and relieve the pressure on the rear out pistons. If so it might mean the smc is the culprit.

 

[sstakes1]

Just thinking out loud, but if you roll the bike back and apply front brake it might pull the smc piston back and relieve the pressure on the rear out pistons. If so it might mean the smc is the culprit.

Ah I see. Thank you. Will try this when I get back to my home this evening.

Did you say it also actuates two out of three rear pistons? Perhaps I can confirm this visually as well.

--Ram

 

[rossilvr]

I have been trying to solve a break dragging problem for a year+. I feel like I am the guru of the ST break system with a break drag. I have taken everything apart at least 17 times with no result. You can read my threads as I dont want to bore people here

Few things you can do. You can drain the break fluid from the rear caliper bleed niples. Put a clear hose on them, open with a 8mm wrench and press the break pedal repeatedly. With no fluid in the system it wont drag unless you have a mechanical problem with the caliper - the pads dont slide easily, etc..

Or you can spread the pads with a large screwdriver so they dont touch the disk and drive to the mechanic without using the rear break - although the SMC will pump fluid in to the system eventually. But you will be ok for a few miles.

Or don`t do a thing. I have been riding my ST with th break drag for 25+K kilometres for season and a half (got through almost 4 pairs of pads). I go to the Alps in Austria and Italy, etc. I live with it because I couldnt fix it, my dealer couldnt fix and I have changed all the parts in the system you can think of.

Hope that helps

rossilvr

I believe I might have the dreaded SMC failure. I thought that the drag was increasing over the last month, but until last week the wheel would turn about a turn and a half, but make noises when stopping. Yesterday, about a mile from home, I could feel the rear brakes not releasing fully. Now the wheel won't even make a quarter turn.


I am deciding to take this into the shop as I may not have the time to fix this. However, is there anything that I can do to temporarily relieve the locked brake so that I can ride the bike in? I do not have a trailer. I would appreciate detailed directions as my technical abilities are not that high. I have removed and mounted the rear wheel several times though...

In addition, is there a way to confirm SMC failure? Any other major reasons why the bind may happen?

--Ram

 

[The Dan]

If the SMC is bad and you bull it back all that is going to happen is the push rod will slide back away from the piston. It will not disengage the SMC. Look at 21. http://www.powersportsplus.com/parts/search/Honda/Motorcycle/2005/ST1300+A/LEFT+FRONT+BRAKE+CALIPER/parts.html

 

[Anna'sDad]

Did you say it also actuates two out of three rear pistons? Perhaps I can confirm this visually as well.

The hydraulic brake system used on the ST1300 is linked, in that the front master cylinder operates both front and rear brakes, similarly the rear master cylinder also operates both front and rear brakes.

Here's a brief schematic that may aid in understanding the linked brake system.

 

[MidLife]

The two front outer pistons are HYDRAULICALLY completely isolated from the rest of the system. In a pinch, you can bleed the rear system and you are left with 2/3 of the breaking power on the front, with no interference form the rear. This would allow you to get to the shop in limp mode.

If your case is an SMC issue (other threads explain how you can find that out), some have found that a few heavy stomps on the pedal (while the bike is not moving) can help unstuck the SMC and release the rear brake....until next time you apply the brakes while moving!

I believe I might have the dreaded SMC failure. I thought that the drag was increasing over the last month, but until last week the wheel would turn about a turn and a half, but make noises when stopping. Yesterday, about a mile from home, I could feel the rear brakes not releasing fully. Now the wheel won't even make a quarter turn.


I am deciding to take this into the shop as I may not have the time to fix this. However, is there anything that I can do to temporarily relieve the locked brake so that I can ride the bike in? I do not have a trailer. I would appreciate detailed directions as my technical abilities are not that high. I have removed and mounted the rear wheel several times though...

In addition, is there a way to confirm SMC failure? Any other major reasons why the bind may happen?

--Ram

 

[sstakes1]

First off, I want to thank everyone for their responses. I finally got some time with the bike at home today. I just pushed on the rear caliper with my hands and it freed up the wheels. I think it rules out SMC. Am I right? I think it could be the case of a pistons or calipers and will follow the cleaning procedures for the rear calipers. Please let me know if I should try anything else.

I just noticed that the caliper body was wiggling a little bit. Perhaps this is contributing to the noise while braking. I will also check the torques on the bolt.
--Ram

 

[sstakes1]

I have done further experimentation after the kids were off to bed and here are the results.

With the bike on the stand and just the rear brake applied, the pads grab the rotor, but upon releasing the brake pedal, they do not tend back off from the rotor. I am able to push the caliper to release the rotor. I've seen some posts here that may indicate internal hose damage could be the cause of it, but the hoses look fine (externally at least). Any other suggestions other than cleaning out the calipers and pistons? If that fails, I will replace the hoses.

I posted earlier about a little wiggle of the caliper body. I have rechecked the torque and it looks okay. Can anyone please try the following for me and let me know the results? Hold the rear caliper body with the thumb and forefinger on either ends of the rear pin that holds the pads and move the caliper body side to side. Do you see any play? I see about 1-2mm of play there. Thanks in advance

--Ram

 

[Mellow]

I posted earlier about a little wiggle of the caliper body. I have rechecked the torque and it looks okay. Can anyone please try the following for me and let me know the results? Hold the rear caliper body with the thumb and forefinger on either ends of the rear pin that holds the pads and move the caliper body side to side. Do you see any play? I see about 1-2mm of play there. Thanks in advance

They're called 'floating' calipers and it's completely normal to have that play in them.

I would remove the wheel and clean the pistons and lube the pins that are on the bracket which they 'float' on and see if that works for you. Here's the article I did if it helps:
https://www.st-owners.com/forums/showthread.php?101206-ST1300-Rear-Brake-Piston-Cleaning