Intermittant RR brake drag

Well here we go again. Just changed the tires to get ready for a trip. When I put everything back together and took it for a spin the rear brake caliper was seizing the RR wheel rotor and it was getting mighty hot.

I checked everything, took everything back apart and double checked everything. The caliper bracket is moving in and out like a trombone, so that is not it.

I say intermittent because I can get it to break free if I simultaneously pump the front and rear brake lever and pedal at the same time then the RR wheel breaks free somewhat and will coast down the road and I can push the bike backwards with minimal force. When I ride for a while it comes creeps back.

Before the tire change I was having no problems at all.

Any ideas would be appreciated.

Thanks.

I am unable to type much do to hand surgery, however, if you PM me a contact number I will try to assist you.
Igofar

PM sent

Now that the bike has cooled the rear wheel spins freely??

ST-Traveler said:

PM sent

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+1 Wise choice. :bow1:

After talking with Igofar we have decided it is the SMC starting to fail. I have the parts ordered and should be in next Wed or Thursday.

Thanks Larry for the advice and trouble shooting the problem.
FWIW when I cycled the SMC in and out the rear wheel really free'd up and spun quit easily. This was an indicator that indeed the SMC is starting to fail and or going bad.

Once the parts arrive and are installed I will update this thread with the results.
Fingers crossed at this point and the trip has been cancelled.

This morning I went out to the bike and spun the rear tire - Cold- and it spun very freely with little effort, while spinning the rear wheel I applied the rear brake pedal and it stopped and the wheel was then locked up. I went to the SMC and cycled it by hand and with out doing anything else the rear wheel spun freely again.
This I believe is a signal of SMC going bad and having intermittent wheel lock up.
I recommend to my fellow ST riders to check this component for failure every so often. My bike has almost 113,000 miles before this failure showed up.

I am glad I caught this when I did instead of being a thousand miles from home.

jfheath said:

It might be handy to know that if the SMC fails (by blocking off the relief port due to internal crud and corrosion), then the rear wheel locking scenario can be temporarily rescued with the aid of a brake hose clamp.

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Preventive maintenance servicing is certainly the best medicine but it might not be a bad idea to have a clamp in the toolkit JIC. There has been more than one mention here about someone being stranded by this very gremlin.

A quick Google for brake hose clamps turned up a thread or two warning of irreparable damage to brake hoses. Is this (as the kids say) a thing? If caught in that predicament is the brake hose then replaced straightaway?

ST Gui said:

A quick Google for brake hose clamps turned up a thread or two warning of irreparable damage to brake hoses.

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Another option is to bleed the rear and live with what is left on the front (which is till pretty good) until repair.

Or rig up a spacer between FL caliper and SMC to prevent activation of the SMC.

ST Gui said:

A quick Google for brake hose clamps turned up a thread or two warning of irreparable damage to brake hoses. Is this (as the kids say) a thing? If caught in that predicament is the brake hose then replaced straightaway?

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If I'm a thousand miles from home or 100 and I'm being self sufficient, clamping a hose and destroying it is better then walking. Spend a few hours on the side of the road waiting for help or replace a $30 hose later?

T_C said:

If I'm a thousand miles from home or 100 and I'm being self sufficient, clamping a hose and destroying it is better then walking. Spend a few hours on the side of the road waiting for help or replace a $30 hose later?

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All that's a given as in that never was in question and doesn't answer my question. I'll make it clearer: does this do permanent damage to the brake hose? Simple.

I'd hate to be in that position in the first place but it would be just as bad to believe once the SMC is repaired the hose is OK if it's not. To put it another way: do I ride into the OCD Garage with or without a new hose?

MidLife said:

Or rig up a spacer between FL caliper and SMC to prevent activation of the SMC.

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Thanks for the reminder! That was mentioned somewhere here before and might just be the hot tip: a suitable spacer zipped-tied in place. Obviously we'd want regular preventative maintenance to preclude such an event.

You will need to replaced the hose you damaged.

ST Gui said:

All that's a given as in that never was in question and doesn't answer my question. I'll make it clearer: does this do permanent damage to the brake hose? Simple.

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As Larry has already said, yes. Crushing the hose, then forcing the brake fluid to pool at the point of the crush, will inevitably cause some fatigue. It may not fail right after removing the clamp, but it will have certainly weakened it and will be the first point of failure in due time.

Think of it as using a tourniquet in first aid. Can save a life, or a ride, but there is a price to be paid later.

T_C very well said, thanks for your input.
What is really scary....I have replaced at least two rear brake lines on new model ST's after having been serviced for recalls where the shops technician clamped the rear line with what appeared to have been needle nose vice grips, the lines were still dented and even had teeth marks in them!
A sign of the time shop shortcut I guess.
Want a real answer? Contact any brake line company and ask them if their lines should ever be clamped for any reason, and will it damage the line?

ST Gui said:

......a suitable spacer zipped-tied in place....

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Even easier to jam a small spacer in place if you've implemented the Ltimb mod.

MidLife said:

Even easier to jam a small spacer in place if you've implemented the Ltimb mod.

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Yeah no. I've never noticed the clunk and a spacer would only be an emergency stop-gap measure.

If I were to do that mod (which I wouldn't) I'd just swap out that ball-point pen srpring for a valve spring or cut down clutch spring.

Igofar said:

Want a real answer?

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Nah I come here to listen to everybody swap lies and bench race tales.

After doing some more reading on this issue, I wanted to throw in some more info. When the rear wheel brake was dragging I happened to get off the bike and check both front rotors as well. I noticed and thought it was odd that the right front rotor was warm to the touch but the left front rotor was cool to the touch. I got puzzled when I did this test and was not sure what to make of it. possible the left front rotor is not grabbing either. I am still waiting on parts for the SMC replacement but wanted to through this observation in as well.

I have a 2009 ST 1300 I bought new in December of 2012. My R/F rotor is always warmer than the L/F rotor and the R/F pads always wear faster than the L/F pads. I have no brake issues that I know of, there is nothing sticking and everything moves very freely and I have tested my SMC and it works fine and there is no dragging whatsoever at the rear wheel- I have never determined a reason for this either.

OK so I got an 04 that had the rear brake dragging prior owner rebuilt the rear caliper and replaced the SMC still dragging though so finally this past weekend I replaced the PCV and bled the system again and low and behold its fixed.

ST-Traveler said:

This morning I went out to the bike spun the rear tire - Cold- and it spun very freely with little effort, while spinning the rear wheel I applied the rear brake pedal and it stopped and the wheel was then locked up. I went to the SMC and cycled it by hand and with out doing anything else the rear wheel spun freely again.
This I believe is a signal of SMC going bad and having intermittent wheel lock up.
I recommend to my fellow ST riders to check this component for failure every so often. My bike has almost 113,000 miles before this failure showed up.

I am glad I caught this when I did instead of being a thousand miles from home.

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One question I have about this thread, what do you mean by RR brake? My ST only has one rear rotor, on the left side of the wheel. Are you referring to the right side (inside) brake pad? I don't know how you could tell whether it's the inside or outside pad that is dragging, but that's beside the point anyway, I think. A point that I fail to understand is why the SMC valve is a suspect. If the rear wheel locked up when you spun the wheel and applied the rear brake, the SMC would not be a factor, since it won't be engaged if the bike is stationary when the brakes are applied, either front and/or rear. I would suspect another problem, perhaps the PCV valve, as someone else has suggested (ref. post 21 above).

Don in my case I have an 03 and an 04 on my 03 the rear brake locked up when I used the rear brake pedal while in motion as you said in that case the SMC fixed my problem on the 04 the prior owner a good friend of mine replaced the SMC and rebuilt the rear caliper it didn't fix the problem I replaced the rear master cylinder and that didn't fix it I sourced a PCV and replaced it and that fixed the issue on the 04. I think the OP manually worked his SMC to see what was happening.