Rear wheel binding

Please report back when you know. I've been watching this thread carefully as I have similar issues on a new-to-me 2006 and I'm repairing it vicariously through this thread, and desperately trying to not start a new thread on my issue :)
 
Thanks. I'm still in the disassemble/inspect stage and I'm not certain my issue is any different than the OP (basically its rear brake drag - I suspect SMC, but am going to clean up rear caliper pistons first) so I'll get deeper in, clean and inspect, and if my issue is significantly different I'll start a new thread.
 
Sorry, but it has been raining hard all day here in NC. The bike is still too new to me and sparkling clean for me to justify taking it out. Tomorrow's forcecast looks better and I'll be sure to report back.
 
jfheath said:
What Crusty Said. The fluid pressure has a long way to go and has two tiny compensation ports to pass through. One in the SMC, one in the rear master cylinder reservoir.
Personally, I prefer to ensure that the fluid returns as it should. See-sawing while keeping the pressure on both pistons helps to push them in further a bit at a time. Don't know why it should, but it seems to.
Make sure the SMC plunger is extended.
Make sure you have enough room in the rear fluid reservoir to accept the returning fluid.
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Worked like a charm. Thanks!
 
CruSTy said:
You should be able to push them both in at the same time though there will be more resistance than moving just one. If you cant push them both together that could be an indication that the Secondary master cylinder (at the front left caliper) return port is clogged, corroded or mis-adjusted not allowing the brake fluid to return to the master cylinder. You can relieve the pressure by opening the rear bleeder on the rear caliper to see if the pistons will retract far enough to insert the pads but you may find once you apply the rear brake via the SMC it may cause the dragging to return.
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Thanks very much. Testing out on the road tomorrow!
 
Dang it. Pads are still clinging to rotor after all that work. Rotor very hot after a 5 minute drive.

What do you think I should do next?

 

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Dr. Kauz said:
What do you think I should do next?
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Before you do anything else open the rear bleeder on the rear caliper to relieve any pressure that might be applied to the pistons. Check wheel rotation. If it is still dragging something is still assembled incorrectly. If the wheel rotates freely after relieving the pressure the SMC is likely the culprit. I see in the picture above the inside pad has been dragging on the rotor hub. Is that from a previous pad assembly error? (happened to me once) Does the rear brake make the same noise as in the initial video? Before installing pads did you check to be sure the caliper is floating freely on the caliper slide bolts? You can remove the rear pad quide pin and remove both pads while the caliper is in place to check this. Can't tell from the photo but the caliper appears to be slightly askew. Could be an indication that the slide bolt(s) are cross threaded. Pay close attention to #14. It can easily be cross threaded into the caliper. You should be able to thread 99% in just using fingers.
 

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CruSTy said:
Before you do anything else open the rear bleeder on the rear caliper to relieve any pressure that might be applied to the pistons. Check wheel rotation. If it is still dragging something is still assembled incorrectly. If the wheel rotates freely after relieving the pressure the SMC is likely the culprit. I see in the picture above the inside pad has been dragging on the rotor hub. Is that from a previous pad assembly error? (happened to me once) Does the rear brake make the same noise as in the initial video? Before installing pads did you check to be sure the caliper is floating freely on the caliper slide bolts? You can remove the rear pad quide pin and remove both pads while the caliper is in place to check this. Can't tell from the photo but the caliper appears to be slightly askew. Could be an indication that the slide bolt(s) are cross threaded. Pay close attention to #14. It can easily be cross threaded into the caliper. You should be able to thread 99% in just using fingers.
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Bled and no change in tire rotation. Still super hard to move. Pad pin threads seem good but it may be a little bent. I'm going to order a new one. The caliper slides okay. The marks on the rotor have gotten worse since I started messing with it all but they were there in lighter form when I bought the bike. No scraping noise anymore. Other than replacing the pin what would be your advice?
 
Dr. Kauz said:
Other than replacing the pin what would be your advice?
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That pin is hardened and not likely bent. The bolt being cross threaded in the caliper is more likely the cause. The thread will need to be repaired or the caliper replaced if that is the case. I have straightened out the threads in the caliper using a little trick. Take the caliper loose from the mounting. You can leave the hydraulics connected but the caliper slides need to come off. Using the existing bolt #14 examine the threads on the bolt so see if they are damaged. They will probably be fine. using that bolt insert it into its thread FROM THE OPPOSITE SIDE OF THE HOLE. If there are any straight threads left they will be there. Carefully start the bolt from the backside watching to keep it aligned (centered) in the hole. Slowly run it in as far as you can get it. It may feel tight as you straighten the thread. Remove the bolt and examine the threads in the caliper to see if any material has been removed. If the thread appears ok then install the bolt from the normal side to see that it threads easily. This could be done with the proper sized tap but a tap will remove material so try using only the bolt first. If that works reinstall the caliper without the pads and see that the caliper floats on the sliders easily. Reinstall the pads insuring the front edge of the pad fits into the slot. Pull the rear of the pads up against the spring and insert the guide pin for the pads. Best of luck.
 
jfheath said:
Strewth.

Well we are back to square one then. Time to go back and check everything mentioned so far, see if something has been missed. There are a lot of things that we (as remote observers) don't have answers to so its difficult for us to tell. We started off with a video of something scraping. This has to be a mechanical issue and that has to be the first thing to sort out, I would have thought if it hasn't already been identified.

I don't think we yet have answers to the following:

1) Did you change the rear caliper pistons seals ? (The pistons may be incapable of returning)
2) Did you verify that when the pads are out, you have a full range of movement of the caliper sliding into the wheel and away from the wheel ?
3) At one point you said that there was no room on the inside of the rotor to fit pads in. Was that problem solved ? What was the problem ?
4) Did you verify that the two slider pins were not bent ?
5) Did you check the caliper spring and those little tags ?
6) Did you find the source of the noise in the video ? What was it ?
7) Were you able to find out which brake pads are actually grabbing the disc rotor - or is it all three. The answer matters.

There are a few tests that you can make to find out if fluid is getting through the system properly. But the mechanical stuff is more important for, so I'll leave that for now.

One thing that is worth checking is whether the front left caliper is binding. Pump the front lever hard a few times. Check that the front wheel spins freely. If it doesn't then that may well be the problem as it will activate the SMC and keep applying the rear brakes.

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Regarding the slider pins - I posted this image for Fawlty a couple of weeks ago. It's the same image that CruSty posted, but I find that diagram from the microfiches a tad misleading - on the original, the slider pin #14 appears to be labelled as going through the red hole to its left. It doesn't - it screws into the threads in the hole I have coloured green and slides into the #16 boot. I've coloured the mating parts green or red.

View attachment 233047
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Yes, I agree.

1) Did you change the rear caliper pistons seals ? (The pistons may be incapable of returning)
I haven't done this.

2) Did you verify that when the pads are out, you have a full range of movement of the caliper sliding into the wheel and away from the wheel ?
Yes but it seems like it should slide easier.

3) At one point you said that there was no room on the inside of the rotor to fit pads in. Was that problem solved ? What was the problem ?
Yes, I was trying to figure out how to push the pistons in when it dawned on me. Just needed to work the pistons as a couple of people pointed out.
4) Did you verify that the two slider pins were not bent ?
I'll do this tomorrow.
5) Did you check the caliper spring and those little tags ?
I did, several times. Still can't always be sure how well the outside tab fits into the retainer.
6) Did you find the source of the noise in the video ? What was it ?
Yes, the retaining clip.
7) Were you able to find out which brake pads are actually grabbing the disc rotor - or is it all three. The answer matters.
I'll recheck this.

Thanks for the thorough advice and questions.
 
jfheath said:
Where exactly are the scrape marks on the rotor ?
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This was from an earlier post.Likely caused by a partially installed inner pad.
Also worth noting. The inner pad has a gap at the bottom an outer pas has a gap at the top of the rotor. This likely indicates the caliper is askew. That's why I suspect the cross threaded front pin bolt. I have seen and repaired this problem for another ST owner.

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Husoi said:
That sounds like the caliper..
try pressing the pdeal a few times and see if it gets better.
Isn't clear but at first view the pads look too close to the disk, do they need changing?
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Remove caliper and check pistons. THey get a lot of brake dust and road grime . Depending on age, may need to rebuild. I would clean as good as possible then bleed the brake system.
 
When you had these aftermarket rear pads removed,,, did they exhibit tapered wear of the brake lining ?? It looks like the top of the inboard pad is thinner than the bottom,,, but perhaps that is just due to the angled perspective of the camera. A taper would be evidence of caliper misalignment,, as John mentioned. That misalignment could also cause piston binding. Also, the pistons seem to be much extended for the amount of apparent wear on the aftermarket pads.

The previous owners of my bike took all kinds of shortcuts, that affected the systems functionality. It took quite some time to sort it all out,,, but that certainly can be done,,,, Cheers, Cat'
 
Wish you're in Texas close to me ... I'd ride over to put another pair of eyes and hands on this.

You include 2 still shots a few posts previous. And a video early on, which I paused and took screenshots, but the angle is rwong.

Can you do this ... take a photo or two at a level between the caliper and the axle, and so the photo includes the caliper, showing both pads, AND includes the axle and the spacer.

You want the camera straight on so the rotor appears flat (so we cant see its left or right surface)
 
Got to spend a few hours on this. I opened up the front slider bolt pin and the inner threads look bad in that some metal looks freshly milled. The bolt doesn't screw into the hole with finger torque for more than 2 turns. The bolt threads are fine. Tried putting the bolt in the other way and stopped after a few turns as it got tight. More shaved metal. Didn't want to force it. I also notice the old inner brake pad was worn a lot toward the rear but not at front of pad. I suppose I can't fix the inner threads. Should I be looking for a whole new caliper?
 
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