Rear brake seizing on.

[Homer62]

Hi everyone,
decided to change all brake pads, but now the rear brake locks on after using the brake for a short time. Pistons went in with hand pressure, it’s the 1100 with cbs, any ideas what could be wrong? Thanks in advance.

 

[John OoSTerhuis]

Check the caliper slider pins for corrosion. Also, the new pads may have displaced fluid and overfilled the reservoir.

 

[Homer62]

Check the caliper slider pins for corrosion. Also, the new pads may have displaced fluid and overfilled the reservoir.

Will check caliper pins, thanks. Drained some fluid out, was at the upper level. Good advice.

 

[jfheath]

Also
If OEM pads, check you have the correct pair on the rear. They have a notch in the tab end, which matches the ridge in the chrome retainer which clips onto the caliper bracket.

Check that the front pads aren't binding slightly. This will cause the rear pads to drag.

Check the 3 hole caliper linkage behind the left hand shroud. It needs to be able to pivot freely. It has needle roller bearing in there. Out of sight, it is easy to forget about.

Have you attempted to fit the white heat shields that come with Oem rear pads, to the front pads? There isn't room. The front pads will drag, which with cbs causes the rear brake to be applied.

Have you checked the rear caliper slider pins ( different from the pin that keeps the pads in place). They need to be smooth and shiny, and the rubber boots need to be intact and properly seated in the caliper and bracket ( one on each ). They need a smear of rubber or silicone grease. Dont put too much grease on the caliper slider pins. A lot will cause air pressure to move the pads towards the brake disc.

Make sure the pad springs are the correct way round. Wider strip closest to the pistons. Also check the inside pad is on the correct side of the two small tags that stick up on the narrow strip.

Search ST1300 articles for 'Avoiding the Pitfalls'. Yes I know you have an ST1100, but everything in that article applies to the ST1100 with combined braking, and the photos in there of the rear caliper are all relevant. The only significant difference is in the design of the SMC, which on the 1100 is a separate unit, downward facing which rarely suffers the same problems as the 1300 design. The rear caliper is a very similar design on the 1100 and 1300.

Fluid up to the max fill line is correct for new pads. Brim full is too much. If you have fluid below the max line when the pads are new, you run the risk of it being emptied as the pads wear down.

 

[Rob20111]

Make sure you tighten the caliper stopper bolt (I think that's what it's called) BEFORE you tighten the axle bolt and pinch bolts.
This allows the caliper to be aligned properly.

 

[Homer62]

Jfheath,
thanks so much for that article, looks like I’ve caused the problem by pushing both outer pistons at the same time, I’m not hydraulically minded so I think the bike will need uplifted and delivered to my garage repair guy a few miles away. Thanks for all help received.

 

[SMSW]

Did you do a complete flush of the brake system with new fluid? From your description I'd guess not, and from what I have read here, bad brake juice seems to be the cause of a lot of our brake problems. Brake fluid is hygroscopic, it absorbs moisture from the atmosphere and deteriorates. Folks have described ancient clutch and brake fluid that was dark and had 'gunk' in it. Anything other than clean, solids free fluid can clog small passages and corrode the insides of calipers and brake lines. I replaced all the calipers on one of my Guzzi's and while I've not heard of the same corrosion here being a frequent problem, at least one poster reported calipers that were beyond saving.

 

[Kevcules]

Jfheath,
thanks so much for that article, looks like I’ve caused the problem by pushing both outer pistons at the same time, I’m not hydraulically minded so I think the bike will need uplifted and delivered to my garage repair guy a few miles away. Thanks for all help received.

Myself and many others haven’t loosened the bleeder screw before compressing the pistons many many times without issues.
You’re fluid must be contaminated from lack of flushing. Give it a good thorough bleed and hopefully it gets back to normal.
Good luck

 

[jfheath]

You have to make sure that as you press one in, the other doesn't move out. I often press both in together, but if the bleed valves are closed, it can be quite difficult to get all of that fluid through two very tine compensation ports. And as Larry pointed out to me, with just one thumb, you run the risk of applying uneven pressure, cocking the piston slightly and making it harder still.
So I stop one moving with a piece of wood and press the other in by itself now.
If the bleed valve is open - no problem they should both push in very easily.

 

[Homer62]

Hi, thanks for all helpful advice, I’ve been away on holiday without the bike boohoo, finally had a chance to look at the brakes, decided I would check rear brake nipples to see if fluid was running free, turns out rear brake - front nipple fluid flowing out freely but rear brake - rear brake nipple no fluid coming out, my question is there a way I can fix myself or is it a garage job? Thanks in advance.

 

[mjc506]

It may be a blocked nipple, worth unscrewing it all the way, removing it, and checking (pipe cleaner ideally, but a bent paperclip will work). Don't be tempted to push a paperclip down it while still in the caliper, you might unblock it, but just push the crud back into the caliper (If the nipple is blocked with gunge, it may be worth removing the pistons as well and cleaning it out properly)

 

[Slydynbye]

Hi, thanks for all helpful advice, I’ve been away on holiday without the bike boohoo, finally had a chance to look at the brakes, decided I would check rear brake nipples to see if fluid was running free, turns out rear brake - front nipple fluid flowing out freely but rear brake - rear brake nipple no fluid coming out, my question is there a way I can fix myself or is it a garage job? Thanks in advance.

That is what I had. You will need to trace the point of resistance by opening lines along the path leading away from the caliper. USE THE PROPER FITTING WRENCH!
In my case it was a blocked proportional valve. I had to loosen the fitting going into and out of the unit to test flow.
Found the Valve blocking any fluid through it. Probably contaminated and clogged. Replaced it and Voila Brakes!

 

[Homer62]

first of all thanks to everyone for for all advice, here’s a bit of a puzzle, checking the brake pedal and brake hoses I came across a clamp that was stopping the fluid going to rear brake- rear nipple, took it off and fluid running free, bled the system and now my brakes are great, so why would someone stop the fluid? Could it be a partial bleed and left on by accident or did previous owner not want the cbs? Can anyone shed light on the clamp that was used.

 

[CYYJ]

...I came across a clamp that was stopping the fluid going to rear brake-

Wow, I think that discovery is a new one for all of us. I cannot imagine why someone would have put that clamp there.

Michael

 

[MidLife]

I came across a clamp that was stopping the fluid going to rear brake- rear nipple.....

Am not familiar with the 1100, but for the 1300, was thinking that maybe having such a clamp on hand might be helpful on the road in case of a rear seizing due to an SMC starting to act up.

In a "pinch", bleed the pressurized line and temporarily clamp it to get out to the nearest wrenching hand without the rotor turning red. Maybe this bike had a similar issue at one time.

You may want to keep the clamp in your pocket until you are absolutely sure all is good with your CBS.

 

[Andrew Shadow]

Those clamps are used to block off fluid lines (brake, fuel, etc.) when service is being done. They are used to temporarily stop the flow of fluid while the system is open, such as removing a caliper, so that it will not completely drain of all fluid and will require only a minor bleed from the point after the clamp.

Either service was being performed to the brake system downstream of where the clamp was installed and it was forgotten there, or it was intended to disable the system downstream of the clamp due to a system problem.

 

[jfheath]

Either service was being performed to the brake system downstream of where the clamp was installed and it was forgotten there, or it was intended to disable the system downstream of the clamp due to a system problem.

A friend had his service guy completely flummoxed by the ST1300s brake system, and couldn't understand why it was locking on. With the owners permission he clamped off the line to the rear outer pistons so that he could ride it away, and take it back another day. In the meantime the friend described his problem to me, and I gave him a copy of 'Avoiding the Pitfalls'. Apparently it was a revelation to the service guy, and it has been doing the rounds of the local service centres (he asked permission).