Seized ST1100 rear brake

Zider drinker

Zider drinker

Joined
May 5, 2024
Messages
12
Age
60
Location
Somerset UK
Pan has been out on drive for sometime and,though covered,the rear brake has seized.I obviously need to unseize it but don't want to damage it in the process.Any ideas beyond WD40?
 
I'm not familiar with the 1100 but I believe you do not have the Secondary Master Cylinder. It would help if you post the year and if it is ABS or not. Not knowing, I'd open the rear caliper bleed nipples to relieve pressure. If the wheel unlocks, then you have a return port blocked in the brake system. If it is still locked, then the caliper is frozen on its pins (it should slide side to side as the pads wear). In this case you will need to remove the rear caliper, clean and lube the pins and probably clean the pistons as well. Corrosion does not heal by itself.

It is a good idea to keep WD40 away from the brake caliper!
 
Zider drinker said:
Pan has been out on drive for sometime and,though covered,the rear brake has seized.I obviously need to unseize it but don't want to damage it in the process.
Click to expand...
Definitely leave that WD40 can in the house...

I'd gentle pry the pads apart/pistons back just enough the caliper can be lifted off the rotor, preferable with a tool like this:

b1.96.95.10003009910FR10.JPG


drain the brake fluid with an appropriate bleeding tool and familiarize myself with removal of the caliper bracket and the methodical process of rebuilding the caliper (replace rings, possible pistons as well...)

Normally it should by possible to push the pistons in by hand force only (grab rotor with fingers, apply firm pressure on caliper with your thumbs); anything beyond that indicates that a rebuild is due...
 
SMSW said:
I'm not familiar with the 1100 but I believe you do not have the Secondary Master Cylinder. It would help if you post the year and if it is ABS or not. Not knowing, I'd open the rear caliper bleed nipples to relieve pressure. If the wheel unlocks, then you have a return port blocked in the brake system. If it is still locked, then the caliper is frozen on its pins (it should slide side to side as the pads wear). In this case you will need to remove the rear caliper, clean and lube the pins and probably clean the pistons as well. Corrosion does not heal by itself.

It is a good idea to keep WD40 away from the brake caliper!
Click to expand...
Thanks this helps
 
John OoSTerhuis said:
... Walmart not so much ($39).
Click to expand...
Beats scratches and possible other damage whilst attempting to pry a screwdriver or tire iron between rotor and pad...
Often there isn't enough space for any lever (like the rear brake on my GF's NT700VA, sandwiched between the not removable panniers)
 
Zider drinker said:
No not at all I'm starting now on working on it using tips I've had from members.
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I had that same problem a few months ago. I hooked up a hose to the bleeder and loosened it to relieve the pressure. I could then turn the wheel. You don’t have much room to work with if you remove the caliper only as it won’t clear the disk. Maybe you know this already; you can remove the bolt holding the caliper assembly to the swing arm without taking the wheel off or completely removing the axle. Just enough to clear the bracket.
Support the rear wheel with pieces of wood or shims. Someone here suggested an inflatable bladder which is great.
https://cdn.thewirecutter.com/wp-co...1.png?width=786&quality=75&crop=2:1&auto=webp

Be careful not to lose the collar.
Once free of the disk you can service the caliper with that tool suggested or use a C clamp. Make sure you clean the pistons before forcing them in. Use a shoelace with brake fluid and use a figure 8 type rotation to get the dirt and grime out.
The problem is usually the squared O ring that gets corrosion behind it and ends up squeezing the piston instead of allowing to rest just shy of the disk surface.
 
Sunday Rider said:
I had that same problem a few months ago. I hooked up a hose to the bleeder and loosened it to relieve the pressure. I could then turn the wheel. You don’t have much room to work with if you remove the caliper only as it won’t clear the disk. Maybe you know this already; you can remove the bolt holding the caliper assembly to the swing arm without taking the wheel off or completely removing the axle. Just enough to clear the bracket.
Support the rear wheel with pieces of wood or shims. Someone here suggested an inflatable bladder which is great.
https://cdn.thewirecutter.com/wp-co...1.png?width=786&quality=75&crop=2:1&auto=webp

Be careful not to lose the collar.
Once free of the disk you can service the caliper with that tool suggested or use a C clamp. Make sure you clean the pistons before forcing them in. Use a shoelace with brake fluid and use a figure 8 type rotation to get the dirt and grime out.
The problem is usually the squared O ring that gets corrosion behind it and ends up squeezing the piston instead of allowing to rest just shy of the disk surface.
Click to expand...
 
Once having it out and on the bench most here manage to drive the pistons out the caliper with compressed air...
Really bad cases might require a short hose and old brake master cylinder attached to force it out...
(once worked on an old CX500 Eurosport where even this failed, but several cycles in the 60°C ultrasonic cleaner finally freed them in the end...
good that I held the caliper in an old backing-tray with a rag over it, quite a mess when they finally 'banged' out... ;) )
Insert a stack of wooden strips (or very dense cardboard), this will not only prevent them from flying across the shop, the already loose piston can rest on them while the other one gets driven/pumped out equally, remove the strips one by one...

Dental pick for removing the old rings, and gentle cleaning crud and crystals out the grooves...
Cleaning the pistons with a mild abrasive fleece, but replace if any scratch-marks or pitting corrosion is noted...

If you go OEM or aftermarket for the spares is a personal decision... there kits with stainless steel pistons offered on eBay...
 
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