Brakes rebuilt but still binding on one side

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Aug 13, 2013
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Connemara, Ireland
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2000 ST 1100
My 2000 ST1100, non ABS had sticky brakes so new seals etc done. But the offside front is still sticking but only intermittently. I have noticed that there is some movement in the floating discs so wondering is it that.

All the other non ABS ones have not got floating front discs. Would this affect the problem
 
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All your disc brake calipers are 'floating'. If not, there's some binding issues or incorrect installation;). Make sure those caliper slider pins are clean and thinly coated with anti-sieze before assembly.
 
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thecivvie
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Connemara, Ireland
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2000 ST 1100
Both front disc are floating. I may just take them off and see what fixed one do. Pins look ok


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thecivvie
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Yeah pistons cleaned by the garage, I watched him do it. She us in the garage at the moment and was ok fir 2 days, they went to move her yesterday and the one side was solid


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thecivvie
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Thanks. Pistons have been cleaned twice in the garage so not sure. May try a second calliper and see if that cures it


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ST1100Y

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I have noticed that there is some movement in the floating discs so wondering is it that.
All the other non ABS ones have not got floating front discs.
Seems you've some (obscure?) aftermarket rotors/disks installed (pictures avail?), cause OEM all ST1100 rotors are fixed, only the callipers 'float'...

Anything that requires more then wiping with a rag is kinda 'obscure' when it comes to cleaning brake pistons... if their show corrosion/marks, I'd replace them.
Also not mentioned: did the mech carefully clean the grooves inside the callipers? Cause of their still filled with some goo/crystals the new rings will jam again...
(This task required quite some efforts when refurbing my '94 ST, I actually built my own scraping-tool to clear those grooves and checked with a small dentists-mirror...)

And while having the brakes apart anyway, its also procedure to clean & lube those 'float-pins' and the rubber boots (I've used ceramic paste).

Further: was a rep kit installed in the master-cylinder? Also regular procedure to do this anyway while rebuilding brakes...
 
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thecivvie
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Thought it had stopped but back with a vengance. And now it has changed sides !!!!! But the floating disc on that side, the bobbins are loose. I know as standard the ST1100 non ABS was supplied with a fixed disc not floating. Just wondering, if maybe both discs are warped? Is there a simple test that I can do before buying new discs and finding that is not the problem?
 

ST1100Y

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Thought it had stopped but back with a vengance. And now it has changed sides !!!!!
If the brakes are binding, its definitely within the callipers...
I'd get rebuild kits (while already at it anyway, also for the rear as well as both master cylinders...) including new pistons; I'm positive the brakes will then work like new/as advised again.

The shown after-market rotors might only contribute into that by being too thin, thus exposing too much of the calliper pistons, leading to contamination and corrosion there.
IIRC have OEM rotors a thickness of 4,8~5,2mm; 4,0mm is the absolute wear limit...
 
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thecivvie
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Will check the size of them. Putting the money together for a new set of discs anyway so will add the full rebuild kit to the list. It only happens every now and again. She can be parked up for a few days and it doesn't happen. Another day park up for 5 mins and locked solid
 
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Could the garage have cleaned them with spray brake cleaner? If so this may have caused the seals to swell.
 
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thecivvie
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I recall that when one side was rebuilt, if not both, the mechanic said that the seals had perished away. Nearly sure he said no seal at all. Would that have affected the pistons or calliper bores at all
 

ST1100Y

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"perished" seals would cause a massive leak, one would notice brake fluid squishing out when pressing the levers...
Over time the rubber can start to swell, causing increase of friction at the pistons, could even snip off rubber fragments which then jam in the clearance... pitting/corrosion/build up on the (exposed) cylinder walls will add up/accelerate this, when then forced into the cylinders/callipers (like when replacing pads) the deposits/debris can also score the cylinder walls...

Long-term operation with worn down pads and/or thin, worn down rotors in bad weathers combined with lack off/infrequent cleaning are contributing factors; not only that the brake cylinder walls remain exposed to the elements, prone to corrosion and collecting deposits, reduced guidance due extended cylinders will also cause increased load/wear on rings and bores/walls...
Generally is age an issue, IMO are about 10 years/100Tkm/60Kmiles a good uptime to plan a general overhaul of the brake system; or when one feels significant increased resistance while pushing the pistons in while replacing the brake pads... normally you just grab the rotor edge before & behind the calliper with your fingers, for pressing the calliper towards it with your thumbs, should retract relatively easy (unless their about to seize or the reservoir is overfilled); any significant force required there is an indication for a rebuild being due...
If this rebuild only requires cleaning and new rings, new pistons too or, worst case: also new callipers, depends on age, condition due contributing factors and how long a potential "issue" had been neglected by the servicing workshop, previous or current owner...
Before pushing the pistons into the callipers they should/must always be cleaned (gentle blow with compressed air) and visually inspected; some even use pipe cleaners to wipe the piston walls clean... pushing dirty, obviously crusted pistons back into a calliper is "deliberate destruction of customer property", at least in my opinion/standards...
As already mentioned is brake-cleaner a no go, it'll seep into the gap, cause the outer ring to swell, yet even make it through to the brake fluid, causing more trouble...
 
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thecivvie
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Aug 13, 2013
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Connemara, Ireland
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2000 ST 1100
Thanks for that info. Not being mechanical it is a hard road for me but a friend is going to help me

Ordering stainless steel pistons for front and rebuild kit as well.
 
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