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As above. Doing a drive train overhaul, just finished and pulled front brake on and it stayed stuck on. I could get the lever to pop back out by manipulating the pistons, but it wouldn't return as normal.
I have managed to free it by creating a sealed environment and letting GT85 penetrate it overnight. It now works pretty well.
My worry is that this might not have done good things to deals etc. Does anyone out there know if there are any vulnerable seals I might have compromised? Brake is a Shimano SLX lever, probably 3-4 years old.
Any advice gratefully accepted.
It should be fine, basically the rubber seals can put up with it for a while. I would have thought that length of time is not long enough for the evaporating element in GT85 to damage the seal. A few days / weeks maybe, but not overnight.
Id put it back to gether and see if it still works.
This problem is dependent upon the type of brake fluid that the seals are designed to resist.
Shimano SLX uses Mineral oil and the lubricant element of GT85 is also a Mineral oil...
Therefore it will be fine.
It would have been a problem if the two were different i.e. a brake that uses glycol ester based fluid (DOT 4 etc...) and GT85 would cause an issue with Seal swell and potential failure. No matter how short the exposure!
I've had this on my shimano xt brakes before. I stripped and cleaned it and put it all back together and it worked fine for a few rides but then did it again.
On mine it was a slight build up of dirt that stopped it moving. I've seen some videos where they sand this down.
In the end I bought new levers and sold mine on ebay as spares. The levers and tops caps etc are worth a little bit to people trying to keep their brakes going. So some of it was recycled.
Unfortunately shimano is designed to be replaced unlike hope brakes.
Thanks for the replies folks. I will clean them up stick the pads back in and test them a bit on a spare rotor to make sure they are ok.
New GT85 = fine
Used GT85 = wrecked brakes
Have you bled them? One of mine was sticky, and the fluid was filthy. New fluid and it seems fine.
Shouldn’t be fluid as it was a new caliper on an old lever, only a couple of months old and filled from fresh.
Tried it again when I got home tonight and it is sticking again. CRC have good offers on at the moment so bought a new one and will chop the caliper off and keep as a spare.
Thanks for the advice folks.
JAG
Subscriber
This problem is dependent upon the type of brake fluid that the seals are designed to resist.
Shimano SLX uses Mineral oil and the lubricant element of GT85 is also a Mineral oil…
The solvents could also be a problem. But less likely since they don't linger
Get some silicone spray, it's good for fork and shock seals too and good for keeping stanchions smooth n slippy.