Sticking brake piston

[Premature Accelerato]

Sorry, a typo. Meant to be scribber. Its probably a bit heavier than a dentists tool but was used gentlly and didn't scratch the hell out of the casting. Their was a little bit of crap there, not a huge amount. Guess I will have to pull the other caliper apart to get a good comparison.

[Grumph]

Cleaned it with the curved end of my trusty old scrubber. I have just pulled it apart again and put the piston in the pot without any seals. It slides in and our easily. I then put the oil seal in by itself and the piston works the same as the others. I then put the dust seal in and the bloody things tightens up to buggery. So I would guess that perhaps the seal is slightly too big or the seal is a little over size. All the extra cleaning at least gets me a 1 1\2 turn of the wheel when I give it a spin. Enough ya reckon?

Surely you mean the dust seal is Undersize. Are you putting any rubbergrease on the OD of the piston or the ID of the seals ?
Turning the dust seal inside out can often reveal accumulated crud.
Bit like inspecting the ID of Methamfeatherston I suspect....

[Premature Accelerato]

By over size I mean it is too tight but I guess you could call it undersized. I have put a small smear of grease I got from Boyles a couple of years ago, to lubricate things. I have used the same grease many times on brake seals and it has never given me any problems. It is red in colour but I cant remember its brand/trade name. I'll get there in the end.

[jellywrestler]

Surely you mean the dust seal is Undersize. Are you putting any rubbergrease on the OD of the piston or the ID of the seals ?
Turning the dust seal inside out can often reveal accumulated crud.
Bit like inspecting the ID of Methamfeatherston I suspect....

i snuck up the hill a wee while ago and altered their sign.....
take a good look at the little square boxes too.

[jellywrestler]

so did you just replace one seal?
did you clean the grooves out thouroughly, ie with a solid scraper to pick the shit out of it,
if you move the seal to another hole them if the issue follows it there it's the seal,

[Voltaire]

Its unlikely but if the compensation port ( very small hole)in the master cylinder is partially covered by the piston seal pressure builds up and pads drag. can be caused by sticking brake lever/actuation mechanism.

[Premature Accelerato]

I have now cleaned the absolute shit out of these calipers. I measured the dust seals and the offending seal was actually 0.2mm thicker than the nearest sized seal. I have put that seal in a different pot with the smallest dia piston (albiet by only 0.02mm). Although the amounts are not much, surprisingly the wheel now spins quite freely.

[jellywrestler]

I have now cleaned the absolute shit out of these calipers. I measured the dust seals and the offending seal was actually 0.2mm thicker than the nearest sized seal. I have put that seal in a different pot with the smallest dia piston (albiet by only 0.02mm). Although the amounts are not much, surprisingly the wheel now spins quite freely.

yah that's 5 thou, for the seal, usually it's lumps in the grooves that can't be easily seen that cause the issue., well done

[Scubbo]

time to upgrade to nissin calipers --- glad to hear its sorta-sorted ...