Rear brake still sticking after servicing.
 

So I 've just overhauled my rear caliper for the second time in a year. Meticulously cleaned out again, although there didn't seem to be any corrosion in there anyway this time. New seals again just because I had them ready, but old ones were ok. Pins, sliders etc all good. Plenty of red rubber grease. Bled well. Even all the small pressure plates polished up and spotless. But the piston still doesn't like retracting back into the caliper when the brake is released. I can push it back in by hand no problem though, so it's not jamming. More like it's not getting sucked back in... possibly the fluid not returning?


The brake is definitely dragging as disc and caliper are very warm after riding with only very slight occaisional rear brake use.


I'm guessing next I need to be looking at the master cyclinder? All seemed to be moving ok during the bleed with lots of lever travel which firmed up obviously once bled.


Has anyone got any other suggestions before I pull it apart again and take the master cylinder off and apart to check?

Re: Rear brake still sticking after servicing.
 

I have heard of an effect where the internal rubber of a brake line collapses and acts like a non return valve so the brake still operates but the fluid cant return to the M/C. I dont know if this is an urban myth but is something worth checking probably after everything else.....

Re: Rear brake still sticking after servicing.
 

I've not heard of that but that's the sort of thing I'm thinking. I did fit a new Hel line from MC to caliper when I last serviced it less than a year ago. Possibly something going on from MC to reservoir though? Or even though it doesn't feel like there's any problems with the piston in the MC sticking when applying the brake, maybe it's sticking when brake is released. I'm going to pull it apart today and see if anything obvious is causing it.

Re: Rear brake still sticking after servicing.
 

more than likely you have the pad retaining clip round the wrong way. the long "tabs" go to the pistons.

https://i.postimg.cc/5NBFDJXG/clip.png

Re: Rear brake still sticking after servicing.
 

I can only tell you what I had to do on one of my old Hondas front brake callipers.One side front had a sticky piston.It looked ok but under a magnifying glass there was some slight corrosion that with my normal glasses I didn't see.I polished the piston with some Autosol Metal polish and that cured it and cleaned off with carb/brake cleaner.

I use ACF50 on the seals and piston when they are in and have had no problems since.I did my SVs the same way when I got the bike last year both front and back.

Although the Rear pins cleaned up OK they were a little pitted and one of the spring retainers was shoddy so replaced them with this kit,

https://www.ebay.co.uk/itm/AFTERMARK...x5tb:rk:3:pf:0



£4.95



The springs in this kit were slightly different to the ones that came off but still work and are actually easier to fit/work with.



HTH :)

Re: Rear brake still sticking after servicing.
 

The master cylinder will only open the port to connect fluid to reservoir when the piston is in its fully retracted position, this is to allow any air to escape and fully remove any pressure from the circuit. Is the piston being stopped before end of stroke by brake lever before it gets back to fully retracted ?

Re: Rear brake still sticking after servicing.
 

That got my hopes up that it was something simple... ran out and took caliper off. But, sadly it is the right way around.

Re: Rear brake still sticking after servicing.
 

Cheers, but it's a K8 pointy so different bits. All sliders etc are very good and clean. The piston is a new stainless one fitted less than a year ago. Bike has done less than 600 miles in that time as it was sorn for 6 months.

Re: Rear brake still sticking after servicing.
 

I've got the MC off now but will check this when I reassemble if it's still happening. Cheers for the info. Helps narrow it down a bit.

Re: Rear brake still sticking after servicing.
 

Shame :(

You might find something from another forum/search,

https://tinyurl.com/y8er4rml