Second hand bike, my first time encountering Hayes Sole brake calipers. My brakes front and back have gone a bit weak so I wanted to tighten them up a bit. Each side of caliper has an allen key section that pushes in each brake pad. When you pull the brakes(hydraulic) one pad moves in and the other is static. https://www.parktool.com/blog/repair-help/hayes-hydraulic-brake-service

Front brakes are okay, I could screw in the static side a bit while the moving side is already all the way in(it does screw out ok), brake pads look like they have a bit more life left. Braking feels ok now but maybe not super strong. :-7

Back brakes both sides are stuck, I can neither screw them in nor out. I have cleaned a bit will leave oil/WD40 (WARNING! you should lubricate using DOT brake fluid, especially do not get oil/WD40 anywhere near or on piston seals or brake pads or brake disc) soak in and start using more force tomorrow but I was wondering is this a problem someone else has encountered, does anyone have any experience and advice with regards to these brakes?


  • "will leave oil soak in" -- Are you putting oil on the piston seals??? This will cause the seals to swell and jam the pistons! Some bike disk brakes use oil, but the Hayes (see your link) uses DOT brake fluid -- basically an alcohol/glycerin mix. This type of fluid is used in large part because it doesn't attack rubber parts like regular mineral oil does. Oct 21, 2018 at 1:03
  • Ah, yes I put on oil and also WD40, oh dear, one side isn't a piston seal so I guess oil would be ok there. Cause the seals to swell ? :( So best to try lubricate with dot brake fluid. Would WD40 also be bad?
    – gaoithe
    Oct 21, 2018 at 1:23
  • Yes, WD40 would be bad. (And note that it is very important to keep any sort of lubricant off the discs and pads.) Oct 21, 2018 at 2:12
  • Yes, it's dodgy spraying WD40 near brake discs & pads, I know, I was careful! Anyway, update: I had wiped off oil/WD40 but no DOT brake fluid to hand so I left it. The next morning I tried again and both sides shifted, so I think the WD40 did help! I guess it would be ok on the non-piston side as long as you are careful. But it could lead to trouble on the piston side.
    – gaoithe
    Oct 22, 2018 at 12:53


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