possible causes for pads not returning

i have a pair of hayes mags and the pistons are not returning properly. after a short time the bike will become un-ridable.

What are the likely causes for this? and maybe some solutions?

cheers

Clean them?

i have raised the pistons out of the caliper and cleaned them but the didn’t seem to work, they looked clean. Is striping the caliper down my only option?

Both pistons on one of my bikes had ceased think it was the salt on the roads being the main issue (they are transported on a boot rack), took both pads out and sprayed some cleaner, this freed the pistons enough for them to pop out a little, bit more cleaner and all is good.

By cleaner I mean the stuff that is disc safe and evaporates.

i have done that and the pistons seem to move out ok but they are not moving back as easily. It only takes 10 mines riding and they get to the point that i can’t spin the wheels when off the bike.

Before stripping them, invert the lever, remove the bleed screw from what is now the top,and try pushing the pads back then. It may be a little too much fluid in the system. Failing that, routine stripping, cleaning, and reassembling with a silicone grease is always a good idea anyway.

I did what you sugested and no fluid came out. I have just striped the caliper and the square seals look like this

is this normal? Have i found my problem with this brake? if it is normal which way should the go back in to the caliper?

Thanks for the help so far

Yep, normal for an old seal. If you check the groove in the caliper body, you’ll see it’s cut at an angle, this allows the seal to flex and return with the piston movement, and causes the piston to retreat back into the caliper slightly when you release the lever.
Clean everything thoroughly(including the seal groove)and check for corrosion in and around the groove as this can tighten the seal and cause sticking. Smear a little silicone grease on the seal and piston before fitting, and match the angle of the seal to the groove angle.

thanks coatesy. hopefully that will do it