I am having problems with my hayes brakes with pushing the pistons back into the calipers to allow new pads to be interted…. I can push them in some of the way, but not enough to get some new pads and more importantly the rotors between them. I can push one side fully in, then when I try the other side it pushes the other back out again

Is it just that there is too much fliud in the system and I need to let some out?

It is ok to take the bung out of the reservoir and push them in without too much risk of getting air in the system?

Cheers

stick the old pads back in, use a big screwdriver and push the backing plates all the way out until they bottom out on the caliper, then whop them out and stick your new ones in, then stick something in between them. i find the pistons tend to creep out a bit on mine so i always try and change them the day before i want the bike again.

Before letting fluid out try this:

1. Wedge the pads as far apart as they’ll go – old business cards work quite well.
2. Heave on the lever really, really hard a few times.

With a bit of luck this’ll “reset” the position of the pistons and solve your problem.

Hayes 9 brakes are probably the most temporamental brakes around. You’ll probably find that the pistons have siezed whilst the pads were runnng low. Being a phrenolenoliciicicic (or whatever the hell compound it is) they’ll have started to dissintegrate as well. So new pads and pistons all round and they’ll be as good as new.
I know someone who can do a top job of it too.

Have to say all the posts above are wrong (not bad advise, but wrong when it comes to this particular issue), i like most HFX owners have suffered this, what you need to do is:

Put the lever into a vertical position, remove the reservoir plug (this should now be pointing directly up – insert the bleed adapter if you have it, but it’s not necessary), push back the pistons (prefereably using old pads), wipe off the excess fluid that come out of the reservoir bleed hole. Pop the reservoir plug back in, reposition the lever and away you go.

….wipe off the excess fluid that come out of the reservoir bleed hole….

Whenever I took that approach I ended up with spongy brakes that needed bleeding…

9’s are always like this and, as jim says, there’s no point removing fluid – you’ll just end up short of it down the line. Force the pistons apart (screwdriver + old pads does work well), put the new pads in, put up with draggy brakes for the first couple of rides. They soon bed in and stop dragging.