Sticking Hydraulic brakes

JimmerG
JimmerG Posts: 143
edited January 2009 in MTB workshop & tech
I've got Shimano deore, dual control hydro brakes, they're just over a year old and never been serviced.

They've always seemed a little spongy, and slightly lacking in power, they've also been a bit squealy - but I reckon this could be the pads, so I've got some new ones on order. I've also been cleaning the disk with disk cleaner.

So - I had a stab at bleeding the front brake, and you've guessed it - its worse. No air was seen to leave the system, and now the lever is spongier, it doesn't return with the usual snap, and there's no obvious bite point. The pistons are not equaly pushing towards the disk, AND they're struggling to return back into the caliper. Indeed the pads are now binding onto the disk.

The thing is I simply can't see where the air has got in, and couldn't get any air out. There was just an unbroken stream of oil.

Do all the symptoms above sound like there's air in the system, or do I need to strip and clean the caliper and pistons?

If indeed I try and bleed it again - should add oil to the reservoir and try to bleed air out of the caliper? Or should I be adding oil to the caliper and watching for bubbles in the reservoir.

I suspect I'm making a simple matter very complicated - this is the first time I've attacked hydraulics - and it's a worry that its the only part of my bike that remains misunderstood!

Comments

  • ride_whenever
    ride_whenever Posts: 13,279
    If you're on good terms with your lbs get them to show you how to do it properly. Much easier than trying to muddle through on your own.
  • JimmerG
    JimmerG Posts: 143
    Just thought - I didn't push the pistons all the way back into the caliper when 'trying' to bleed them. Might this have been my mistake?
  • could be, Shimano supply a little bit of plastic for this reason to hold the pistons back when bleeding the brake. Or you can use fresh pads with the rotor in, just need to be careful no oil gets on them, and make sure they are all the way back.
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