hydraulic disc brake help

[bkboom123]

I transferred a set of shimano disc brakes from an older bike to my friends bike. These shimano lx brakes can't have more then a hundred miles on them, and the pads look fine to me. The rear brake is perfect, quiet and strong. The front brake however screams like a son of gun, and isn't nearly as powerful as the back. Quite under powered actually.

No idea what's up with the front brake. I just bled it ten mins ago, and the lever throw feeels perfect. But it still screams and is way under powered. Any ideas?

[Ken Robb]

If you have a firm lever after bleeding and the stopping isn't good I think it has to be due to reduced friction between the pads and rotor. Try cleaning both with a solvent like acetone or automotive brake cleaner. If that doesn't help I would guess something has contaminated the pads and you will have to replace them. If you clean the rotor and swap the pads that work well on the rear to the front for a test you could know if new pads are the answer.

[Germany_chris]

My guess...you got a bit of brake fluid on the pad..and if I remember right Shimano says that if that happens you need to replace the pads

[bkboom123]

I highly doubt its the pads being worn, as I said there is minimal use on them.

Could a litte brake fluid being spilled on them really make it soo bad? I sanded the pads and the rotors.

[vqdriver]

I'd think an easy test would be to take the pads from the rear and try em up front.

[Germany_chris]

Yes..
I've tried sanding too, never worked.

I highly doubt its the pads being worn, as I said there is minimal use on them.

Could a litte brake fluid being spilled on them really make it soo bad? I sanded the pads and the rotors.

[d_man16]

Take the lever depress it and in the other hand try to rotate the wheel backwards- if the squeaking goes away then the pads are not seating well and probably need to be replaced as one dose not have even wear this can happen quite quickly. I'm not sure what model you have but switching out the pads should be pretty easy some of the older shimano's had a cotter pin in them which was a little bit of a pain in the bum.

if that does not work then you might need to shim up the caliper depending on the model if it has an (IS) mount which is the one with the two holes parallel to the pads you might need to add those little shims until the pads are centered about the disc.

If you have a post mount and the pads didn't work then loosen the two bolts and depress the caliper and then retighten the bolts sometimes it does not work on the first try.

If all that does not work then look into the rotors.....Shimano has decent rotors and I've never really had a problem with them...

Hope that helps