Sporadic brake rubbing

bailsofhay

My XT M765 brakes are confuddling me. Most of the time they are silent but every now and then I brake and when I release the brake and they start to rub on the rotor and continue to rub till I tap the brake a few times at which point they go back to their normal silent running. Before everyone says they need aligned, they are aligned just fine and the pads make no contact with the rotor until after I have applied brake force while riding.

Any clue what could be causing this?
Cheers

jimothy78

Sticky seals? Have you tried cleaning the piston edges?

Remove pads, pull lever lightly to advance the pistons (carefully so as not to go too far) - if they don't retract when the lever is released, then wipe around the piston sides with a cotton bud dipped in IPA. A tiny smear of mineral oil may help to lubricate the seals, too, but keep it minimal. Repeat until the pistons advance equally on both sides and retract back smoothly and equally too.

bailsofhay

No not tried that yet, I have some IPA so I will give it a try. As a lube would chainsaw mineral oil work or possibly hair clipper oil, It doesn't have to be hydraulic mineral oil does it?

bailsofhay

Thanks for that Jimothy, That brake was really annoying me and an easy 5 min job sorted it. Only cleaned it but man did it need a good clean.

jimothy78

bailsofhay wrote:

As a lube would chainsaw mineral oil work or possibly hair clipper oil, It doesn't have to be hydraulic mineral oil does it?

I wouldn't like to say - probably not, but personally I wouldn't experiment
At the end of the day, you're going to want to get some proper brake mineral oil for bleeding purposes eventually anyway, so you may as well buy some sooner rather than later.

Glad to hear that cleaning has helped