Front brakes binding

[V4beermonster]

A common problem with many bikes with binding brakes is the relief/return hole in the master cylinder gets blocked (it under the plastic bit the resivior hose attached too) on the m/c.

[Ben_OB1]

If we're talking about "dragging" rather than binding, I have encountered the same thing on my RVF.
I discovered an old technique, and although not convinced it would work I gave it a go.

1. Remove the caliper from the brake rotor.
2. Push both pads all the way back against the stops so that pistons are fully retracted.
3. Refit caliper and fit mounting bolts secure but only finger tight. Back off the screws ever so slightly so there is a very small amount of float.
4. Whilst squeezing the brake lever secure and torque the caliper bolts.

I expect that this technique is simply preloading the rubber seals.

Just be aware, this might give you a bit of free-play in your brakes as the pistons extend to reach the rotor. A bit of fiddling and you should be able to optimise the dragging versus freeplay relationship.

Then again, a bit of copperslip on the piston seals might make all of this irrelevant

Ben.

[Neosophist]

If we're talking about "dragging" rather than binding, I have encountered the same thing on my RVF.
I discovered an old technique, and although not convinced it would work I gave it a go.

1. Remove the caliper from the brake rotor.
2. Push both pads all the way back against the stops so that pistons are fully retracted.
3. Refit caliper and fit mounting bolts secure but only finger tight. Back off the screws ever so slightly so there is a very small amount of float.
4. Whilst squeezing the brake lever secure and torque the caliper bolts.

I expect that this technique is simply preloading the rubber seals.

Just be aware, this might give you a bit of free-play in your brakes as the pistons extend to reach the rotor. A bit of fiddling and you should be able to optimise the dragging versus freeplay relationship.

Then again, a bit of copperslip on the piston seals might make all of this irrelevant

Ben.

NEVER put cooperslip on the piston seals.

Copperslip is an anti-sieze compound and pretty abrasive at that. Sure it will stop them sizing but it will destroy your pistons over time. Same reason why your not supposed to use it on sliding pins etc.

Sure many people do and many times it doesnt cause major issues but ive scraped rock hard copper slip thats dried out from many sliding calipers before. Also replaced many ruined seals becuase of it too.

http://www.landcruiserclub.net/forums/s ... ke-pistons

Some photos here of some numpty using comper grease on seals.

You can see how the solvents in it attacked his seals and made thems well up over night.

Brake seals are quite resliant stuff but just becuase it might not cause and harm doesnt mean its good to follow bad practice, besides I wouldnt want to make the seals any weaker.

[Ben_OB1]

Hey Neo,

Some great advice there regarding copperslip. I haven't used it myself, hence the need to use the "loose bolts trick", but I am very interested to read your comments. I will save the copperslip for lubing fasteners!

Ben.

[bkk2009]

I had the same problem on my NC30, but they were really binding after about 20 minutes of riding. They would stop the bike, and couldn't get going again and an awful burning smell. Only way to make it home was to crack open the bleed screws at both front calipers to release some fluid pressure and ride home. Replaced the brake lines, rebuild the calipers like you did (replaced all seals, cleaned out the calipers and light buffing of the pistons), but still would bind. It ended up being the master cylinder. The piston was binding somehow and not allowing the brake fluid to release the pads. So I replaced the brake master at the handle bars and all was right again.