Noise from front disk brake under pressure

[kwwmackenzie]

Morning,

When I'm cycling and lean to the right there's a rubbing noise coming from the front disk brake, the pads are rubbing against the disk. When I cycle upright, there's no noise and no contact. The brakes have been calibrated and no contact when I check. Lean to the left and again, no noise. Took my bike to my local store who checked the front hub, replaced the ball bearings etc and said the wheel was fine. Tried the bike and again the noise was there.

Local shop suggested maybe the forks were flexing too much.. i had my forks replaced under warranty (bike is only 7 months old) - again the noise is there.

I'm running out of idea's as to what this is... any thoughts

thanks

[RobAR]

You don't say which disc calipers and what size rotors but, it's not an uncommon occurrence. The larger the rotor, the more probable of it happening and, yes, it's due primarily to fork flex. It's not necessarily a fault of any component - just the nature of the beast.

You might ensure that the skewer is plenty tight and then make sure that the rotor is truly centered between the pads. It should not flex to either side when you apply the brakes unless you have a caliper with a single piston and a fixed pad. Even these can often be better-centered by a good mechanic.

As it only happens in a right lean, that sounds to me that you have a fixed pad on the left and the torsion on the fork is pushing the rotor into that pad.

Some 29'er wheels, due to their size, are just prone to this.

[xerxes]

(06-11-2012, 05:22 PM)RobAR Wrote:  It's not necessarily a fault of any component - just the nature of the beast.

I'd be inclined to agree, with disk brakes, the pad is very close to the disc with just a millimeter or two gap and they do have a tenancy to rub. I find it difficult to adjust mine so as not to rub at all.

With some of the dearer hydraulic systems you can adjust the pad spacing to minimize the problem, but mine have no such facility.

[Tim M]

The tolerances are pretty close. I eventually decided it was roadway imperfections (little bumps) and when it gets really persistent and irritating, loosen then tighten the wheel. That helps for a while. It's intermittent and decided to not worry it too much.

[kwwmackenzie]

Thanks for all the replies. The brakes are shimano alfines with 160mm rotors. The pistons are auto adjusting, been re-calibrated and when spinning the wheel when the bike is on a stand there is no contact at all.
In terms of the bike performing.. i guess its not an issue (I just dont like noises on my bike that I dont expect to hear ;-)), dont quite get whats caused it though as it only started happening after about 6 months of having it.

[kwwmackenzie]

With further tinkering.. I removed the brake pads and put the pistons as far back as they go and there is still a noise coming from the front.. I'm starting to think now its the hub (or the wheel in general)