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My partner has a Kona Sutra with Avid BB-7 disc brakes. The front brake rubs intermittently on the rotor. I just went to see if I could figure out what the problem was and right now the disc runs true and quiet. The disc is a Shimano CenterLock on an Alfine dynamo hub.

Usually when we notice the rubbing it is part way through a ride. Our usual route takes us down a relatively steep hill early in the ride. I'm wondering if the rotor could be warping from the heat of braking down the hill – though I'm not sure why it would stay warped for the next 20-30 minutes (for the rest of the ride).

Any suggestions for things to check or ways to isolate the problem?

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After working on this for way to long, I think the problem is a combination of oversized dropouts and not enough tension on the quick-release. I discovered that if we stopped and loosened the quick-release while making sure that both axle ends were seated in the dropout that noise would stop.

I think what was happening is that the force applied on the disc would cause the wheel to shift a bit in the dropout and start rubbing. Each time I did this I tightened the quick-release a bit and after a few tries it seems to be resolved. I'm surprised by how much I had to tighten the quick-release. It is way tighter on this bike than on my bike which has rim brakes.

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  • Excellent spotting - noone else suggested this. The forces of a disk brake are huge, and with the caliper/calliper on the rear of the fork tine it generates downwards force on the axle. Really we should put the calipers on the front of the tines - dunno why this isn't done. This is also the reason for the rise in popularity of through-axles ( or "thru axle" for the alphabetically disadvantaged) No way the wheel can come out then.
    – Criggie ♦
    Mar 6, 2016 at 2:42
  • Wow, a front wheel moving in its dropouts would definitely give me the creeps: Just imagine what would happen if it worked its way out of the dropouts! I definitely prefer my quick releases to be as tight as possible...
    – cmaster - reinstate monica
    Aug 29, 2018 at 9:01
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Check the front wheel bearings. The preload could be off.. Or they could have lateral play. If they have lateral play then the whole hub could shift causing the rotor to rub.

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I've had this happen as well (BB7 as well). The only working hypothesis I have is that the rotor has small imperfections, for example small deflection, which is made worse by heating during braking resulting in the audible rubbing. Once the rotor is warmed up it may take a while to cool down sufficiently if you use your brakes periodically after the initial warm-up.

I also wonder if heat could change the tolerances by expanding the pad volume slightly. I'd expect the pad to take longer to cool down given the more protected placement. (I don't know enough about all the materials involved to know if this is feasible.)

As a quick test, make note of the rotor deflection and tolerance before you ride. Do your usual route until you hear rubbing, then recheck the tolerance and deflection. This could be difficult to measure without specialized tools.

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  • The idea about the pads is interesting, I hadn't thought of that. We rode tonight and the rubbing started after a long (but less steep) downhill, we stopped to check and the rotor was warm (distinctly warmer than ambient, but not hot) and the rubbing had stopped. I'm thinking more and more that it is a heat thing. There is a lot of material left in the rotor, I don't think they are even close to worn out, but it might be a defect of some sort.
    – dlu
    Oct 17, 2015 at 2:55
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    Opening the adjustment screw on the brake by one click does wonders, without compromising the stopping power. But first, re-adjust the brakes according to the manual, by loosening the bolts, braking firmly, keeping the lever locked and re-tightening the bolts. (You need at least 3 hands for this!)
    – Carel
    Oct 17, 2015 at 10:16
  • Are both rotors the same size? Can you swap front and back rotors over to see if the problem stays with the metal disk or with the caliper/calliper and brake pads?
    – Criggie ♦
    Oct 17, 2015 at 11:05
  • @dlu another test I have done is to build up speed then do a hard emergency brake to get heat into the brakes. They will often make the rubbing sound for a bit the disappears after a bit (when the heat dissipates). As Carel suggests backing the pads off by a click will give a bigger rotor/pad gap which can alleviate the noise. Personally, intermittent rubbing doesn't bug me much.
    – Rider_X
    Oct 17, 2015 at 16:27
  • Wheel bearings in good shape? A little too much slop there can mess you up pretty good.
    – zipzit
    Oct 18, 2015 at 16:28
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This happens to me on my back wheel. No matter what I do, after a big hill or downhill my back wheel starts to rub. It is getting really annoying and I am almost convinced either to get a rim brake or a Thru-Axle bike.

What I think there are 2 reasons for disc rubbing in the back wheel:

  1. When you apply brakes on downhill
  2. When you are putting a lot of power on your pedals

Both occasions, the wheel might get slightly pulled to either side (depending on the force that comes from brake/chain).

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  • If putting a lot of power through the pedals causes brake rubbing, it's more likely to be the frame flexing than anything else.
    – David Richerby
    Aug 29, 2018 at 10:50
  • What I am saying is that both ends of the axle generating a lot of force that is enough to wobble the axel in the dropout, which eventually cause tiny bit of movement which then leads to disc being drawn to one side. At least this is how I understand it. Thru-Axle addresses this very issue.
    – Manoj De Mel
    Aug 30, 2018 at 0:32

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