I have a stock Surly Straggler which comes with Avid BB-7 Road mechanical disc brakes. When I shift my weight to the left on the bike (left crank down, all weight on left foot), the rear brake makes a noise s...s...s...s. When I shift my weight to the right, the noise disappears. So, when it makes a s...s...s...s does that mean that the rotor isn't true? When I shift my weight, does that somehow tilt the wheel a bit?
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Does the wheel have any side to side play if you try to rock it between the chainstays? Or any cracks in the frame, especially the welds connecting the dropouts to the stays?– Jamie AAug 15, 2017 at 14:27
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2If the caliper is adjusted so that a pad is very close to the rotor, putting all weight on one pedal may flex the frame enough to cause that pad to contact the rotor.– Argenti ApparatusAug 15, 2017 at 15:06
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Are you positive the noise is from the rear brake?– Criggie ♦Aug 16, 2017 at 3:44
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I will ride some more and come back. I'm just getting to know this bike.– zedooAug 19, 2017 at 7:36
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1 Answer
Setting up fixed pad BB-7s take some perfection for zero noise. For good brake feel you want the fixed pad to be very close to the rotor. This can result in noise. Is your lever feel good? If it is I would say you are fine.
If your fixed pad (inboard) is not close to the rotor you should look into the following. Either your bearing pre-load is loose on your rear hub or your Quick release is loose in the frame.
edit: spoke tension would have no affect on brake rotor drag
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The noise is, presumably, the pad rubbing against the rotor, i.e., the brakes dragging. I'm not sure I'd really describe dragging brakes as "fine". Sure, it doesn't sound disastrous but it's putting unnecessary wear on the components and it's slowing you down by making you overcome more resistance.. Aug 16, 2017 at 9:32
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For a cable actuated brake with a fixed pad and with no floating caliper or floating rotor yes this is "fine".– emoneyAug 22, 2017 at 13:46