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I've got an old steel-frame road bike which has started making a very unpleasant and worrying buzzing sound when riding over rough/uneven terrain (e.g. roads with lots of fissures/cracks, cobblestones etc.). I've tried

  • (lightly) whacking the metal fenders with my hand
  • (lightly) dropping the bike on each wheel individually as well as together
  • shaking the bike vigorously
  • and hitting/spinning the quill pedals

but I can't seem to reproduce the sound when not riding. What might it be? What steps can I take to diagnose this?

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  • Is there any part of the bike that is particularly weird/worn ? A suspect part?
    – Criggie ♦
    Feb 2, 2017 at 11:17
  • It would help to know where the sound seems to be coming from. There are many odd sounds that can come from the seat. Handlebars sometimes creak in strange ways. Cables can rattle against the frame.
    – Daniel R Hicks
    Feb 2, 2017 at 22:24
  • Am still trying to figure that out: It seems to be coming from more or less directly "underneath" me, i.e. between the handlebars and the chainring, but I can't be sure. It sounds a lot like the rattling I got from another bike which had a cheap luggage rack when it got loose, but all the fenders/etc. seem to be in good order on this bike.
    – errantlinguist
    Feb 2, 2017 at 22:30
  • Can you tape record the sound? An iphone fits in a jersey pocket.
    – RoboKaren
    Feb 2, 2017 at 23:18
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    A "buzzing" sound would most likely be to the fender rubbing against the tread of a modestly lugged tire. It could be that the fender is normally OK, but once it bounces into the "wrong" position the motion of the wheel keeps it from springing back, so you get a constant rubbing that goes away when you stop.
    – Daniel R Hicks
    Feb 3, 2017 at 4:33

2 Answers 2

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Stop riding it immediately!

Remove both wheels and feel the rims for cracks. Tap lightly all the spokes looking for broken ones. Check the wheel for trueness. Grab pairs of spokes and give them a squeeze. You're looking for damage.

If both wheels seem OK then wash the bike and look for cracks under a strong light. Look all round both the chainstays and the seat stays. Since the wheels are off, you can look at the inside of the stays. Then examine the inside of the fork too. Finally look over the main tubes.

If you find cracks, take photos and post them here.

If you find no cracks, reassemble and see if the noise has changed. If you have access to rollers, or a quiet road, try and reproduce the noise. Try variations like this:

  • Coast while standing on the pedals - does the noise increase/decrease?

  • Pedal while standing - does the noise increase/decrease?

  • Pedal backwards - does the noise increase/decrease?

  • Put more weight on the back wheel (ie, put your backside backward, and your belly on the saddle - does the noise increase/decrease?

  • Put your weight well forward (that is, crotch to stem, like a steep climb) does the noise increase/decrease?

  • Lean the bike hard while riding - put the saddle or top tube against your inside knee. Is there any difference leaning to the left vs the right?

Quiet street required because you're not completely focussed on the road around you. Use your best judgement.

If you have a riding partner consider asking them to listen and examine your bike while riding slowly together.

A process of careful elimination might help isolate what area of the bike is the cause.

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I was very concerned about weird buzzing noises coming from my new bike the first few times I rode it, until I realized that the noises were caused by bits of debris (pebbles and such) getting caught between the tire and the fender and bouncing around until they worked their way all the way through the fender. This was my first time riding a bike with metal fenders.

But if you didn't just install metal fenders, and the noises recently started, it's probably not that.

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    Feb 2, 2017 at 22:29

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