I'm used to single rider bikes, but new to tandems. We have a specific creak that I (as captain) can also feel through the pedals. It's on every strong stroke of the captain's pedals, left or right, but if I take my feet off and let my stoker pedal, it doesn't happen. She also can't feel it reliably through the pedals when I cause it. But she is only about 1/3 my weight (also 1/5 my age, and inexperienced).

The bike has an eccentric front BB, and the creaking started a few tens of km after I had to change the front crankset (the previous owner is not to be trusted with screw threads). I've already made sure the cranks and pedals are on tight. I plan to check the chainring bolts, but could the BB cause this? Is there something else tandem-specific I should look at while I'm at it?

  • Is the frame intact? The one time I had a persistent creaking sound when pedalling that I couldn't track down to any problem with the cranks or BB, it turned out that there was a crack growing across the down tube.
    – DavidW
    Dec 22, 2022 at 20:34
  • @DavidW I can't see any sign of damage, and it hasn't had any hard use in the few months I've had it
    – Chris H
    Dec 22, 2022 at 21:05

2 Answers 2


It did turn out to be (almost) tandem-specific: the eccentric bottom bracket was moving slightly even though the bolts securing it seemed tight (when tested with a multi-tool).

This model uses two M8 bolts into the underside of the BB housing on the frame (not a Thorn but a similar design). Other designs use a wedge. The left bolt was holding but the right allowed a fraction of a millimetre of play. I adjusted the chain tension slightly at the same time so the bolts are now clamping onto a different bit of the BB shell. I didn't remove the cranks so haven't inspected the BB itself.


Try attaching something damping to the keel tube and see if that changes things. The keel runs between both bottom brackets and can function as a resonance amplifier because it has vibrations at both ends.

As a test, temporarily wrap on some scrap cloth rags with some tape to stop them sliding back. If that helps, there are more elegant solutions like that stick-on foam used in cars for noise damping - a strip of that down the underside might be all it needs.

  • I'm wary of damping things until I've ruled out a real cause, so I was keeping this in reserve. But I got the chance to look at it in good light, and I'm pretty certain I've caught it
    – Chris H
    Dec 24, 2022 at 20:31

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