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Hi all,

I've got a Dawes Imperial (Reynolds 531 frame) and the crank arm is loose. None of my standard impact drivers fit. Does anyone know what I need to use to tighten it?

Thanks, Tim

  • 2
    1) The type of frame has little if anything to do with the nature of the crank arm. 2) It's not entirely clear whether you are saying the crank ARM is loose on the crank SHAFT, or that the crank SHAFT is loose within the bottom bracket. But most modern crank arms are tightened with Allen (hex) wrenches, and you would never use an impact wrench to tighten one (or anything on a bike, for that matter). Commented Mar 1, 2017 at 18:42
  • Welcome to Bicycles @timpwbaker. We recommend that new members take the tour to make best use of the site. That looks like a 15mm (sometimes a 16mm) socket is needed. If yours don't fit you could get one at the bike shop, ask them to do it, or try your local bike co-op.
    – andy256
    Commented Mar 2, 2017 at 1:12

2 Answers 2


I'd use a 14 mm socket to undo the nut/bolt. Then you need a crank puller tool to lever the crank off the bottom bracket axle.

Daniel's point is correct - are you positive its the crank/arm to axle that is loose? Its more common to have misadjusted bearing cup/cones in the bottom bracket, and the whole pedal-structure wobbles.

  • Yes that's what I tried, sorry, impact socket was what I meant. None of my set fit, the space around the nut is too tight. I've only ever needed hex keys to tighten the crank arms on my other bikes. Feels like the arm is loose, but I won't know if it's the whole bracket until I get the arm off. It's only the tiniest of wobbles on each peddle rotation
    – timpwbaker
    Commented Mar 1, 2017 at 20:49
  • @timpwbaker yes I bought a long 14mm socket just for cranks. It had thinner walls than my existing 14mm socket. "Impact" sockets are built to be hammered by the tool (impact driver) and are really overkill on a bike. That said, I've used mine a couple times only for un-doing tight stuff.
    – Criggie
    Commented Mar 1, 2017 at 23:26
  • Thank you, I've bought a thin walled 14mm socket, if that doesn't work I'll take it to a shop. I can't upvote as I'm new but the help is much appreciated.
    – timpwbaker
    Commented Mar 2, 2017 at 17:39

If you are using a 14mm socket that is 1/2" drive it may be too thick to fit in the opening. Try a 3/8" drive 14mm socket, the wall thickness is thinner allowing better access. If you can't get enough torque with the smaller ratchet handle, get an adapter that allows using 3/8" drive sockets with the larger 1/2" drive handle


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