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I have this problem where my pedals seem to be able to be able to rotate on an axis perpendicular to the straight travel of the bike. To take off the cranks, I need to get past a dustcap. Unfortunately, the dust-cap looks like this:

side view of crankset

That hole in the middle is supposed to be slot for a screwdriver, and I can't get it off. Whenever I put enough force piece to move it (it's been cross-threaded) the metal deforms - it even feels soft.

Could someone please tell me how to get this thing off?

  • Assuming it's a plastic cap (a few are metal but most are silver-plated plastic), just pry/chisel it out. Do note that around it's circumference are threads in the crank arm (used to hold the cap in place) that you don't want to foul up, so be a little careful. The cap is not absolutely necessary, but you should be able to buy a replacement cheaply (or maybe free) at any bike shop. – Daniel R Hicks Dec 31 '15 at 0:18
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At the stage you're at I normally vandalise them out. Get a big flat head screwdriver and use it more like a chisel - wedge the flat under the parts I can see and break them off, trying to break the part that has the thread on it at the same time. Plastic caps usually shatter while I'm doing that and all the bits fall out.

If not I remove the bottom bracket bolt or nut now it's exposed so I have better access, then I get a knife and shave away the plastic until that remaining threaded ring falls apart. With aluminium that will be harder but is usually still doable.

One alternative that I usually try early on is to cut a groove across the ring (parallel to the BB axis) and try using the screwdriver to turn the ring using that.

So far that hasn't failed for me, so I have no idea what to do next. I'd probably use a dremel or a drill to try cutting that ring.

(I've done this quite a lot, I've been a bike mechanic. But 90% of the "stuck" ones shatter when levered open as described, leaving you picking out loose pieces.)

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That's a plastic dust cap. Best bet is to use a dremel to cut a new slot.

Cut the slot to try to unscrew it as normal. After you try that, if it is really stuck or you make the problem worse, you can dig it out, pick it out, or whatever it takes. But don't use any hard steel tool as you might damage the thread in the crank

Upside is that since it is plastic you'll be able to dig it out.

  • ...I thought it had threads on it.. so I'm trying to dig out the threads as well? – user1833028 Dec 30 '15 at 2:11
  • Sorry, I sort of blurred a step. Cut the slot to try to unscrew it as normal. After you try that, if it is really stuck or you make the problem worse, you can dig it out, pick it out, or whatever it takes. But don't use any hard steel tool as you might damage the thread in the crank. – jqning Dec 30 '15 at 2:13
  • @jqning I edited your answr using the "edit" link to add your comment in. You can do that too, rather than making the comments a key part of your answer – Móż Dec 30 '15 at 2:37

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