So I'm resuming work on restoring a bsa bike for my sister.

The first thing I need to do is strip it as it's in need a of new paint job.

I'm having trouble removing the crank arms.

They appear to be bolted on using a round headed bolt then a nut on the other side.

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Is there something am doing wrong because the bolt doesn't appear to come out. Even when I whacked it multiple times with my hammer it still didn't budge.

  • 3
    The old cotter-style cranks were always a PITA. "Tapping" the bolt was the usual first resort, but except on really new bikes it always ended up damaging the bolt (even if one screwed a nut part way on to protect the threads). The "right" way to get the cotter bolt out was to use a special-purpose vice-like press, but these were rare 30 years ago and probably impossible to find anymore. And, before you go any further, make sure you have a replacement cotter bolt, as you will certainly need a new one to reassemble. Jan 10, 2018 at 23:21
  • 4
    Well, actually, here's one "cotter pin press" which is apparently still available: bikesmithdesign.com/CotterPress Jan 10, 2018 at 23:22
  • 1
    When you do get it out, consider replacing the BB with a modern cartridge bearing and modern 3piece cranks. The only reason for staying with old cottered cranks is if you value "authenticity"
    – Criggie
    Jan 10, 2018 at 23:48
  • 1
    I won't be able to reuse the front chain ring if I upgrade the BB would I?
    – Ageis
    Jan 11, 2018 at 0:00

2 Answers 2


Use a length of conduit or other metal pipe or some other kind of brace to transmit load from the crank to the ground, so that the hammer impacts are not going right into the bearings. Then hammer it with everything you've got. Try to go for fewer strikes and more power. It's a press fit you're overcoming; it's supposed to be stuck.

Always plan on having to replace the cotters. They don't necessarily get too mangled or bent to re-use but they often do. Replacements are still pretty available, although there are multiple diameters (I think 4). You re-establish the press fit with a hammer or press, never via the nut - it can shear the cotter if you try. Sometimes you have to file new cotters to make the angle right (make the cranks 180 degrees apart) if you only replace one of them. The other very important thing is to re-tighten the nut on a freshly installed cotter after a break in period at first, say 50 miles.

Despite being a pain, they do work and all you really need to work on them is a hammer and piece of pipe.

  • 1
    One important point when re-installing the cotters is to understand that they can be inserted two ways, but only one of those ways is correct. If you get them in wrong the two cranks are not lined up with each other. Jan 11, 2018 at 1:22
  • Cotter pins are 'consumables' and should always be replaced although they might occasionally hard to find.A shop selling vintage parts maybe, but then those would possibly have the extractor mentionned by @Daniel R Hicks
    – Carel
    Jan 11, 2018 at 19:49

Check out Sheldon Brown's page on this topic

  • 1
    Please avoid link-only answers. The remote web site could vanish or reorganise, leaving dead links that are no use. Instead, duplicate the main points in your own words into the answer. Having a link as "supporting information" is fine, but the answer should stand by itself.
    – Criggie
    Jan 15, 2018 at 0:41

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