I am restoring a 1970 Schwinn Suburban and I am at a loss when it comes to removing this bottom bracket. The crank arms do not come off normally (no way to use a crank puller) and they won’t unscrew. I have put some lube on the side opposite the drivetrain and maybe I need to wack it with a mallet but any advice would be greatly appreciated!! drivetrain_side kickstand_side

2 Answers 2


This is what's called a 'one-piece' or 'Ashtabula' crank.

There is a nut you have removed (or that was already missing) on the threading. Then you remove the left cone via the slot in your second image. Sheldon explains better than I do: https://www.sheldonbrown.com/opc.html

  • Thank you Allen! You responded so fast!
    – duhnlic
    Commented Mar 1, 2023 at 17:16

Alan is correct.

Here's a diagram of this type of crank. Sheldon describes it with words but sometimes a picture helps.

enter image description here

The left side in the picture above is missing both the locknut and the lockwasher.
In an ideal situation you'd have a bottom bracket wrench for one piece cranks
enter image description here
If you are careful sometimes the adjusting cone can be removed with a screwdriver pushing on one of the slots.
The locknut and adjusting cone are left hand threaded.
Here's a Park video on this process.

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