What kind of crank extractor do I need I'm trying to swap the cranks on our Thorn tandem and would like to know what kind of crank extractor (if any) I need for the job.

Is there a way to tell from this photo, before I've taken it all apart?

EDIT: Photo updated after cap removed (sorry it's a bit blurry). Centre has a thread, is that what I'd screw into and pull?



For example, Thorn list several crank extractors.
You will need a specialty tool referred to as a crank remover or crank extractor. A Park Tool CCP22 or something similar. I would suggest considering the Park Tool CWP7 or equivalent as it offers increased flexibility. While the CCP22 is suggested for square shaft interface the CWP7 will do square, splined and octolink. While you only need the square type now the universal design of the CWP7 may come in handy later.