Originally Posted by HillRider

That's exactly how it works on Shimano self-extracting cranks. The bolt is loosened with an 8 mm hex key and after the first turn or so it gets tight as it butts up against then outer ring. Keep turning the hex wrench and the entire arm comes off.

A standard square taper extractor won't work as this is a hollow Octalink spindle. You need the appropriate Park tool or Shimano tool with the wide screw press tip or the Shimano "mushroom" TL-FC15 if you remove the outer ring first.