Originally Posted by well biked

Are you sure it's not a square taper bb? If it's Deore, Deore LX, Deore XT, or XTR, it should say so on the cranksarms. Those were the mtb groups that were available with Octalink I believe. My wife has an Alivio crankset on her bike that just says "Shimano" on the crankarms, it uses a square taper bb. I don't believe Alivio was offered with Octalink, but I could be mistaken. Or maybe what you have is just an OEM Shimano crankset, not really part of a "group", but with an Octalink bb. I don't know.