Which cranknut do I need?
 

Hi all,
Im missing a cranknut on my bike. Not sure which crankset i have but i think it's a hollowtech I (not II). I order this cranknut (shimano Y1P417000) but it is too big. Anyone know where i can find a smaller version?

Hollowtech 1 can be square taper or octalink. I'd remove the bolt and look at the interface. If you see a square, you need something like this.

If it's a Shimano crank, there should be a part number on the inside of the crankarm just below the hole for the pedal. That'd make it easy to determine what you have.

If this turns out to be Hollowtech II then the "nut" you seem to be asking about is really of no use as long as you don't remove the crankarm. It's only used to get the crankarm into the proper position before the bolts are tightened. I don't recall ever seeing a Hollowtech crank, so I can't say if they are the same or not for what this fastener does.

Also, we are talking about the left side aren't we? There isn't one for the drive side.