So, I've bought the wrong shimano splined bb. I went for 118mm axle, finally got my old knackered one out today and it's 121mm. What are the possibilities of using the 3mm shorter one, or is it back to Merlin for the right one? (They only had 118 or something shorter on the site, so went for the one the looked closest- whoops)

Morning bump before I package up the 'wrong' bb to return to Merlin……….

1.5mm shouldn't make a difference unless it's got a poopy chainline at 118, the extra 1.5 might throw it off.

I don't know for sure either.

Depends on your cranks and how much clearance they have/don't have with the BB shell along with chainline – as cynic-al says.

If in doubt I'd order a 121 today from wherever and send the 118 back for a refund from Merlin 🙂

Morning Tom,

Are you at work today as im off and i could have a quick look before you decide what to do…However, i can`t see 1.5mm either side making a lot of difference.
😉