aaaarrgghhhh!!!! Chain rings don't fit.

[02GF74]

remember my friends bike, re: needing a tool for the bottom bracket?

well since I don't have the tool, I thought I just swap the chain rings over, both have 4 bolt on same pcd .. BUT although the holes line up, the little flat bit by the hole is longer on the new rings so they won't fit onto the cranks!!

FFS what is all that about?!?!?!

 

[Tim Bennet.]

Not all Shimano 4 bolt rings are interchangeable (despite what loads of bike shops will tell you!). Although the PCD is the same, (IIRC) the XT rings will not fit on spiders of LX or below, or others such as Race Face, because of the extra depth to the lug. (As you have found out!)