I wanted to replace my worn 90's chainrings so I bought a new crankset, but turns out the smallest cog on this one has quite a bit of inward offset (as opposed to the outward offset of the original one, pic 2) so it's hitting the chainstay.
I don't really see offset being listed as a parameter for 3x cranksets, so are all the new ones like this or am I just looking wrong?
What is the move then? Do I look for a BB with longer axle? I could maybe squeeze in a crankset with smaller cogs even if the offset is wrong, but I really want my 48t big ring to get some speed out of the 26" wheels.
by Nindzatrtl
5 Comments
Yes, you want a BB with a longer axle so the chainrings are in the same position.
Chainsets have specific BB lengths to give the correct chain line, they’re not always the same. You’ll need to install whatever width the new chainset recommends
BB with 122.5 (123) mm spindle
BB spindle length is too short. Grab a Shimano BB UN300 or Tange LN3912 bottom bracket in 68×122.5. You’ll also need a square taper bottom bracket tool, adjustable or 3/8 drive socket wrench, degreaser, rags, and fresh grease. I assume you already have a crank puller if you got this far.
Thanks for the replies! New BB it is then