TransWikia.com

Chainline issues

Bicycles Asked by Erik van Raalte on July 22, 2021

When my 10 year old chain snapped, I realized that I needed to replace my rear cassette and crank, due to wear. Noted for the future! I ordered a 9 speed cassette from Shimano (same brand and number of gears as I had), and a 3 speed front crank (again, same amount of gears and same brand, different type though: Shimano Altus M371). I thought I had taken all the factors into account, but of course I was wrong :). I noticed that I could not adjust my derailleur to smoothly shift gears without rubbing. I didn’t know about the concept chainline, and I think it is very likely that my new crankset has a different chain line (50 mm) than my old one (unknown).

The problem that I have is that I can’t find what chain line my old crank had. I think my options are either:

  1. find out what chain line my old crank has, and try to find something similar. -> This seems very difficult, because most cranks I can order have 50mm (the same as the one I just bought)
  2. play around with spacers. I am afraid this gets me into a rabbit hole. I don’t exactly know what I need and I am afraid I will ruin something when I have to dissassemble my bottom bracket.

A picture to give it a little bit more context:
Situation with new crankset

Is this the moment to go to a bike shop? Or is there an easy fix that I could apply? I have a three piece crankset (I think it is Shimano Octolink).

One Answer

You have a square taper bottom bracket, which means there are no spacers that can help you. What you need is a bottom bracket with a longer spindle. Shimano recommends a BB-UN300 with a 123mm spindle for your crankset, so that's what I would get. Don't be afraid of changing your bottom bracket, it's not a complicated procedure and there's not really anything you can damage if you're careful and not cross-thread the BB into the shell.

enter image description here

Correct answer by Victor Stanciu on July 22, 2021

Add your own answers!

Ask a Question

Get help from others!

© 2024 TransWikia.com. All rights reserved. Sites we Love: PCI Database, UKBizDB, Menu Kuliner, Sharing RPP