my kids mtb on the smallest cassette cog the chain rubs on the next bigger cog creating a harshness while using this smallest cog. I was looking at it and the spacing between the two smallest gears seems to be smaller compared to the remaining gears on the cassette. My question is this normal? It is a Trek marlin and has never been apart since new. Thanks for any help in advance.
The cogs should be evenly spaced. On a normal Shimano HyperGlide type cassette the smaller cogs should have plastic spacers between them. It’s possible whoever installed the cassette forgot the spacer or installed it in the wrong place.
There are two exceptions:
- The smallest (11 teeth) cog usually has the spacer “integrated” into the cog, i.e. it’s thicker and doesn’t need one of the plastic spacers.
- The two or three biggest sprockets are often riveted onto a “spider” and don’t need spacers either.
Make sure the cogs are evenly spaced and are not loose. If a spacer is missing altogether the lockring probably can’t press against the cogs and the cogs will be loose and have play.