Cassette Cog Interchangeability
 

I have two 9 speed cassettes: one is a SRAM PG-970 11-32 cassette, the other is an Ultegra 12-27. The 12 tooth cog on the Ultegra is missing and I would like to use the 12 tooth cog from the SRAM. They look compatible to me but I know nothing about the issues involved.

Will this substitution work okay?

Should work fine. If there is a problem it will be immediately obvious when you put it together.

Sheldon "Go For It" Brown

Thanks Sheldon, I will try it.

When mixing SRAM road and MTB cogs, I ran into shifting problems that could be attributed to different profiling of the cogs. The chain needed to be relatively offset by a minute amount for the two types to shift properly. (This could be compensated by spacer thickness.) However, for the first cog, the shifting is regulated by limit screw, so there should be no such type of problem.

The only thing that comes to mind is whether the ramps line up between the two brands.

For what it is worth, I put the SRAM 12 on the cassette and it fit fine. Unfortunately, I could never get it to work correctly. Took it to my LBS and they could not make it work either. Don't know why but the result was the bike would never shift into the 8th cog, it would always jump over it going up or down, to or from the 12. Took the 12 off and put the 30 back on and everything works fine.

The 12 from a cassette starting with an 11 is not a first position cog and has no built-in spacer. It won't work as a first position cog on your 12-27 if that is what you are trying to do.

Al