I have a 12-27 dura ace freewheel on my bike and wanted to shift to a 11t cog but the cog i bought slips badly and I am wondering if there is a different look nut needed to get this to work.
I am running a 10spd sram chain and xtr derailleur with the setup. The dura ace freewheel and chain are new as is the 11t cog.

Is there any reason this thing isn't working?

sorry if this has been addressed in the past I couldn't find any posts.

Ken

11T cogs need 11T lockrings....yes.

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Used to race....got too wrinkly and old Updated: Racing again! Thought this was unlikely! Eventually, I may even have a decent race!

Its the cassette you changed not the freewheel (which you don't have!)

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Impoverished weight weenie wanna-be!
Budget 26" HT build viewtopic.php?f=10&t=110956

yes indeed you are right the cassette! I have been also shopping for freewheels for another bike my mistake! I will search for a lock ring for 11t. Thanks for the info.

Ken

If all you're doing is taking off the 12tooth cog and replacing it with the 11tooth cog, there is one issue besides the lockring size. An 11tooth cog has a wider built-in spacer than other cogs. The extra width is intended to sit in the recess of the 12tooth cog. Without that, the spacing will be off, you may get chain noise in the 11tooth, shifting to the 12tooth may be poor, the chain may even rub your dropout.
Again, if the main goal is to get an 11tooth cog on there, keep the 12tooth cog and remove the 13tooth instead.