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Old 01-03-20, 01:36 PM
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Switch 11T Sprocket To 12T Shimano 8 Sp

I haven't had to make any mods on a Shimano cassette in almost 10 years. I did a bunch of web searches and didn't find any answers on Shimano small sprocket dimensions.

ThermionicScott, CliffordK

You guys have posted a lot about changing Shimano sprockets, maybe you can answer my question?

I'm finishing up a new build and I want to change the small sprocket on a NOS Shimano CS-M737-1 11-30T 8 speed cassette from 11T to 12T.

I have NO NEED for a 118" high gear.

I'll be running 48-34T chainrings and new Dia-Compe ENE ratchet levers with a 9 speed KMC chain so no indexing.

The 11T on the NOS cassette is 5.5mm wide/thick. I have some NOS 12T sprockets that are 4.5mm and 5mm wide. Is there a chart or listing of Shimano small sprocket widths???

The 11 speed lockrings are ~35+mm and the 12mm and up lockrings are ~38+mm. I'm all set there. Also I have a 1.1mm thick spacer that I could use with the 4.5mm 12T sprocket.

Any problems with using the 5.5mm 12T sprocket? I'll rarely be using it and the 12T should run a little smoother that the 11T one.

BTW, the Dia-Compe ENE levers have a smoother ratchet mechanism that the old Suntour Power shifters but are nowhere near as robust in construction.

The barrels are 20mm with a special design feature that allow them to work with 9 -10 -11 speed RDs.


Last edited by verktyg; 01-03-20 at 01:39 PM.
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