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Swapping Cassette Cogs?

Old 03-31-17, 08:13 AM
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hexron
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Swapping Cassette Cogs?

I have two Shimano cassettes - 12/27 and 12/25 - can I swap the largest cogs on these cassetes? I was using 12/25, but now live in hilly area and wondering if I can just bring the 27t cog over to the 12/25 cassette?
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Old 03-31-17, 08:29 AM
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You can't swap just the 27T for the 25T since the largest three cogs (21/23/25 or 21/24/27) are mounted together as a unit on a spider. You can swap the entire three cog assemblies from one to another.
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Old 03-31-17, 08:34 AM
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what speed cassette? on shimano the last 3 are riveted together in 11 speed, with that said, you can swap the whole last 3, and it works fine. I made a customer 12-28 this way from an 11-28 and 12-25. works great
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Old 03-31-17, 08:37 AM
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Originally Posted by ypsetihw View Post
what speed cassette? on shimano the last 3 are riveted together in 11 speed...
They are in 9-speed and 10-speed also.
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Old 03-31-17, 08:38 AM
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Originally Posted by HillRider View Post
You can't swap just the 27T for the 25T since the largest three cogs (21/23/25 or 21/24/27) are mounted together as a unit on a spider. You can swap the entire three cog assemblies from one to another.
It depends on the model of cassette.

Ultegra cassettes typically have 3 together on a spider.
Dura Ace I think has them in pairs.

Other models, Sora, Tiagra, etc, typically have a bunch of sprockets riveted together. You can safely remove the rivets and deal with the sprockets individually.

Shifting may not be quite as smooth with the larger jump, and possibly mis-aligneds shift gates, but it should work.

If adding more teeth to the cassette, double check your chain length, big front ==> big rear.
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Old 03-31-17, 10:49 AM
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Originally Posted by CliffordK View Post
It depends on the model of cassette.

Ultegra cassettes typically have 3 together on a spider.
Dura Ace I think has them in pairs.

Other models, Sora, Tiagra, etc, typically have a bunch of sprockets riveted together. You can safely remove the rivets and deal with the sprockets individually.

Shifting may not be quite as smooth with the larger jump, and possibly mis-aligneds shift gates, but it should work.

If adding more teeth to the cassette, double check your chain length, big front ==> big rear.
I can't comment on Dura Ace cassettes having never ($$$) owned one. Ultegra and 105 9 and 10-speed cassettes do have the largest three cogs on a spider.
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Old 03-31-17, 11:02 AM
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Quite likely to work fine.
Swap three if you have to or just one depending on the cassette. Or why not the whole cassette?
Check the shifting before you ride it,limit screws and chain lenght etc
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