moving from a larger cassette to a smaller one
03-20-16, 12:43 PM
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moving from a larger cassette to a smaller one
Sorry for the stupid question: If I am moving from a 12-27 rear cassette to a 12-25 rear cassette, I don't need to change the length of the chain, correct? Reason being that if the derailleur can handle the 27, it can certainly handle the 25, and since the small cog (12) hasn't changed, I don't need to shorten the chain. Right? Your help is most appreciated.
03-20-16, 01:04 PM
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However, if you discover that your shifting is no longer accurate, you may want to take out the extra links anyway.
03-20-16, 01:06 PM
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& since you are putting a New cassette on , the chain is worn into the one you took off, so buy a new chain too.
bag your chain and cassette up together .
bag your chain and cassette up together .
03-20-16, 01:29 PM
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Since a large cassette incorporates the sprockets of a smaller one within itself, there's nothing to do when downsizing.
You MAY sometimes benefit from adjusting the B-screw to bring the RD up closer, but it's not necessary.
You MAY sometimes benefit from adjusting the B-screw to bring the RD up closer, but it's not necessary.
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03-20-16, 01:41 PM
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Shortening a chain by 1" may result in a too short of chain.
03-20-16, 02:19 PM
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Well, I was not assuming the original chain was the right length. If it was too long in the first place, that's when an adjustment might be needed. I've seen that a few times (including on my own bike, once!)
03-20-16, 02:25 PM
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If your theory about shifting getting bad because the chain is 1" too long, what in the hell would shifting be like on the smallest cogs?
03-20-16, 03:07 PM
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If the chain can handle the big-big combo without over-stretching the derailleur, as well as the small-small combo without dragging back across itself, then you're fine. Adjust as needed.
As fietsbob mentioned, replace the chain if it is not absolutely new.
As fietsbob mentioned, replace the chain if it is not absolutely new.
03-20-16, 04:58 PM
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A chain can't be too long, as long as it isn't slack and sagging on the small/small combination. Since just about all cassettes start with an 11 or 12t sprocket, if the chain wasn't sagging before it won't after.
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03-20-16, 05:18 PM
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All --
Thanks very much. This is very helpful. This is actually for a new bike. I ordered the 12-27 but I'm having second thoughts and want to be able to try out both. Not having to mess with the Campy 11 speed chain each time makes this a lot more feasible.
Thanks very much. This is very helpful. This is actually for a new bike. I ordered the 12-27 but I'm having second thoughts and want to be able to try out both. Not having to mess with the Campy 11 speed chain each time makes this a lot more feasible.
03-20-16, 11:55 PM
#12
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You can probably leave the chain sized for the 27T cog in case you decide to go that way later.
Since that MIGHT also be sized correctly for 25, nothing lost. If not, you're really pretty close and won't suffer shifting issues.
Since that MIGHT also be sized correctly for 25, nothing lost. If not, you're really pretty close and won't suffer shifting issues.
