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Old 04-29-07, 11:14 PM   #1
CaptDon
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Changing 12-25 Cassette to 12-27

I've got a Trek 2.1 Pilot with Ultegra 10 speed system. I would like a litle lower gear and would like to install a 12-27 cassette. Any problems with going to a slightly larger 27 tooth cassette? Would it be a simple cassette swap?

Thanks,

Don
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Old 04-29-07, 11:16 PM   #2
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I went from a 11-23 to a 12-27 without any issues. I just swapped the casettes myself and it worked easy. The only thing needed is the special bolt to unlock the casette from the hub.
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Old 04-29-07, 11:19 PM   #3
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Thanks......already have the tools for the job, just wanted to make sure. Did you notice much of a difference in low gear?

Thanks,

Don
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Old 04-29-07, 11:19 PM   #4
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I think the Ultegra derailleurs are designed to handle 27t and can be tweaked to handle 28t.
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Old 04-29-07, 11:22 PM   #5
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Yes, however, you might need to lengthen your chain depending on how much slack there is already.

If the chain does indeed turn out to be too short, you would just need to add a link.

http://bikeforums.net/showthread.php?t=266045

That is a link to a question I posted concerning something about the chain that should give you and idea of how long the chain needs to be - you can pretty much tell if your chain is off when everything is adjusted correctly and the chain still "auto-shifts".
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Old 04-30-07, 08:20 AM   #6
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Very unlikely that you would need to adjust the chain length. Just check the big to big combination to make sure the rear derailleur doesn't "bottom out".

Al
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Old 04-30-07, 02:16 PM   #7
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Quote:
Originally Posted by CaptDon
Thanks......already have the tools for the job, just wanted to make sure. Did you notice much of a difference in low gear?

Thanks,

Don
For me it made a huge difference since I went from a 23T to a 27T. I live on top of a 10% hill so it was a god send. I don't notice the gain of one tooth from 11T to 12T, although I suppose I could just mix and match from the casettes to make a franken casette. I'm not that concerned though.
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Old 05-01-07, 07:20 AM   #8
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What I liked about the change from 25 to 27 was that I almost never get off the 39 ring on my 53-39-30 triple, and I live in the hill country of central Tejas!! When I do go to the 30, it is some hill!!
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