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Old 07-26-05, 06:40 PM   #1
veneer
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quick cassette question...

i'm currently running 12-25 in the rear with 53/39 in front. my question is... if i were to change the rear to 12-27 (for climbing hills) then will i have to adjust anything on the rear derail.?

also, is there a big difference between 12-25 vs. 12-27 in climbing? i know that the only difference between them is the last 3 largest cogs, so can i just purchase that part only instead of the whole cassette? if so, where can i buy it from?
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Old 07-26-05, 06:52 PM   #2
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Originally Posted by veneer
i'm currently running 12-25 in the rear with 53/39 in front. my question is... if i were to change the rear to 12-27 (for climbing hills) then will i have to adjust anything on the rear derail.?

also, is there a big difference between 12-25 vs. 12-27 in climbing? i know that the only difference between them is the last 3 largest cogs, so can i just purchase that part only instead of the whole cassette? if so, where can i buy it from?
You may have to adjust the B tension screw. The chain is probably long enough,but be sure you can shift to the big/big without ginking anything.If cogs or groups of cogs are available,they will be in the QBP or special order catalogues at www.harriscyclery.com You can do the math on the % difference in gear inches better than Barbie can....maybe.
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Old 07-26-05, 07:51 PM   #3
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Here is a site that advertises the cluster you are looking for, but at that price plus shipping you could probably buy the entire cassette:

http://aebike.com/site/page.cfm?Page...and=367&type=T

Only the two largest cogs are different from the 12-25 cassette.

You will feel the difference between a 25 and a 27. Whether or not the difference is enough depends on you and the hill.

Al
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Old 07-26-05, 08:06 PM   #4
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You will feel the difference between a 25 and a 27. Whether or not the difference is enough depends on you and the hill.
Well said.

veneer: you have any specific local hill(s) in mind?
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Old 07-26-05, 09:19 PM   #5
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I would readjust the rear derailer after changing cassettes, even if the size is not different. This is probably not necessary, but a quick realignment only takes a few minutes, and I've found it really helps with the shifts.

It's also really easy to do, hit up parktool.com if you need how-to info. Learning to do it yourself is well worth the time.

As far as 25 vs. 27, it's not going to be a huge difference. If you are just barely unable to spin your 25, then the 27 will probably do it for you. But, if your legs are totally giving out on steep climbs, and you do a lot of them, then I would possibly consider a compact crank.

For reference, I use the compact early in the season, and have found that it helps especially on hills that have long sections above 10% grade. Anything else than this and I can spin the 39x23 or higher gearing just fine.
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Old 07-27-05, 12:42 AM   #6
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actually i haven't done much of the crazy hills. but on some of the hills.. i end up mashing it instead of spinning it, which cause my legs to give out. perhaps i'll just stick with 12-25 and keep grinding at the hills.. till my legs gets stronger.
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Old 07-27-05, 04:08 AM   #7
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Originally Posted by veneer
actually i haven't done much of the crazy hills. but on some of the hills.. i end up mashing it instead of spinning it, which cause my legs to give out. perhaps i'll just stick with 12-25 and keep grinding at the hills.. till my legs gets stronger.
Then you'll need new knees.
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Old 07-27-05, 11:10 AM   #8
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operator.. yeah i know.. that's why i'm trying to learn how to spin on the hills instead of mashing. especially after ever ride at night, i use icy hot to rub my left knee and wrap it up and go to bed. it's not like super paiinful... but gets annoying afterwards.
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