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Discussion Starter · #1 ·
I am building a new bike and am switching from an FSA Compact 50/34 12/25 to a Cannondale SI 53/39. I want to keep my climbing gears but also do not want to spin out on downhills. I feel as if I need an 11 gear on the low end, but don't know if the 23 will give me enough for climbing? I looked for an 11-25 and can only find a junk Token cassette. People have told me about switching out the drive unit in my wheels to a shimano compatible but I use a Campagnolo wheel and cannot do that. If anyone can tell me what my best fit would be to mirror the compact crank, I would geatly appreciate it.
 

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equivalent gears...

With a campy equipped bike, this is a simple one. Your top gear is only slightly moe than 53/13 and your low is like a 39/29, so you need a 13-29 cassette with a medium cage rear derailleur. Use the formula: 12/50 x 53 = 12.72 to get these equivalent gears.


Actually, many campy wheels can be changed to a shimano-compatible cassette body (made by campy), but it's not cheap. If you got a Shimano 12-27 cassette, the cog spacing isn't the same and shifting would suffer some. You would have more top gear, but one less climbing gear.
 

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Discussion Starter · #3 ·
Thanks, but i'm still confused. I have a short cage rear derailleur though and never get in to my 25 cassette. A 13/29 seems like way too much climbing gear and not enough low end for downhills. Seeing that my chainrings are bigger now, shouldn't I be gaining climbing gears on the big chain ring and losing power gears on the small which would mean a smaller cassette like an 11-25?
 

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you're confused...

vegasracer99 said:
Thanks, but i'm still confused. I have a short cage rear derailleur though and never get in to my 25 cassette. A 13/29 seems like way too much climbing gear and not enough low end for downhills. Seeing that my chainrings are bigger now, shouldn't I be gaining climbing gears on the big chain ring and losing power gears on the small which would mean a smaller cassette like an 11-25?
Maybe it's you terminology that needs a bit of help. The big ring is not for climbing, it's for descending (high speed, not low speed). You said you had a 34/25 lowest gear, but you failed to say that you never used it. To compare your current climbing gears, the 34/21 is like a 39/24, or not quite as "low" as a 39/25 and your current 34/23 is like a 39/26, so it's a bit lower. You don't have a gear ratio that's just like a 39/25.


You said you want to retain climbing gears, the lowest of which is the 34/25. If you don't ever use this lowest gear, then about the only other option is to use the same 12-25 cassette. In this case, you'll suffer a pretty significant loss in climbing (low) gears, but you'll gain top end for the descent with the larger big ring.


As for the top end (high speed), do you spin out now? The 53/13 that is closest to your current 50/12 only requires 2-4 more revolutions per minute (of the crank) to produce the same top speed. If you spin out now, then by all means stick with the 12-25.
 

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Juanmoretime
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jeremyb said:
KCNC warrantees their scandium cassettes to last for 6000 miles. And they are very light.
I have about 5,000 miles to go to test KCNC claim on mileage but to date it's been an excellent cassette. Shifts extremely well and the chain runs so very quiet over the alloy cogs.
 
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