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Discussion Starter · #1 ·
I'm thinking of upgrading my 2005 Allez to 10-speed (already ordered shifters) and I'm considering cassette sizes. What I think I want is a little more on the top and bottom.

Currently the bike has 39/53 on the front and a 12/25 Shimano 105 9-speed on the back, with an Ultegra 9-speed rear derailer.

So what are the advantages/disadvantages of
1) 11-25, and just suck it up for the low end
2) 11-25, and switch to 38/53 on the front. (not much ratio change)
3) 11-26
4) 11-26 with 38/53
5) 11-27
6) 12-27, and learn to pedal faster
7) 12-26
8) 12-26 with 38/53

Complicating things, it looks like only SRAM makes any of the above but 12-27, though I've read the Shimanos can be modified by adding an 11T.

I'm leaning towards 11-26 (with the idea of 38T front held in reserve if I need a little more hill climbing help).
 

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number 6

If you find your current 39/25 inadequate, then a 26 isn't a lot of help. One of the biggest advantages with 10 speed is gaining the 16T cog. Any 11-25 won't have that. Not many people really need a 53/11 unless they just can't spin. It only takes another 8 rpm to get the same speed with a 53/12.

Another option would be a 50/34 compact with an 11-23. You get most of the low gearing of the 39/27 and a little more top gear than a 53/12. That's what I'm using, but I climb and descend the Colorado mountains with it.
 

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ab aeterno
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If you want more on the top and bottom I think the best choice would be the 11-27 and keep your current chain ring, but I don't think there will be any difference between your highest gear and lowest gear in an 11-27 w/ 39/53 and a 11-26 w/ 38/53.
It's really more a choice about the gears in between and money.
 

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Discussion Starter · #5 ·
Thanks for the suggestions. I thought about compact, but didn't want to spend the extra money, and Pennsylvania hills are nothing compared to Colorado mountains. I'll probably try a few more rides with my current setup taking particular note of what I'm doing in top and bottom gear, then decide.
 
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