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Discussion Starter · #1 ·
I currently have a 12-25 6700 Ultegra Cassette and I ride in suburbia St. Louis where there are a lot of rolling hills but I am hoping some of you could help me if I were to change my cassette to something else. I usually ride 30-40 miles when I go out and climb around 1500-2500 feet each ride (nothing fancy) but I get a little slow around the last few hills. I like to keep a cadence around 90 rpm and can usually hold that in my 34-23 for most of the hills but get into the 34-25 setup for the others.

If I were to switch out to a 12-27 105 Cassette, would the 24 be closer to the 23 or 25 and would having the 27 give me a decent enough boost over the 25 if I get too tired to keep a 90+ cadence? I don't want to switch my whole setup to an 11 speed just yet and I don't really get enough speed to get into an 11 tooth cog for descents/flats that it is worth it to go that route.

Any thoughts?
 
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a 27 is about 8 % easier than a 25... not sure that is enough. Only you can answer that. I suppose if your cadence is staying about about 82 in those situations then it would work. I did make the same trade off as you though.. I gave up the 11 for more mid range and tighter jumps between gears.
 

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'brifter' is f'ing stupid
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I currently have a 12-25 6700 Ultegra Cassette and I ride in suburbia St. Louis where there are a lot of rolling hills but I am hoping some of you could help me if I were to change my cassette to something else. I usually ride 30-40 miles when I go out and climb around 1500-2500 feet each ride (nothing fancy) but I get a little slow around the last few hills. I like to keep a cadence around 90 rpm and can usually hold that in my 34-23 for most of the hills but get into the 34-25 setup for the others.

If I were to switch out to a 12-27 105 Cassette, would the 24 be closer to the 23 or 25 and would having the 27 give me a decent enough boost over the 25 if I get too tired to keep a 90+ cadence? I don't want to switch my whole setup to an 11 speed just yet and I don't really get enough speed to get into an 11 tooth cog for descents/flats that it is worth it to go that route.

Any thoughts?
Not sure how you'd expect anyone here to be able to answer this. Only you will know.
 

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Any thoughts?
I think if you want to get stronger you might be better off riding what you have. If you want to make climbing easier to maintain the cadence the 12/27 will be a noticeable change, but an 11/28 would be better, you might go slower though.
 

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Discussion Starter · #5 ·
I don't mind trying to get stronger in climbs by doing more hill intervals but I was just curious about others experiences if they ever changed from a 12-25 to either an 11-28, 12-27, or even a 12-30.
 

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'brifter' is f'ing stupid
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I don't mind trying to get stronger in climbs by doing more hill intervals but I was just curious about others experiences if they ever changed from a 12-25 to either an 11-28, 12-27, or even a 12-30.
Of course it will be 'easier', but how that works for you is anyone's guess.
 

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Matnlely Dregaend
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Technically the 24 is closer to 25 than 23, but by a meaningless amount. It is in all practical aspects in the middle of the two. If you're in good shape you shouldn't need the 27 unless you climb some big or very steep hills, but in these days of spinning (however we arrived at it, doped or not), some people may like the 27 on even moderate climbs. I never use an 11, so my travel cassette is a 12-28 (with compact chain rings), with which I have climbed some of the steepest and longest (paved) climbs in the world. If you're thinking about climbing on gravel then I think the 27 or 28 makes sense even in just hilly areas. At home, I live in a hilly area, and I typically ride single speed (not fixie) or compact with a 13-26 cassette (yes, Campy) for the straight block 13-19.
 

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Huge in Japan
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It's like a saddle or shoes, what works wonderfully for some not so much for others. I went from an 11-28 to a 12-27 (10 speed) in order to pick up the 16 tooth because 15-17 is my personal sweet spot (compact crank). I didn't notice a huge difference between the 27 and 28 but I did notice it. Going from 28 to 27 and dropping the 11 was justified by picking up the 16. Right now I am on a 12-25 where I replaced the sprocket unit assembly with one from an 11-28 so I am on a bastardized 12-28 so now I have the 16 as well as a 28 bail-out. I love it and can see myself sticking with this set up. I found my way here by trying things and sticking with what I like for me.

I certainly believe that you will notice the jump from 25 to 27 but with that comes different incremental changes between other gears. Will you like it? I don't know but yes you will notice it.
 

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I don't mind trying to get stronger in climbs by doing more hill intervals but I was just curious about others experiences if they ever changed from a 12-25 to either an 11-28, 12-27, or even a 12-30.
Yeah, get the 12-27, or bigger if your derailleur has room for it.

Going from 25 to 27, your chain should be long enough. But check the big chainring - biggest cog cross chain combo before riding it: Shift to the big ring, middle cog, then have someone lift the bike by the saddle, and gently shift to the largest cog as you hand crank it. (If the chain is too short, it'll jam in this combo, causing some serious damage).

Climbing
On steeper hills, there's really no road bike gearing that will keep you pedaling in the 90 rpm range. (Except for triple chainrings for touring, with a very small third chainring).

But, even at low cadence, a bigger rear cog will let you stay seated and climb at slow speeds without excessive force from your legs.

Rear cog shifts change your cadence by anywhere from about 5% to almost 15%. It depends on the ratio between the two cogs. 13 to 14 is 14/13=1.08 or 8%, for example.

Examples:
34 front - 25 rear: It's been years since I had this as my easiest gear. I do switch out cassettes for long, very flat rides -- the 12-25 gives me close shifts on flatter roads to get the exact cadence I want, but climbs are harder, of course.

34 - 28
: This is 12% easier than the 25.
I can stay seated and climb at low speeds on longer 7% to 8% grades, at low cadences around 50 rpm. I only need light to moderate pedal pressure to keep climbing.

34-32: This is 28% easier than the 25.
Now I can sit on 10% to maybe 12% grades, going maybe 3.5 to 4 mph, still with reasonably light pedal pressure. This low gear lets me stand up and climb 15% to 18% grades without blowing up. I don't like the bigger gaps in cadence on flatter roads, but if the ride is very hilly, the low gears make a huge difference.

~~~
On moderate grades around 3% to 6%, I usually go to the lowest gear I have, to spin in the 90 rpm range if possible.

I did a very long climb, 12 miles & 3200 feet, with a consistent 5% to 6% grade the whole way. I mostly used the 34-32 and spun -- but my "spin" was mostly in the 70 rpm range. Occasionally, I'd shift 2 or 3 harder cogs and stand up, just for a break. (On the Storming of Thunder Ridge ride).
 
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