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Discussion Starter · #1 ·
Greetings,

I have an Ultegra Di2 Groupset and have on order a Dura Ace C24 Wheelset. Because I don't want to strip the cassette from my current wheelset I'm going to purchase another cassette. My current setup is a Hollowtech-II 50/34T crankset, 10-speed chain, 12-28T cassette.

I don't want to change the crankset but this is the opportunity to change to a different cassettes (if t's an improvement) for my setup if it could better my speed, save some legs and/or make climbing a little better.

I'm not familiar with gearing much at all.

I ride county roads with some hills, some can be a bit steep. I'm looking for gearing that can shift well and has is at the sweet spot between flats and hills. I'm currently at 220lbs.

With what you recommend what else would I need to change and the Di2 must be able to be adjusted to accept the change.

I see a lot of 12-25 and 12-30s but not many 12-28s

Thank you in advance.
 

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They all shift well. Determining what you need depends on the answer to some questions.

Do you use the 28 now? If no, you don't need it. Get the 12-25.

If yes, do you ever feel like you'd like to have an even lower gear? If no, get a 28 again. If yes, get a cassette with a larger largest cog.

That's it. It's really just math.
 

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Unless the hills are long and above 10% gradient I would probably get 12-25. If you have climbs of moderate length above 10% 12-28 and if those hills extend more miles perhaps a 12-32. 32 would also come in handy if you are climbing on gravel. Based on how you describe your roads a 28 ratio sounds about right. If you go for easier gearing it comes at the expense of close ratios, so anything you do is a compromise.

The wheels and the DI2 set-up aren't really a factor in the decision process. If you are stronger or weaker than average you may want to adjust the recommendations. Personally i find the easier ratios sometimes work against you in that you have to pedal way to fast to get up that hill and for me sometimes a harder gear results in a faster climb, unless you are dealing with a ventoux type scenario which means you can't fight the climb and have to go at a pace that simply conserves energy.
 

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I went thru a similar situation years ago...If you're getting over the climbs OK, I'd say keep the 12-28. If not, try a 12-30. If you're figuring on dropping some weight, your climbing will drastically improve. I've been slowly gaining weight from 160 up to 195 and my climbing has been a struggle. I dropped down to 170 over last winter and wow what a nice improvement I've seen this year. If you're able to drop any significant lbs., then you can reward yourself with a 12-25 and get the tighter spacing. Ride Hard!
 

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I went thru a similar situation years ago...If you're getting over the climbs OK, I'd say keep the 12-28. If not, try a 12-30. If you're figuring on dropping some weight, your climbing will drastically improve. I've been slowly gaining weight from 160 up to 195 and my climbing has been a struggle. I dropped down to 170 over last winter and wow what a nice improvement I've seen this year. If you're able to drop any significant lbs., then you can reward yourself with a 12-25 and get the tighter spacing. Ride Hard!
Good points. Dropping body weight and getting stronger legs matter far more.
What's Merckz? Ride up grades. don't buy upgrades.
 

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I ride county roads with some hills, some can be a bit steep. I'm looking for gearing that can shift well and has is at the sweet spot between flats and hills. I'm currently at 220lbs.
You haven't really explained your type of riding very well. "Some hills" and "a bit steep" doesn't tell very much. A bit steep to one person isn't steep at all to another. It's better to give max grades of the hills and how much elevation you climb over the distance you ride.

Really more importantly, what do you (or don't you) like about the 12-28? Do you feel like you need more gears to get over the hills?

With what you recommend what else would I need to change and the Di2 must be able to be adjusted to accept the change.
Technically a 28 is the largest cassette you can run with your rear derailleur. If you want to go larger, you might need a new RD. And that's where you may be screwed. The don't make the 10sp di2 RD anymore. If you happen to find one, you're going to pay A LOT for it.

That being said, you can usually go a little larger on the cassette that what Shimano specifies. It all depends on your specific frame and the only way to know is to try. I just put a 30 on my GF's di2 10sp and it works fine. In fact I think I could get a 32 on it.

I see a lot of 12-25 and 12-30s but not many 12-28s
11-28's are more common. Also look at both Sram & Shimano cassettes. They offer different ranges and both work.
 

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You haven't really explained your type of riding very well. "Some hills" and "a bit steep" doesn't tell very much. A bit steep to one person isn't steep at all to another. It's better to give max grades of the hills and how much elevation you climb over the distance you ride.

Really more importantly, what do you (or don't you) like about the 12-28? Do you feel like you need more gears to get over the hills?

Technically a 28 is the largest cassette you can run with your rear derailleur. If you want to go larger, you might need a new RD. And that's where you may be screwed. The don't make the 10sp di2 RD anymore. If you happen to find one, you're going to pay A LOT for it.

That being said, you can usually go a little larger on the cassette that what Shimano specifies. It all depends on your specific frame and the only way to know is to try. I just put a 30 on my GF's di2 10sp and it works fine. In fact I think I could get a 32 on it.

11-28's are more common. Also look at both Sram & Shimano cassettes. They offer different ranges and both work.
yep, anything bigger than 28 probably requires a long cage r.d. although shimano tends to be conservative and with 9100 coming out in maybe less than a month you might be able to use a 12-30 cassette or simply use a 3rd party supplied unit.

I have a compact with a 12/32 on my gravel bike with a compact up front. I honestly don't see it as some panacea for climbing.
 

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Steep hills? 11-32 is your ticket, spin baby, spin!


Yes, I would get the 11-32T. But IF, and only if your RD is a medium cage (GS). The short cage version (SS) will only handle up to a 30T cog. In that case, you would need to go with a 12-30T as there is no such thing as an 11-30T.

IMHO, I'd rather have the available low hill climbing gear available even if I don't usually need to use it. There will be the occasional "off day" where I will need the extra help. Unless you are racing or doing crits, you really don't need the close spacing of an 11-25T on an 11-speed cassette.
 

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Are you sure it is a 12-28 and not an 11-28?

This is brushing up against "what saddle should I get" especially with such scant information. It really is about what suits you best personally and will not necessarily be the same as what suits someone else best. For example I have a bike that came with an 11-28 which is a great range for me and my terrain here in the Southern Tier of NY. However I spend so much time in the 15-17 cog range that it made sense to me to move one tooth from the 11 and one tooth from the 28 to pick up the 16 tooth with a 12-27. Sometimes I miss the 11 but not very often and I rarely miss the 28, it was worth it to close the gap between the 15 and 17. That cassette has my personal sweet spot covered and a range that suits me.

Someone else might not feel the same way. We can help some here but we need more details about you, your area, what you like about your 12-28 and what you feel like you are missing with it.
 

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10-speed, right?

With a 34 in front you might find that you can still climb anything comfortably with 25 in the rear, so 11-25 would be a good option then...
 

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12/25 is very nice for having small steps between the lower gears. I would try not using your 28 on your steepest / longest climb and see how you do. If you can manage it not using the 28, go for the 12/25 would be my suggestion. I was quite surprised how easy it was to move to the 12/25 when I did it, you might be too. You can always throw the 28 on there if needed for routes outside your area with steeper or longer climbs.
 

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Go with an 11-21, but make sure that you have a 39 little ring, and not a 42, or 44.
It'll be fine.
 

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I don't think you can pick a cassette without saying something about what kind of cadence you use. I spin really fast, like 110 most of the time. As a result I use big cogs sprockets. 11-28 on my 11 speed, 12-30 on my 10. Both are compact 50-34 up front.

On the other hand if you grind down in the 80s, then sure, 11-25 is fine. It wouldn't work for me though.
 

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Discussion Starter · #16 · (Edited)
I'm trying the 11-28. I expected to be out of town longer but got in last night. I rode the 12-28 last night and felt I was missing something in the middle. My Dura Ace c24s arrived. I placed the 11-28 on that rim. If work
permits, I will take it out for a spin.

Side note: tried to move up from 25mm Tires to 28mm. No go. Rubbing - bummer.
 
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