Bicycle Mechanics - Custom Dura-Ace 11-27 Cassette?

Has anyone tried to do this by combining an 11-23 with a 12-27? I'm considering doing this to get greater range. Any thoughts or experts out there?

Thanks in advance!

You'll need your 11 and 12 from your 11-23 (the 12s are not the same). Then pull out a couple of the middl gears. The top 3 (maybe even 4) gears of a 12-27 are on a carriar and can't be split out. I've done something similar for extreme hill climbs. I'll take a 12-26 and slap on an mtb 28 cog taking out the 14.

Im no expert on this but if you already have the cassettes I would just measure the 11 (from the 11-23) and the 12 (from the 12-27) and make sure that THEY are the correct size. Of course the 12 on one is going to be different from the other since one is the one the lock ring touches and the other is loose. I have thought about this as well, and am interested in the result.

Do you need both the 11 and 12? How about buying a 11T top cog and just swaping it for the current 12T? You will lose the 12T but keep the close gearing below that. BTW, you will need an 11T compatible lockring too.

Assuming this is a 10-speed cassette, you will have: 11,13,14,15,16,17,19,21,24,27. The jump from 11 to 13 is pretty big but otherwise it's very close for the cogs you will use most of the time.

if you are looking for more gears for climbing, you won't be using the 11 or 12 much anyway. on one of my custom jobs i start with a 13 which allows a 23-26-28 on the top.

I'm going to talk to the mechanics at my LBS tomorrow to see what they say can be done. I'll let you all know what they say.

I'm going to talk to the mechanics at my LBS tomorrow to see what they say can be done. I'll let you all know what they say.

Uh ... didn't we just tell you it could be done? Kinda the whole point of this forum.

As you know, the teeth on the sprockets on a cassette need to line up in a precise pattern to make the shifting work. Therefore, you can't just take a sprocket from one cassette and put it on another. There are substitutions that can be made, but you need to be aware of this.

I have this vague memory of reading about this on the Sheldon Brown website, you might look there.

As you know, the teeth on the sprockets on a cassette need to line up in a precise pattern to make the shifting work. Therefore, you can't just take a sprocket from one cassette and put it on another. There are substitutions that can be made, but you need to be aware of this.

I have this vague memory of reading about this on the Sheldon Brown website, you might look there.
All makers have their cogs "keyed" so they can only go on the freehub body one way (well, they can go on flipped over but that's easy to avoid). That way the shifting ramps and shaped teeth automatically line up properly. If you use the same maker's cogs throughout, you can mix and match at will.

if you are looking for more gears for climbing, you won't be using the 11 or 12 much anyway. on one of my custom jobs i start with a 13 which allows a 23-26-28 on the top.

Exactly. If you need a 27 gear, you are climbing. There's no way someone resorting to a 27 needs an 11 at the other end.

If your riding varies that much, consider two different cassettes.

I see. I was really just looking for a "do it all" cassette since I do ride a decent mix of terrain.

As I understand it, you have to change the chain whenever you change the cassette (or something like that). Does everyone have a separate chain for each cassette they own then?

Also, I didn't get a chance to stop by my LBS today. I didn't mean to insult anyway by saying that I would go and ask there as well. I just figured that was where I would buy the parts anyway. I would have to explain to them when I got there to make sure I got the right parts.

Hey... I just read that SRAM has an 11-28! Anyone know if that is compatible with Shimano DA?

All makers have their cogs "keyed" so they can only go on the freehub body one way (well, they can go on flipped over but that's easy to avoid). That way the shifting ramps and shaped teeth automatically line up properly. If you use the same maker's cogs throughout, you can mix and match at will.

Shimano/SRAM cassette cogs CAN'T be flipped over. The wide spline is offset so that you can't.
Shift ramps ARE designed to be used with specific adjacent cogs.
A 14T cog used in a 12-14-16 combination IS different then a cog used in a 13-14-15 combination.
That said, sometimes it doesn't really matter.
I made up a custom cog with 12-17 spaced at 1T increments. Each adjacent cog is a mismatch, but since they are only 1T apart, they shift far better then the "matched" cogs did with their 2-4T differences.

I think at least "some" Free Wheel cogs could be "flipped".
Sheldon's site appears to be down the last couple days. Sure hope it's not permanent!:(

As I understand it, you have to change the chain whenever you change the cassette (or something like that). Does everyone have a separate chain for each cassette they own then?

Nope, assuming all parts are not severely worn. If you change your chain at the proper time you should be able to get 3-4 cycles before needing a new cassette. If your terrain really varies that much that an 11-27 is your ideal, you might want to consider a triple.

Shimano/SRAM cassette cogs CAN'T be flipped over. The wide spline is offset so that you can't.
Hey, you're right! I just checked a couple of cogs and the wide spline/narrow spline configuration makes it impossible to put the cogs on incorrectly.


Shift ramps ARE designed to be used with specific adjacent cogs.
A 14T cog used in a 12-14-16 combination IS different then a cog used in a 13-14-15 combination.
That said, sometimes it doesn't really matter.
I tend to go along with the "it doesn't really matter" approach. I've added out-of-sequence interior cogs and made substitutes at both ends of several 8 and 9-speed cassettes and they all shifted as well as the factory configurations.


I think at least "some" Free Wheel cogs could be "flipped".
Sheldon's site appears to be down the last couple days. Sure hope it's not permanent!:(
Old Sun Tour freewheel cogs could be flipped and that was a way to get more life out of worn teeth. Sheldon's site was back up a few minutes ago when I used it to find a component reference.

Hey... I just read that SRAM has an 11-28! Anyone know if that is compatible with Shimano DA?

A 10-speed SRAM cassette should be compatible with a 10-speed Shimano drivetrain, some say they are as good as Shimano, some say they're not.

The problem with wide range cassettes is you have to give up better cogs somewhere on the cassette to make room for the wider range end cogs. I would rather have a 12-27 or 13-28 than an 11-27 or 11-28. The problem with a wide range cassette is that the cog you need may be the cog that is missing from the middle of the cassette. And the truth is that most riders will be coasting at speeds where an 11 could work. If you want to go faster turn the cranks at a higher cadence.
I've put together several custom cassettes like 13-26, 13-27, 13-28, 14-28 using various combinations of cogs from extra cassettes and by buying individual cogs. But it's often more cost effective to buy a complete cassette if it's what you need.

Al