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I have a road bike with a 26/11 9 speed SRAM rear cassette. I cycle in Cambridgeshire on a daily basis and it's very flat. I find that I never use the hardest cog, leave the chainring on the biggest cog and generally find that the jump between gears is a little too much.

My chainring is a compact 50/34 110mm.

Sometimes it gets very windy and I'm forced to have to change to the smaller chainring cog - I guess that means I don't want the big cassette cog to be any less than 26 or so. I'm not a fan of changing between my chainring cog much as it kind of changes everything.

Ideally if it exists, I guess a 27/14 (do they exist?) or something similar would suit me better... not sure if 27/15 would cut my top speed down too much though.. I find with my current 28/12 I can get over 30mph without spinning out (with lots of room to play). I never go this fast unless I get an amazingly lucky tailwind :) There's no downhill here either!

Basically I have no experience of different cassettes so any guidance from an experienced cyclist would be of great help. I'd like to avoid buying something stupid.

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Note: Fast-ish that is. I probably average 18mph on my commute. I suppose the slowest top end of the cassette I'd like would be about 25mph. –  John Hunt Mar 14 at 14:08
    
You might want to go with a cassette with very fine spacing, like a 12-23, and then change your front chainring for a smaller one so that it's the equal to having a 15 on the back with the chainring you have now. –  Kibbee Mar 14 at 14:52
    
What front chainrings are you running? If you'venot got a compact double, consider it. I find the 50/34 gives me a really good range, and running a 12-23 would give you a closely spaced set of gears, but not much for climbing at all. –  7thGalaxy Mar 14 at 15:04
    
It's a compact double. Not sure on the count..I'll have a look after work and report back :) –  John Hunt Mar 14 at 16:04
    
I've added the correct counts now... looking at a shimano HG50 but worried it won't accept a normal chain? I keep reading the HG50 takes a super-thin chain of some type.. does that work with normal chainrings? –  John Hunt Jun 24 at 21:50

3 Answers 3

My guess is that if you have 12-28, you might not have a Shimano 9 spd hub. Generally Shimano road clusters top out at 27t. That sounds more campy-like to me. That's the first thing to figure out. Shimano and SRAM clusters are interchangable, Campy are not.

If you have a shimano hub, it's very easy to build 'custom' cassettes with Shimano 9spd parts. It's just not cheap. If you've got the tools to remove the cassette, you can get an 14-25

http://www.chainreactioncycles.com/us/en/shimano-tiagra-hg50-9-speed-road-cassette/rp-prod387

and mix and match with your current cassette to get the gears you want. It may be possible to do the same kind of mix/match with campy 9spd cogs, it's just more expensive. You can get 14-28 campy cassettes.

http://www.universalcycles.com/shopping/product_details.php?id=5047&category=40

If you can find them, junior racing cassettes are a good solution. Junior racers have gear limitations so they tend to have clustered but lower gears. Currently they only seem to be available for 10 speed cassettes, but you can get 16-27 cassettes.

If you poke around enough on the web, you can find small companies like IRD that will make all kinds of custom cassettes. They aren't cheap though.

http://interlocracing.com/cassettes_steel.html

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Good point on Campy. If you are running campy though, Jtek makes a pulley called a shiftmate that allows you to run campy shifters + derailleur with a Shimano cassette (but then you need the right freehub body (i think its Fulcrum RS-13 or something)). In any case, a bit of a Rube Goldberg solution (and about 110 dollars according to amazon). –  Batman Mar 15 at 0:03
    
There are definitely 9 cogs on my cassette - and SRAM is stamped on the lock ring. I didn't get a chance to count the teeth on my chain ring unfortunately. I am right in assuming 9 cogs on cassette = 9 speed right? I'm still new to a lot of this stuff. –  John Hunt Mar 17 at 8:54
    
Also it could well have been 12/27 and just me counting them incorrectly! I seem to remember double counting the smallest cog a few times but I wasn't so careful with the big one. –  John Hunt Mar 17 at 8:57

The first thing to note is that depending on the range of the cassette, you may need a different derailleur. Derailleurs come in different cages (short, medium and long - these are marked SS, GS, SGS respectively). These set your chain wrap capacity (and usually tell you what the largest sprocket you can run in the back is), and you can use a longer cage derailleur with a larger cassette (there is no harm in running a longer cage derailleur than you need, other than looking less cool). Luckily, if your derailleur can't take a larger cog in the back, you can just drop in another derailleur from either the road or mountain group of the same manufacturer (for example, if you're running Shimano, you can put a nice Deore SGS 9 speed rear derailleur on if you need a larger cog in the back and your current can't take it).

As for the smallest cog in the back, most people don't use it. It would be good if you specify what kind of spacing your current cassette has. I think for most people who aren't racing, the spacing of cassette that comes on touring bikes is probably adequate (e.g. Shimano HG-50 11-32), and just dealing with it. However, the spacing is probably too big for your liking.

Here is a list of cassettes - I think the "Harris Century Special" (a custom cassette) looks good, but it is pricey.

Also, Sheldon has a gearing calculator so you can put in some cadence you try to maintain and see what kind of speeds you hit at that cadence - the drop down has a set of standard cassettes.

As one of the comments says though, you may want to try changing your chainring spacing instead.

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Great answers! Thank you. I'll come back with more info when I get a chance but I very much appreciate both the answers I've been given thanks :) –  John Hunt Mar 14 at 20:23

The simplest change you can make is to swap your big front ring for a smaller one. If you currently have 34/50 on the front, change it to 34/44. Your easiest gear on the big ring would go from 47 gear inches down to 42 (and the hardest from 110 to 97). If your front shifter is indexed it might not shift as quickly, but it should be OK because it will be a smaller difference between the two rings.

For the rear cassette... If you want optimum gear choice for easy spinning, choose a rear cassette with close gear ratios, like the Shimano Tiagra 9-speed 14-25. It is compatible with SRAM 9 speed, and is available from Chain Reaction for less than $20 US. (SRAM does not offer a comparable close-spaced cassette.)

If you pick the 14-25 cassette you will probably want to go much smaller with your big front ring, maybe 40 or 42 depending on how big a top gear you need. I rode this cassette for a year with a 40t big ring (in my flat, windy area), and I never missed having bigger gears. As always, Sheldon Brown's Gear Calculator is a great help in making these decisions.

One last note is that none of the changes above would force you to change your rear derailleur, although you would need to shorten your chain (or get a new one).

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