Why would one ever buy a 12-25 cassette when an 11-25 is available?

  • I was looking at purchasing a new cassette and chain. Looking at the available cassettes for SRAM components, there is a big variety of sizes available:

    • 11-23: 11-12-13-14-15-16-17-19-21-23
    • 11-25: 11-12-13-14-15-17-19-21-23-25
    • 11-26: 11-12-13-14-15-17-19-21-23-26
    • 11-28: 11-12-13-14-15-17-19-22-25-28
    • 11-32: 11-12-13-15-17-19-22-25-28-32
    • 12-25: 12-13-14-15-16-17-19-21-23-25
    • 12-26: 12-13-14-15-16-17-19-21-23-26
    • 12-27: 12-13-14-15-16-17-19-21-24-27
    • 12-28: 12-13-14-15-16-17-19-22-25-28
    • 12-32: 12-13-14-15-17-19-22-25-28-32

    Now I can understand why someone would choose a cassette based off of how many teeth the big gear has. Some people live in hilly or mountainous areas and desire a higher number of teeth. Some people live in flat areas where they simply won't use those cassettes with a lot of teeth on the big gear.

    But why would anyone ever choose to buy a cassette with 12 teeth on the small gear instead of 11? 11 teeth = higher maximum speed. I doubt many people buying a nice set of components (Shimano, SRAM etc) would ever say "I don't need to go faster so 12 teeth is fine with me."

    What's the point of 12 teeth when you could opt for 11 instead?

    The 12-25 gives you one more cog in the middle of the range, where you'll spend the most time and hence most want to "optimize".

    @DanielRHicks - exactly right. I have an 11-25, and I find I very often have a "gap" where a 16 fits perfectly. I can find the number of times I've used the 11 on one hand with a couple fingers and thumb left over.

    With this many cogs in the back, do you still have a front derailleur?

    I've got an 11-23 and it wouldn't matter if it started at 12... The 11-12-13 are too crossed over on the small front chainring and on the big front chainring I don't get past 14 or 15 ever anyways. :-)

    So far I've used 12-26 (which got me up the steepest Scandinavian mountains with luggage), though I wouldn't have minded an even lower gear. Now that replacement of the cassette is due again: I'm trying to find the 12-27 you quote - but can't. Do you have a link to SRAM or a supplier with that spec?

    @BrianKnoblauch It sure sounds like that 11-23 does not work so well for you in that bike; you might enjoy a set of cogs that in fact tops out at 14.

    Not an answer but a confirmation - I've just taken 11 - 25 OFF my Roubaix Pro for an Ultegra 12 - 25 for the mid range on bike tech advice. Used the 11 half a dozen times in 5 years, and never where I am now (Guernsey)

    I'd rather carry around an 11 tooth cog and rarely use it, than spin out in a decent tailwind.

    @Criggie 53x12 gets you 40+ mph at 120 RPM. What kinda winds you riding in? ;-)

    @AndrewHenle that'd be awesome - but its 44:11 max gearing which is 35.5 mph at 120 RPM (57 km/h) and given its a bent, 90RPM.

  • If you want to maximize your max. speed, go for an 11 tooth cog. If you want to maximize your average speed, unless you're a pro you probably are better off without it. Even cruising at 40km/h does not require and 11 tooth cog.

    For example, take a look at this table, showing cruising1 speeds for a 11- 21 tooth cassette: cruising speeds for a 11- 21 tooth cassette

    And compare to this table for a 12 - 25 tooth cassette:

    cruising speeds for a 11- 25 tooth cassette

    You can see that the 11 tooth cog is only really useful for cruising speeds that riders at the professional level can maintain, or for short bursts. So, like I said, if you aren't trying to break your own max speed record, you may be better off with a 12 tooth cog.

    (Tables screen captured from bikecalc.com. Check it out.)

    I remember reading a while back about how most riders can't maintain a high enough wattage output to make an 11 tooth cog worthwhile, but I couldn't turn it up. Maybe another contributor will post it.

    1 Cruising here means pedalling at 90 r.p.m.

    "You can see that the 11 tooth cog is only really useful for cruising speeds that riders at the professional level can maintain, or for short bursts." This of course assumes flat terrain. People who live in mildly hilly areas might find themselves frequently cruising at a higher speed. It all depends on where you live and how you ride.

    Is the row along the top the number of teeth in the front chain ring?

    Yes, although practically you are very likely to be in a chainring with either 50 (compact crank) or 53 (standard) teeth while using a 12- or 11-tooth cog.

    It's all relative to the wheel size, crank length and front chain ring! I put an 11-28 freewheel on my compact MTB. It has 24" wheels and a 48 tooth front ring. The 13-28 wasn't doing it for me any more (got to the point that I'm climbing some hills using the highest 48/13 combo), but 11-28 is about perfect. The 11 gives that nice impedance when I stand up to pedal, and less spinning on declines. If I build more muscle, I will have to go for a 50+ ring.

    @user973810, What is the units in the table. I'm assuming km/h given your usage of it preceding it.

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Content dated before 6/26/2020 9:53 AM