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.

  • For me, and for many riders that come through my shop, the 11-25 is missing the critical 16t cog, which (at least for me) is the sweet spot. That is, the gear which I don't tend to spin out of, and that doesn't turn in to a grind fest.

    If I'm doing a Euro trip, then I will run an 11-28, with a compact front. But at home, for daily riding, a standard 53/39 with a 12/25 is perfect.

    For what it's worth, the 11t cog was designed to give a compact crank, with its smaller front range, the same or similar top speed as a "standard" setup, which at the time was a 53/12 maximum.

  • Some people will never get the chance to use the 11 teeth setting, whether this is through not being fit enough or another reason.

    So they can opt for the slightly longer expected lifespan of the 12 (lower wear per tooth) and the slightly narrower gap between ratios which can make gear changing less of a struggle.

    You can compensate for the lack of the 11 tooth cog with a bigger chainring on the front as well.

    Your logic is that 12 teeth wears slower than 11 teeth just because there are more teeth to handle the forces from the chain at any given time?

    I only switch into my smallest cog when I'm taking off the wheel.

    @Kibbee But the bigger chainring scales up all of the cogs! Your 25 is now faster, too. A chainring swap cannot do exactly that what a switch from 12-25 to 11-25 does.

  • An 11-tooth cog is significantly less efficient than a 12-tooth one, even without the increased wind resistance at that speed.

    See the following in depth article "On the efficiency of bicycle chain drives"

  • One thing to ask yourself is "What is the max speed where I'm willing to expend energy, on a continuous basis, to maintain that speed?"

    Yes, it's (maybe) nifty to do 60 mph down a hill, but the energy required to maintain that speed on any sort of continuous basis is astronomical. Most people have a max sustainable speed (on the flat) somewhere between 15 and 25 mph (depending on the individual), and it makes no sense to have gears that permit you to pedal (at a semi-normal cadence) at a speed faster than your max sustainable speed. It's more valuable to have the "in-between" gears than high-speed gears you will never really use. At most you might want to "push" the high end ever so slightly to take advantage of that rare day when you have a nice tailwind.

    It's nifty to go 60 mph down a hill if its in front of a comparable climb, and you want as much momentum as possible to carry you up.

    @Michael - Any momentum you "stored up" on that downhill will be lost to wind resistance in the first 30 seconds of the climb. In terms of "conservation of energy" it's a very bad deal.

    Right, it really depends on the hill. For my commute, in one direction a certain hill is a 60 second climb on my best day, but going the other way with enough momentum I can clear the next lower hill and still be going 20-25mph at the top.

    Missing from this answer is the fact that it's usually counterproductive to even try pedaling down a hill where you can reach 60 mph/90 kph. On such really steep grades, if you want to maximize your descent speed it's better to forego pedaling and get into as aerodynamic a tuck as you can - even pulling your knees in tight and close to the frame is going to be beneficial at those speeds. See http://www.roadbikereview.com/reviews/study-reveals-most-aero-position-on-bike. You can try different values at http://bikecalculator.com/veloUS.html Try 400W/drops vs 0W/aerobars on a -10% grade.

  • Another way to see it is that while crosschaining is not that big of an issue with nowadays components (this has been confirmed to my on this very forum), the extreme cross-chainings are not very pleasant (noise, not completely smooth pedaling and so on,...). On the other hand, the second-to-last cog is very usable most on most (double) transmissions.

    Therefore, with a 11-25 cassette, you can ride on "small-ring"/12 rather than "small-ring"/13 like you can on a 12-25 cassette (regardless of whether the "small ring" is 34, 39 or anything else).

    In the same time, the 11 cog is not useless either as it can be used in downhills or sprints.

    On the other hand, if you are sure with your extreme gears usage, having the tightest possible cassette is better: I could rephrase your question and say: "why would one buy a 12-25 cassette when you can have a 12-21 which will allow faster speeds and has smaller gaps (actually almost none)?"

    The answer to that is actually the only right answer to your initial question and that is that your cassette must reflect what kind of rides you intend to use it for? loaded touring? flat racing? moutain racing?

  • 1

    Here is an excellent technical reason not to: maybe you simply can't put the 11-* cassette onto your hub.

    For instance, if we consider Shimano HyperGlide: the Shimano cassettes which have 11 cogs require the HyperGlide-C (compact) style hub, whose splines do not extend all the way to the edge. The 11 cog does not actually go onto the splines like the other cogs. It sits on the end of the hub, and partially goes onto the shortened splines. It requires a special variant of the lock-ring, which comes with the cassette. On the other hand, 12-* cassettes fit these compact hubs. For example, I'm using a 12-23 range CS-HG50-8 on a HyperGlide compact hub that previously had a 11. The shortened splines of the compact hub still adequately grab the 12 cog, so it doesn't rotate freely around the hub. (By the way, there you go: I'm a a live example of someone opting for 12, after using 11! I still just rarely use the 12).


    Related to point 1, the fact that a special hub is required tells you something: the 11 cog is technically inferior. It is on the specification fringes of what will possibly fit onto the hub, which is a bad place to be. It has to be constructed with partial splines, because if it had full splines to go onto a regular hub then the cog's hub would be too thin and weak. The splines not going all the way through the cog's inner hub allows there to be more steel to hold the entire part together. There is another way in which the 11 is inferior: you will commonly find, on even a lightly worn cassette, evidence that the chain plates are making contact with the 11T cog's hub! In other words, chains do not sit very well on the teeth of the 11; they ride the inner ring. If not when the cassette is new, then eventually. The 11 will likely be the first gear to start skipping when the chain and cassette wear. Since for many riders that's a big clue to throw out the entire cassette and chain, it may lead to unnecessarily frequent replacements.


    A cyclist that rarely uses a 12 will use an 11 even more rarely; perhaps never. Any gears you don't use effectively reduce the number of gears in your cassette. If you have a 9 speed cassette but only use 2-8, then you really have a 7 speed cassette, with spacing and padding cogs that make it compatible with your 9 speed shifter.


    Higher gear does not translate to faster. Your maximum speed over a short distance might not be achievable in the highest gear, in fact. One use for the highest gear is in fact to go slower, with a relaxed, slow cadence. A car analogy can be made here: it's like an over-drive gear that lets you work with lower RPM on the freeway, saving gas. (Car analogies are good, but they break down in one important way: car engines do not get tired, and do not have to pace themselves with regard to expected distance.) Just like a car, we can downshift on a bicycle to get more power. Yesterday, to catch a green light, I downshifted from 5 to 4 on my 12-23/8 cassette, accelerated, and outpaced the cars. Also, these downshifts have to be subtle: it helps to have the close gear ratios. To have close gear ratios, don't get a cassette which includes gears that you won't use! I was already pedaling at a decent cadence in 5; too much of an increase in cadence in the downshift would have been counterproductive: I would end up whipping my legs around, going nowhere.


    The 11 tooth cogs have a purpose: they go with compact drive systems which have a smaller ring in the front, like 48 teeth (or even less), common on mountain bikes. They are also useful for bikes with smaller diameter wheels. The 11 cog against a 48 ring gives you almost the same gear ratio as 12 against 52. The 11 cog is thus a useful accessory for converting a mountain bike for commuting use in an inexpensive way (avoiding replacing the front ring). Throw out the 13-34 cassette and put in an 11-25, slap on "road slicks" tires, and maybe some fenders and possibly a rack, and you're good to go. If this is what you're doing, the 11 may be for you.

    If you have a road bike with a 52 or 53 front ring, with 700c wheels and average sized pedal cranks, the 11 is probably a bad idea that you will regret, unless perhaps you're an elite cyclist with a "power plant" that works well with higher gearing.


    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.

    Actually, the desire for more teeth in the cassette is only understandable if the cyclist has no front derailleur. Or, say, only two rings in the front. Otherwise, the desire is, well, still understandable as a desire, but not all that rationally founded. If you have three rings, there is no need for anything larger than a 23 cog in the cassette. With the small ring engaged in the front and the 23 in the back, you have a ridiculously low gear that feels akin to riding a five-year-old's tricycle. If there is a section of road you can't climb with that, just get off and walk. The only cyclists who need anything lower are athletes who do mountain cycling as a sport, involving ridiculous feats like climbing very steep sections of a rough trail. (They must stay on the bike, because that's the sport; a "normal person" either wouldn't go there with a bike at all, or would just carry it up that section of trail).

    Bicycles marketed at the mass consumer market often come with ridiculously fat cassettes combined with three speeds in the front, which reinforces the consumer belief that these are good and necessary. It's not clear why this is, but it's probably for two or three reasons. It simplifies the use of the bike: the user can find every gear they need using the front derailleur only. Secondly, the number of speeds is often touted as a selling point to the general public. What happens when you put an 11-34 "Mega Range" cassette (say 9 speeds) into a mountain bike with three rings in the front is that the user ends up with effectively a 9 speed bike, with 18 additional gears that are either redundant or uselessly low. However it can be marketed in the flyer as a 27 speed bike. The large cassette also looks impressive, and consumers like words like "mega"; they think they are getting something special, or more for the money.

    "... only understandable if the cyclist has no front derailleur. Or, say, only two rings in the front." You say that as if having two chain rings is some sort of weird affliction that's relevant to almost nobody. Pretty much every road bike made has two chain rings.

    @DavidRicherby Thanks for the heads up; that is not very well worded there. There are some subtle issues as well. Road bikes sometimes have a second ring that is still a pretty high gear, like 52-42. Someone with a narrow-range cassette could struggle on hills with that 42.

  • The simple answer is that people (racers especially) like closely spaced gears so they pedal as closely as possible to their optimum cadence.

    And of course they know their optimum cadence down to three significant figures.

    It's not about knowing, but the feeling "I need to shift slightly up / down but next gear is too high / low"

  • Different strokes for different folks is all. Guys with arms like legs and legs like people have no need for a stump puller or even a 25 sometimes and are wishing for a 10 until they discover what a Campy set up costs while in my world of recreation and fitness a 12-28 seems almost perfect most of the time and I've even considered a 13 or even 14-27 from the 6600 junior cassettes. My first road bike was a '73 Fuji S10S 10 speed with a 14-17-20-24-28 and it seemed to be all I really needed (at the time) but now, at almost 70 yrs, bigger gears are my friend.

  • I hesitate to dig up an old question, but there is one answer missing.

    Maximum Gear ratio restrictions in Junior racing. That's why you'll also see 14-25 cassettes.

    USA Cycling rules on junior gearing

    It is almost impossible to get a crankset that meets the regs with an 11 tooth cog.( Generally max is 52/14 w/700c wheels and 23-25mm tires ). With an 11t, you have a most 40t in front and lower high gear. 12 isn't a lot better, but 44t is at least possible and is closer to 52/14.

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