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Thread: 24 vs 27 speed?

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    Please use a descriptive title

    Can someone explain what is better; 24 vs. 27 speed or the size of the crankset.

    Or is more and bigger always better?

    ed

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    A Heart Needs a Home Rich Clark's Avatar
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    It's not so much that 9-speed drivtrains are that much better than 8-speed. It's that if you're buying new gear, the state of the market is such that 8-speed drivetrains indicate lower-end groups; all the better stuff is now 9-speed or (for Campagnolo road groups) 10.

    On a used bike, of course, you might very easily find some older 8-speed parts that are top of the line, and if they were unworn might still be preferable to new entry-level 9-speed parts.

    If I ran across a pristine used bike with a Campy Record 8-speed drivetrain, would I choose it over a brand-new bike with Shimano Tiagra? You betcha.

    So if everything else is equal, that extra cog can come in useful, whether it's used to get tighter spacing on a roadbike or more range on a touring or MTB. But the quality of the group has to be considered as well, and the bike it's mounted on. In new bikes today, you won't find 8-speed drivetrains on anything but entry-level models.

    RichC

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    Im not wearing any pants! adaze's Avatar
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    depends what you want to do wif the bike and how fit you are i guess, 27 gives you a bit of an easier time up hills, and really just an extra few gears that give you a bit of extra choice when climbing. 9 speeds are standard so go wif that is my advice, unless your getting a second hander. Just becasue it comes wif only 8 speed doesnt make it suck, dont over look a great bike that is a few years old just for a few extra gears, but if your buying new definatley 27
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    Ive ridden bikes with 1,3,5,10,12,21, and 24 gears.
    In my experience, in very hilly terrain, you dont really notice the extra cogs beyond 21 gears for everyday utility riding. The most important factor is the lowest gear you have. Most bikes come with plenty of duplicate gears, and plenty of gears too high to be of much use.
    9 speed is just a marketing gimmick, which you pay for with cogs and chains that are too thin, and cog spacing so close that the gears need finer adjustment.
    You also need wheels built with too much dishing to make space for all the cogs.

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    Just ride. roadbuzz's Avatar
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    Originally posted by MichaelW
    Ive ridden bikes with 1,3,5,10,12,21, and 24 gears.
    What! No 16 or 18!?!?

    Ed, I don't understand your comment about size of the crankset, with respect to 24 vs. 27. I agree more or less with what Rich is saying. Either will give you an ample range of gears, so I'd look at the whole set of associated components with each and see what you're getting... shifters, derailleur, etc., etc., and where it puts you in terms of what you're looking for in terms of quality, maintainability, upgrade path, etc.

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    Senior Member mike's Avatar
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    I might get chewed on for this, but anything more than 18 gears is a waste and a compromise.

    I believe that all you really need is three chainrings in the front and six sprockets in the back. Everything else is marketing gimmickery. Even with 18 gears, you will have a lot of duplication of ratios. The main thing is to have the smaller chainring to go up steeper hills (especially if touring with a heavy load). For many (not all - I didn't say all...) riders, I question the need for the large chainring except for trying to exceed 40 mph going down a hill.

    In order to accomodate more than six sprockets (8,9,10) on the freewheel, sprockets were made thinner which causes them to wear and break easier.

    Additionally, the chains had to be made thinner to accomodate the thinner sprockets.

    Of course, you'll have a dandy time trying to find components for an 18 speed rig these days.
    Mike

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    Originally posted by roadbuzz

    What! No 16 or 18!?!?

    Ed, I don't understand your comment about size of the crankset, with respect to 24 vs. 27.
    I confused things a little when I stated my question, sorry about that.

    Question 1 refers to the number of gears and I thank all that answered that part of the question your input has been very helpful.

    Question 2, which wasn't so clear refers to the different sizes I see for cranksets (or chainwheel?), some have numbers like 52/42/30 compared to 42/34/24.

    I guess I'm asking if you have more gears and a smaller crankset is that any better or worse than having less gears and a larger crankset? Or should you always try to get the most gears and the largest cranksets?

    ed

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    Devilmaycare Cycling Fool Allister's Avatar
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    Originally posted by mike
    I might get chewed on for this, but anything more than 18 gears is a waste and a compromise.
    Why would I chew on you for that? You know it's true.
    If we learn from our mistakes, I must be a goddamn genius.

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    Senior Member (Retired) gmason's Avatar
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    Everything so far sounds right to me. But...

    Isn't it best to have the widest possible range of gears for both speed on the flat and climbing ability (given appropriate terrain, unlike here in North Holland )? And if so, won't the commercially available gearsets offer that only with the largest set of combinations, achievable with a 3x10 setup (though I would leave ten speed out simply because of cost)?

    There could be more duplications, but possibly a broader range with smaller increments as well.

    I think a pencil and paper have made their need felt.

    Cheers...Gary

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    Originally posted by ed gavin


    Question 2, which wasn't so clear refers to the different sizes I see for cranksets (or chainwheel?), some have numbers like 52/42/30 compared to 42/34/24.

    ed, the numbers you see refer to the number of teeth on each of the chainring cogs, ie 52 on the outer, 42 on the middle and 30 on the inner.

    compact chainsets are usually a few teeth less than the standard drive. compact is the industry standard for a new bike and standard is older. really you wouldnt notice much difference to be honest. the compact drive does is save weight and give better ground clearance, whilst keeping the same gear ratios as the standard drive. i have just bought new cranks and chainrings and went for the compact, but it isnt really a life changing decision, you should be happy either way as long as you get good quality rings.

    other sizes that come on cranks refer to the length of the crank arm i.e. 170mm, 175mm, 180mm. this is just really personal preference, i think 175 is the most standard of the sizes, but dont quote me on that, i think it changes from manufacturer to manufacturer.
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    Originally posted by ed gavin
    I guess I'm asking if you have more gears and a smaller crankset is that any better or worse than having less gears and a larger crankset? Or should you always try to get the most gears and the largest cranksets?
    Crankset size is a complete separate issue from gearing, and has more to do with bike fit.

    If you search the site, there has been some good discussion on this before. Here's a general reference for bike fit. I wish I could provide a better reference, as they muddle their crank length description with a lot of subjective stuff that is really only useful for fairly experienced cyclists. But crank length is an inexact science. The best starting point, IMO, is leg length. Unfortunately, I don't remember the numbers, and can't find a web ref with specifics to point you to. So, I'll tell you what works for me, and hopefully someone else will jump in and provide better specifics. My trouser inseam length (don't recall my floor-to-crotch measurement) is 31", and I ride a 55cm (measured c-t) frame. 170s or 172.5s will work for me, but I'm more of a masher than a spinner, so I use 172.5s. In general, though, if you're borderline and not sure, it's better to go with shorter cranks, which tend to put less stress on the knees.
    Last edited by roadbuzz; 05-20-02 at 06:00 AM.

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    A Heart Needs a Home Rich Clark's Avatar
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    Originally posted by ed gavin

    Question 2, which wasn't so clear refers to the different sizes I see for cranksets (or chainwheel?), some have numbers like 52/42/30 compared to 42/34/24.

    I guess I'm asking if you have more gears and a smaller crankset is that any better or worse than having less gears and a larger crankset? Or should you always try to get the most gears and the largest cranksets?
    The right gearing is that which best matches the specific rider to the type of riding s/he's doing.

    Keep in mind that you should avoid cross-chaining (using an inside chainring with an outside cog, or vice-versa). Therefore you can see that by basic design, the biggest chainrings are intended to combine mostly with the smaller cogs, and vice-versa.

    Using the calculator at http://www.sheldonbrown.com/gears/ you can see that on a bike with a 52-42-30 crankset and an 12-25 cassette, a pedaling cadence of 80 would give you a speed range of 7.5 to 27.1 mph. Appropriate for a road bike. Less appropriate for a touring bike. Not at all appropriate for a mountain bike.

    Do the same calculation with a 42-32-22 and a 12-34 cassette, and you get a speed range of 4 - 21.6mph. This bike would be able to climb almost anything, although it would spin out on the road for many riders.

    IMO, most road and touring bikes today are geared too high; only road racers and those who ride like one need or can really use a 52-11, whereas almost everyone sometimes wishes for lower gears than what they have.

    Many of today's hybrids come with what I feel is close to perfect gearing for a multi-purpose 700c bike: 48-36-28 in front, 11-32 in back. 12-34 would be even better.

    RichC

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    First, compute the ratio between the highest gear you can spin without terrifyng yourself with excessive speed and the lowest gear you need to conquer any reasonable grade. On my mountain bike, this happens to be exactly 4:1 (48/13 to 24/26). Since I like having my gear ratios spaced about 6 to 7 percent apart, with possibly bigger gaps at the bottom and the top, and with crosschain combinations excluded, I can barely cover this range with 21 well-contrived gears, which I do with 48-40-24 / 13-15-17-19-22-24-26. Twenty-four gears would be better (13-14-15-17,... would eliminate the gap at the top), and 27 would allow for a few redundant ratios.

    On the road bikes, I happily use an 18-speed half-step-plus-grannie (48-45-34 / 13-15-17-19-21-24) or a 14-speed 1.5-step (50-42 / 13-15-17-19-21-23-26 or 52-44 / 14-16-18-20-22-24-28). On the latter setup, going from 14 to 16 speeds would allow me to close the gap on top.

    My personal conclusion is that I would like to have 16 or 18 speeds for a road bike, but can live with 14; I would like to have 24 or 27 speeds for a mountain or loaded tourng bike, but can live with 21.
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    You can calculate the "size " of the gear in gear inches:
    (no of teeth in chainwheel/teeth in cog)X wheel diameter in inches.
    This way you can compare gears even with standard and compact chainrings, and determine the overlap between 2 rings.

    I find that 28" to 100" range covers me for steep terrain on roads with shopping loads, but could always use a lowe gear.

    Crank size should be determined according to ergonomics (related to the size of your legs, somehow), but it does feed into the gear ratios.
    If you are riding a single speed, and change from 170mm to 150mm, you will find it harder to pedal. If you change to 190mm, it will be easier to pedal. You have just "changed gear".

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    Pat
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    Cranksets can make a difference. The 52/42/30 is usually what comes with Shimano 105 and Ultegra. I think these are compatable with a rear cog of no more than 25. I think you can put a longer derailler on and then get a rear cog of 28 or 30. A 30/25 is a pretty low gear but if you want to climb long very steep hills, it might not be enough - for that I prefer a 1 to 1. By long and steep, I a long mountain pass with sustained grades of 7% or more. I found that a 1:1 was just about right on Teton Pass (sustained grades of 10%). I find a 39/25 is just fine for a 7% grade that is less than a mile long.

    Your own gearing preference and riding style are important. I like spinning up long hills and many people just slow their cadence down. With my fairly high spin, I am usually in a lower gear than most riders and I virtually never need anything higher than 53/13 and usually I don't need that.

    A 52/42/30 will give you the big gears, but maybe not the small gears. I would be a bit leery of using it for loaded touring.

    A 46/36/26 will give you the low gears, but then you might not have the high gears.

    You get a trade off on this stuff. If you have a wide range which gives you the high gear you need for high speed and the low gear for climbing, then you probably end up with fairly large jumps between gears. If you are doing riding at high speed in pacelines, it is nice having gears that are close together because that way you can be in the right gear at most speeds. Of course, if your gears are close together than you don't have the range and probably have sacrificed the low gears for hill climbing.

    There are a couple of solutions. One solution is to have 2 rear clusters. One for "fast" rides with tight gearing and one with a wide range for "hilly" riders. The other solution is to have 2 bikes.

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