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Thread: Bike Gears

  1. #1
    mtbr member
    Join Date
    Apr 2013

    Wink Bike Gears


    I've always biked but I recently decided to take it to the next level. I recently got a great new bike (21 speeds - 3 & 7) but I never understood how changing gears work. I am not really looking for long explanations (counting gear teeth or how the smaller front ring is for climbing - that is obvious...etc).

    If you can, along with your explanation, please answer this because this example will give me a better understanding. If I am in front ring 2 and back ring 6, which gear am I really in?

    Thanks so much.

  2. #2
    mtbr member
    Reputation: MSU Alum's Avatar
    Join Date
    Aug 2009
    It always comes down to Sheldon: Sheldon Brown's Bicycle Gear Calculator As to what gear you're in, 2 & 6. When I'm riding with someone new and they ask, I say 2 up front (on the left) 6 on the back (on the right). That's only to get them acquainted with gearing. There are other gear combos that are close. The bottom line is, use whatever it takes. Going back to the "olden days" when I was learning to land on a carrier, the first question I asked the instructor was, "what power setting do you use". His answer was the answer to most of life's questions..."Whatever it takes!"

  3. #3
    Join Date
    Jan 2004
    First, just forget about the "21 speeds" part. It does not work like that.

    Think of each front gear (chainrings, or "rings") as a general gearing "range". Once in a given ring, the rear gears (collectively called the "cassette" and each individual gear is a "cog") let you move within that range.

    When people talk about what gear you are in, they usually refer to the rear cog by number, and the front by ring size. Saying "2nd gear" by itself does not mean much because you don't know whether that means second gear in the small, middle, or big ring. You would say something like "2nd gear, middle ring", or maybe "middle / 2nd". Saying "12th gear" is meaningless. If you want to be really precise, you might give the actual tooth counts. "I was in 32 / 13" means that you were in the 32t ring (most likely the middle ring on a triple chairing set up) and the 13t cog.

    The reason that it is not useful to think about this as a 21 Speed is because the range you get from the three rings overlap with each other. In most cases, once you get up to the 2nd or third cog in one ring, it is about the same as being in first gear of the next biggest ring. In other words, many of those 21 gear combinations are redundant. This is why people on sites like this would refer to your setup as "3x7" rather than "21 Speed". You might even hear you bike referred to as "7 Speed" in reference just to the rear. When you see discussions here about 9 speed vs 10 speed, they are referring to the rear.

    When selecting which combo to use, the main thing you want to keep in mind is not too cross-chain too much. In other words, when you are in the small ring, try to stay away from the smallest cogs, and when in the big ring, stay away from the largest cogs.

    Since the ranges of the 3 rings overlap, this means you often have the option of using one of two rings to get a certain gear ratio. (for example, small/5th might be the same gear ratio as middle/2nd) I think that as a general rule, it is better to be in combo using the larger chainring (unless that is going to entail cross-chaining). Being in a larger chainring and cog means less chain slack flopping around, and less likely to drop a chain, especially when going over rough terrain.

    People have different ways to think about using the various combos. For me, I tend to stay in the middle ring most of the time. I only drop to the small ring to use the 2 or three lowest gears there. On bikes where I have a big ring, I just go up to that when I know I will be there for a while, like if I am going downhill.
    15mm is a second-best solution to a problem that was already solved.

  4. #4
    Professional Crastinator
    Reputation: Fleas's Avatar
    Join Date
    Jan 2006
    ^^^ Super-excellent answer!

    It's never easier - you just go faster.

  5. #5
    mtbr member
    Reputation: JoePAz's Avatar
    Join Date
    May 2012
    on a triple.

    Small ring = for steep climbs or really slow speeds.
    Middle ring = flats, shallow short climbs, and most descents
    Big ring = fast pavement spins or some fast descents.

    In rear you use what ever gear you need to get comfortable cadence. Also try to avoid cross chaining. This is using the small ring front and smallest cogs in the back. The chain gets pulled at bad angles and is not good. Plus you don't need to do this as you have overlap so that ratio is probably the same with middle ring and larger cog. Same goes for big ring and big cog. You can use middle ring all the rear cogs, but in small ring stay out of the smallest 2 or 3 cogs and on the big ring stay out of the largest 2-3.

    Also don't shift under max power as it is hard on the parts. Back off the power a little to allow the derailers to work. So best to shift into the right gears before you need them. Doing this takes practice to know what gears you need.
    '18 Specialized Epic 29", Vassago Verhauen SS 29", '13 Santa Cruz Solo 27.5", XC, AM, blah blah blah.. I just ride.

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