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Gears - is broader better?

ansbaradigeidfranansbaradigeidfran Posts: 526
edited February 2009 in The workshop
Excluding professionals on TTs who need to keep a very constant cadence, I would have expected that a broad range of gears (e.g. 11-25 cassette) would be better than a narrower one (e.g. 12-23). Am I right in this? If so, why are wide and narrow ranges sold together like this?

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  • redddraggonredddraggon Posts: 10,862
    Some people want narrow ranges and some people want wider ranges. Some want a big big gear and small small gear, but other like smaller gaps between sprockets.

    What's the issue?
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  • No real confusion, just trying to understand the opinions of others, while doing some very early window shopping for my fixer-upper. I've got some slightly nasty hills around here, and appreciate my bouncy MTB's low gearing until I start spinning out on the level, so I'd want a wide range. I suppose narrow ranges would be more popular in less hilly areas. Correct?
  • Imagine your legs are an electric motor. Imagine that this motor is at it's most efficient rotating at 90rpm and puts out less power if it has to rotate at other speeds. At very low revs the motor will stall and not have enough torque to keep turning and at very high revs the motor will no longer be able to put out any meaningful power.

    The job of your gearing is to match the 90rpm output of this motor as efficiently as possible to the speed of the back wheel, which varies widely depending on incline, wind and so on. If your range of gearing is too wide then the gaps between your gears will be too wide and you'll spend most of your time at the wrong cadence. This will reduce your efficiency and lower your power output. If your range of gearing is too narrow, then most of the time you will have just the right gear but when you hit a big hill you won't be able to get up and you won't be able to apply any power on the way down.

    Choosing a set of ratios is a compromise between these two extremes. The best solution depends on the rider's goals and abilities. Racers and enthusiasts want to go as fast as possible and are usually very fit, so they will pick a high and narrow range of gearing. Unfit commuters are more bothered about comfort than speed and don't really have the power to make use of high ratios very often, so they go for a low and broad range. On a flat time trial, a racer will go for an 11-21 cassette to get the finest possible control, whereas on a mountain stage they need more range and will swap to an 11-25, picking their ratios to suit the course just like racing car mechanics would.
  • rb1956rb1956 Posts: 134
    I'm a commuter/shopper/general-pedalling-round cyclist, 50+ years old, and live in a hilly district, so I'm a member of the low-and-wide school of gearing. I run the Rohloff 14-speed hub, giving me 16-84 gear-inches (1.27-6.69m development). Naturally I spin out at about 40kph in my highest gear, but that only happens on downhill sections and then I just coast, so it works for me.
  • A triple 53/39/30 11-speed 12-26 (12,13,14,15,16,17,18,19,21,23,26) gives high/low/close.
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