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Thread: Cog sizes

  1. #1
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    Cog sizes

    I have an 8sp cassette on my bike right now. What advantage(s), if any, would there be to switching over to a 9sp (other than being able to find better shifters)?

    Also, in general, how does one decide what's best between the different choices of cogs available? How do I know to pick 11-21, or 12-23, or whatever? I don't need exact science here (unless someone wants to offer it), just some general knowledge to help me decide which one might work best. AND, I'm considering ditching my big front chainring for a bash guard since I never use it. My other 2 chainrings are 22 and 32T. What is the advantage of changing the 32T chainring to a 34 or 36T chainring? What combination of rear cassette and front chainring(s) works best for most of you?

  2. #2
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    Keep the 32 Chain ring and get a 9 speed 11-32 or 11-34 in the back. Then you will need the new shifters, and possibly a new derailluer if it cant cant a 9 speed.

  3. #3
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    There's not a really a compelling reason to upgrade to 9sp imo. Gear spacing will be marginally tighter with 9sp, and you might get a lower gear (34t vs 32t depending on your current cassette). Spares/replacement parts will be easier to find for 9sp. If you're content with what you have now, I wouldn't think 9sp would make much sense.

    If you decide to go 9sp, you're probably better off going 11-34, for the wider gearing spread. 11-32 is also another popular choice if you don't need the 34t low gear. If you don't use the big ring, by all means get rid of it. It'll provide you with greater ground clearance and you won't have to worry about your pant legs or shins getting chewed up any more. Personally I stayed with the 22-32, seems like a good setup to me. If you are a stronger rider and/or like to pedal the downhill sections you might think about the 34t or 36t.

  4. #4
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    You have to base any gearing decisions on your personal needs. The best indicator of what you want is the gears that you are or are not using now.

    Using a narrower cassette has the benefit of a better selection of closer spaced gear choices in the mid range, though at the expense of a possibly inadequately low bottom gear.

    Likewise with your choice of chainring. Dumping the outer may mean you'll want something bigger up front to give you a higher upper end, though if you've been happy with the 32t, why change it and lose some low end range?

    My advice is to make note of the gear combinations you're currently using (and not using), then use the gear calculator here to figure which combination of chainrings and cassette will give you the most usable gears on your proposed 2x9 setup.

    http://www.sheldonbrown.com/gears/
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    www.chain-L.com

    The key to solving any problem is to understand and address the underlying cause.

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