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  1. #1
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    Is 43/18 the same as 32/14 ?

    Anyway while doing some urban riding my friend some smoked me on his bike. His gearing is 42/20 while mine is 32/18.

    I was told by the bike shop that if I changed my ratio to 32/14 I would be able to achieve parity. Although the ratio numbers are comparable is changing out my 18t cassette to a 13t cassette going to give me the same performance as someone on a 42/20 ?

  2. #2
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    A calculator will give you all the information you want on ratios : http://www.sheldonbrown.com/gears/

  3. #3
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    32/18 = 1.78:1 = 12.3mph @ 90rpm
    42/20 = 2.10:1 = 14.6mph @ 90rpm

    43/18 = 2.34:1 = 16.6mph @ 90rpm
    32/14 = 2.43:1 = 15.9mph @ 90rpm
    32/13 = 2.46:1 = 17.1mph @ 90rpm

    As you can see, you are running the lowest gearing of the bunch currently. The 42/20 isn't that much higher. 34/14 is pretty significantly higher. In the end, it all depends how much gear you can push, and how fast you can spin. For urban riding on a mtb with slicks, I would probably gear in the neighborhood of 2.4:1. (38:18, 32:14). With knobbies, probably a little lower.

  4. #4
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    Just divide the chainring tooth count by the cog tooth count for whatever different combinations you have, and see how they compare. That gives you the gear ratio (assuming same tire diameter). A higher gear ratio will give you a higher top speed, but require more torque to accelerate or on hills.

  5. #5
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    Thanks alot guys! Of course that begs the question, why did this guy chose a 42/20 setup and change his front ring from 32 to 42 when he could have simply changed his rear cassette to 14/15 and achieved the same results?

  6. #6
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    Lots of reasons. Maybe he has a 20t that is really nice, and doesn't want to not use it. Could be that he had easy access to a 42t chainring but not a 14 tooth cog.

    Also, there are certain advantages to running higher tooth counts like increased chain engagement and a smoother drivetrain. Everything tends to last a little longer also.

  7. #7
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    Quote Originally Posted by sunset1123
    Also, there are certain advantages to running higher tooth counts like increased chain engagement and a smoother drivetrain. Everything tends to last a little longer also.
    Yeah, I noticed a bit of this even with a larger chainring/smaller cog combo (the 36x16 half of my dinglespeed). The larger ring was apparently enough to add some smoothness. I am strongly considering switching my main SS ratios to be based around the 36t ring, such as 36x22 instead of 32x20, but the main drawback for me would be buying more expensive cogs instead of the $3 stamped cogs

  8. #8
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    Quote Originally Posted by boomn
    Yeah, I noticed a bit of this even with a larger chainring/smaller cog combo (the 36x16 half of my dinglespeed). The larger ring was apparently enough to add some smoothness. I am strongly considering switching my main SS ratios to be based around the 36t ring, such as 36x22 instead of 32x20, but the main drawback for me would be buying more expensive cogs instead of the $3 stamped cogs
    Yeah... it does cost a little more... but I was running 38/22 for a bit and it was probably the smoothest drivetrain I have ever ridden. Surly SS 22T is really really nice, and lasts forever. Another drawback may be that this makes the chain really long. When I went to go get a new chain, the one I wanted wasn't long enough. Ah well.

  9. #9
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    I just did a ride last night with 36x20, the lowest gear I could make with what I already had but still higher than I had been riding. It definitely felt good! Hmm, it is my birthday tomorrow

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