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  1. #1
    Traffic shark
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    A really stupid thread, it would seem.

    I'm the last man out of the cave.
    Last edited by SD Fixed; 03-22-07 at 11:15 PM.
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  2. #2
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    Because tires and wheels are different sizes so simple ratio doesn't provide as much information. Some would argue that gear inches don't provide enough information either.

  3. #3
    Senior Member pedex's Avatar
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    makes it easier to compare bikes with different sized wheels without having to do very much math

  4. #4
    nothing but a gnab gib
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    it's another way for people to be vague.

  5. #5
    Traffic shark
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    Quote Originally Posted by moe sizlack
    it's another way for people to be vague.

    right, I think you are.
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  6. #6
    Oh god it hurts!
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    why do thermometers have numbers on them?

  7. #7
    current member
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    How else to make a schematic comparison of ,say 44x17 and 50x19. Which is bigger? How would you measure if not in distance travelled?

  8. #8
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    Quote Originally Posted by cphfxt
    How else to make a schematic comparison of ,say 44x17 and 50x19. Which is bigger? How would you measure if not in distance travelled?

    well if the wheel size is the same it's easy
    2.58 vs 2.63

  9. #9
    domestique squeakywheel's Avatar
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    Quote Originally Posted by William Karsten
    Perhaps I'm getting old an onerous, like 165.

    But really, why do gear inches matter to people? I can't for the life of me understand why it @#$@# matters. It seems people obsess over it. I started 42x16. It got easy. I bumped up once to 44x16. Things weren't hard. I built some stamina, some speed, got comfy and went 48x15. Which seems plenty. How would gear inches play into this? It seems to me that it really superflous information.

    Or, I'm the last man out of the cave.
    Other people obsess over it? Seems you're the one changing your gearing all the time.

  10. #10
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    Its a way of expressing how easy or hard a gear is. Since there are many equivalent gears, for example a 51/17 is exactly the same as a 48/16, its easier to talk about gear inches, which is the number of inches the bike travels with one revolution of the pedals, than it is to talk about specific CR/cog combinations.

    In general, a 70 inch gear is a pretty easy around town gear for the flats. The 42/16 gear you started with is about 70 inches. Track racers usually ride something in the 88-92 inch range. Your 48/15 is about 86 inches, so you are getting up there with the track racers.

    Easy to calculate, Cr teeth divided by cog teeth times 27 gives you gear inches.
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  11. #11
    lunatic fringe Dogbait's Avatar
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    Quote Originally Posted by moe sizlack
    it's another way for people to be vague.
    There's nothing vague about a system that measures exactly how far down the road your particular set-up will carry your butt for each turn of the crank.

  12. #12
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    Quote Originally Posted by William Karsten
    I started 42x16. It got easy. I bumped up once to 44x16. Things weren't hard. I built some stamina, some speed, got comfy and went 48x15.
    All this means nothing without tyre/wheel size factored in. hence gear inches.

    and some will say that gear inches is useless without taking crank length into account. hence sheldon's gain ratios.

  13. #13
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    Quote Originally Posted by Dogbait
    There's nothing vague about a system that measures exactly how far down the road your particular set-up will carry your butt for each turn of the crank.
    you=wrong.

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    Quote Originally Posted by Dogbait
    There's nothing vague about a system that measures exactly how far down the road your particular set-up will carry your butt for each turn of the crank.
    That's not exactly how gear inches work and it is still vague compared to gain.

  15. #15
    Senior Member pedex's Avatar
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    except gear inches doesnt equal distance traveled per crank revolution

    circumference= Pi * diameter

    gear inches = gear ratio * wheel diameter

    actual distance traveled per crank revolution is gear ratio times circumference

  16. #16
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    a 72 inche gear is equivalent to riding a highweel bike with a 72" front wheel.

  17. #17
    blah onetwentyeight's Avatar
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  18. #18
    nothing but a gnab gib
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    Quote Originally Posted by Dogbait
    There's nothing vague about a system that measures exactly how far down the road your particular set-up will carry your butt for each turn of the crank.
    oh sorry, was i being vague?

  19. #19
    jack of one or two trades Aeroplane's Avatar
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    Quote Originally Posted by William Karsten
    But really, why do gear inches matter to people?
    One valid reason I can think of is going between offroad 26" and 29" wheeled bikes. In order to keep your gearing consistent, you figure out the gear inches and keep that the same.

    I agree with you for on-road stuff though, not many folks go between 650c, 650B, and 700c at all.
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  20. #20
    Run What 'Ya Brung bonechilling's Avatar
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    Quote Originally Posted by moe sizlack
    it's another way for people to be vague.
    Totally OT, but you know that you spelled "Szyslak" wrong,
    right?

  21. #21
    Perineal Pressurized dobber's Avatar
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    Quote Originally Posted by bonechilling
    Totally OT, but you know that you spelled "Szyslak" wrong,
    right?
    You're both wrong



    Sleestaks
    This is Africa, 1943. War spits out its violence overhead and the sandy graveyard swallows it up. Her name is King Nine, B-25, medium bomber, Twelfth Air Force. On a hot, still morning she took off from Tunisia to bomb the southern tip of Italy. An errant piece of flak tore a hole in a wing tank and, like a wounded bird, this is where she landed, not to return on this day, or any other day.

  22. #22
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    Quote Originally Posted by Aeroplane
    One valid reason I can think of is going between offroad 26" and 29" wheeled bikes. In order to keep your gearing consistent, you figure out the gear inches and keep that the same.

    I agree with you for on-road stuff though, not many folks go between 650c, 650B, and 700c at all.
    But people do go between different tires often enough. When it snows I put a 32C xcross tire on my rear wheel, which increases the gear inches of my bike.

  23. #23
    hello roadfix's Avatar
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    I need at least 80 inches to stay with my Sat morning geared group ride.
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  24. #24
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    Quote Originally Posted by San Rensho
    Since there are many equivalent gears, for example a 51/17 is exactly the same as a 48/16,
    while we're on the topic:

    can someone sum up the advantage/disadvantage (if any) of 2 different combinations that have the same gear inches?

  25. #25
    hateful little monkey jim-bob's Avatar
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    Quote Originally Posted by Aeroplane
    I agree with you for on-road stuff though, not many folks go between 650c, 650B, and 700c at all.
    Ahem.

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