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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 03-21-07, 01:55 PM   #1
SD Fixed
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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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Old 03-21-07, 01:58 PM   #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.
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Old 03-21-07, 02:00 PM   #3
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makes it easier to compare bikes with different sized wheels without having to do very much math
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Old 03-21-07, 02:02 PM   #4
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it's another way for people to be vague.
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Old 03-21-07, 02:03 PM   #5
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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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Old 03-21-07, 02:26 PM   #6
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why do thermometers have numbers on them?
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Old 03-21-07, 02:42 PM   #7
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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?
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Old 03-21-07, 02:44 PM   #8
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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
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Old 03-21-07, 02:45 PM   #9
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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.
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Old 03-21-07, 02:46 PM   #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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Old 03-21-07, 02:46 PM   #11
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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.
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Old 03-21-07, 02:49 PM   #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.
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Old 03-21-07, 02:49 PM   #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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Old 03-21-07, 02:49 PM   #14
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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.
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Old 03-21-07, 02:50 PM   #15
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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
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Old 03-21-07, 02:52 PM   #16
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a 72 inche gear is equivalent to riding a highweel bike with a 72" front wheel.
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Old 03-21-07, 02:54 PM   #17
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read this: http://www.sheldonbrown.com/gain.html
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Old 03-21-07, 02:54 PM   #18
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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?
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Old 03-21-07, 03:06 PM   #19
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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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Old 03-21-07, 03:15 PM   #20
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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?
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Old 03-21-07, 03:53 PM   #21
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Totally OT, but you know that you spelled "Szyslak" wrong,
right?
You're both wrong



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Old 03-21-07, 04:02 PM   #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.
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Old 03-21-07, 04:10 PM   #23
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I need at least 80 inches to stay with my Sat morning geared group ride.
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Old 03-21-07, 04:18 PM   #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?
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Old 03-21-07, 04:47 PM   #25
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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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