Interesting gearing fact-type thingy
11-09-04, 01:23 PM
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Interesting gearing fact-type thingy
I read a letter in this month's Cycling Plus about an apparently simple way to select the correct gear for your ride. Basically, you want a gear that you can spin at about 95 rpm at your desired speed. So if you want to ride at 17mph, you (in theory) want about 61 inches (48/21). The guy that wrote the letter didn't provide the maths, so I grudgingly obliged 
To find your perfect gear ratio, take your preffered speed, in miles per hour, and mulitply by 0.134.
To find your perfect gear inch number, multiply that number by 26.6.
So if you want to ride at 15mph, do 15 x 0.134 = 2.01 (that's your ratio). 2.01 x 26.6 = 53.466 (that's your inches). So you'd need something like 46/23 or 39/19.
Obviously you may not like spinning at 95rpm, but if you know your ideal cadence the formula would still work with a bit of recalculating.
*These figures are based on 700c wheels; if you want the numbers for any other size, measure the diameter of your rear wheel (try to be accurate) and post it here, I'll work it out for you.
To find your perfect gear ratio, take your preffered speed, in miles per hour, and mulitply by 0.134.
To find your perfect gear inch number, multiply that number by 26.6.
So if you want to ride at 15mph, do 15 x 0.134 = 2.01 (that's your ratio). 2.01 x 26.6 = 53.466 (that's your inches). So you'd need something like 46/23 or 39/19.
Obviously you may not like spinning at 95rpm, but if you know your ideal cadence the formula would still work with a bit of recalculating.
*These figures are based on 700c wheels; if you want the numbers for any other size, measure the diameter of your rear wheel (try to be accurate) and post it here, I'll work it out for you.
11-09-04, 01:30 PM
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Sweet. So to travel at my ideal speed of 57mph, I'd need to run 101/13. Anybody know somewhere I could order that so I'd have it tomorrow? Or maybe I could do 55/7. That way I know it'd fit in the frame.
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11-09-04, 01:34 PM
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Doesn't the tire size affect the actural diameter? sortof like wheel diameter + 2 x tire diameter = rolling diameter.
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11-09-04, 01:55 PM
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11-09-04, 01:56 PM
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My calculation did not work, i got an error!
0.134. x fasssssst = error
....maybe if i try just 1 "s" in fast.....
0.134. x fasssssst = error
....maybe if i try just 1 "s" in fast.....
11-09-04, 01:58 PM
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Originally Posted by ostro
My calculation did not work, i got an error!
0.134. x fasssssst = error
....maybe if i try just 1 "s" in fast.....
0.134. x fasssssst = error
....maybe if i try just 1 "s" in fast.....
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