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11-09-04, 12:23 PM
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.