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| *Vultures Knob>>>Bike Pedals |
How would you go about figuring out a gear ratio?? |
I mean, yes, if it were a circle, all i'd have to do is find the circumfrence of the back gear, (on a bike) and divide the bigger front gear's circumfrence by that. but the thing is, the number of teeth vary from one set to another, and i want to make sure i'm putting my money in a new set of gears with a good enough difference. Also, some gear sets have slightly elliptical gears to make pedaling easier, (mine are too, but very very slightly.) i'll need to know how to figure in the number of teeth and the tooth size if possible. thanks! Hi Adeel, Don't get too involved, my friend. It's simplicity itself: no. of teeth on the chainwheel divided by no. of teeth on the sprocket times the diameter of the wheel in inches, and that's it. For example, if you have a 48-tooth chainwheel, a 16-tooth cog and a 27" wheel, it's 48 divided by 16 times 27 = a gear of 81 inches. Sure tables are handy, but why bother? It's a little more difficult if you have "hard" numbers like 17, but, never mind, that gives you something to think about on a long ride. You will still need to count the chainring teeth (front gear) and the sprocket / cassette (rear gears) teeth. John Forrester explains the basic formula is gear = (wheel diameter times chainwheel teeth) divided by rear sprocket teeth. The result will be the inch equivalent of an "ordinary"- remember those huge front wheel bicycles? The taller and stronger you were, the bigger the front wheel. The above formula will show you the gear equivalent. The metric version: "development" (distance traveled by one pedal revolution) = (wheel circumference times chainwheel teeth) divided by rear sprocket teeth. Sheldon Brown has an online calculator: http://www.sheldonbrown.com/gears/... That offers some drop down with stock cassette, and offers a number of outputs, including development, inches, and gear ratios. You will still have to count the teeth for each chainring (chainwheel / front gear). It's easier to count the teeth if you have a bike stand, and starting near the crank will likely be easiest if you get lost counting. Effective Cycling, 6th ed. John Forrester dude just use Sheldon's gear calculator and save yourself the headache. God Bless Sheldon Brown. and buy something from him to pay him back, this ain't no charity he's runnin. You count the teeth my man and devide like you said. eliptical is out. Biopace as Shimano called it. No one uses it, but it goes around so use it if ya got it. Most are from the early '90s. Finally, all the work's been done for you, pal. There are a few very standard set ups. They are standard because all the ratios have been worked out for decades. You don't say if you talking road or MTB. I'll assume road for this example: Standard double chain rings: 53x39, compact is 50x30 I think. Standard 9 speed cassette (others are similar): 11 to 23 12 to 23 12 to 25 12 to 27 I ride road and ride hard. My terrain is somewhat flat to rolling hills for the most part. A few steep hills here and there. I, like many performace riders use 53x39 and 12-23 (some use 12-25, some 12-21) If fact if you buy a cassette you can't customize your cogs really. Most are on carriers and can't be changed. |
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