And while you at it... some stuff to really get the brain cells cooking!
Effects of different size tires......
In order to get a true picture of gear ratio one must use tire circumference in the equation. If you run the same gears as someone else but you have 24" rear tire circumference and someone else has 22", the true ratios are not equal. To figure the true ratio you will want to use IPR (inches per revolution) which simply means the number of inches a buggy will travel per each revolution of engine.
To figure IPR use this equation: Rear Tire Circumference (x) time’s clutch gear (Y) divided by rear axle gear (z) = IPR. (X*Y)/Z =IPR. For example if one buggy (A) was running a 16t trans gear with a 39t rear axle sprocket gear and their tires were 24" the equation would be 24 x 16 / 39 = 9.84
9.84 is the IPR. This means the buggy would travel 9.84 inches per revolution of engine. If another buggy (B) had the same gears but had 22" tires, look what happens. 22 x 16 / 39 = 9.02. Approximately ¾ of an inch for every engine revolution. Don’t confuse engine revolutions with motor rpm’s. we are talking revolutions at the trans sprocket here! Even though both these buggy’s were using the same gears they were not running an equal set-up. Buggy [A] would be faster on the straights, Buggy [B] would be faster coming off the corners
. So what if buggy [B] wanted to run the same IPR as buggy [A] but still use the same tires? To figure that we can replace buggy B's 39 with buggy A's IPR. 24 x 16 / 9.84 = 39.024 This means that for things to be equal, buggy B would need to change their rear axle gear to a 40 or 41 .When the numbers fall into a fraction go to the next highest tooth count.
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