Gear (Photo: @rusdock1 via Twenty20)

How to Calculate Gear Ratio

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Gear (Photo: @rusdock1 via Twenty20)
When it comes to your car, calculating any kind of ratio can be daunting; however, calculating your gear ratio might be easier than you think. If you’re still stumped after trying to work through the formula below, your local mechanic will easily be able to calculate the ratio for you during your next routine maintenance appointment.
Gears may not make the world spin round, but they make a lot of other things spin — including, bike wheels, watches, and even certain kitchen utensils.
A gear is two (or more) toothed wheels coupled together to control the speed of rotation (RPM) of a motor drive shaft. The extent to which a gear system can modify rotational speed depends on the sizes of the tooth gears and it’s called the gear ratio.
The formula to calculate gear ratio is relatively straightforward: count the number of teeth on the output gear (or the driven wheel) and divide that by the number of teeth on the input gear (or the driver wheel), which is the gear connected to the motor.
A higher gear ratio will allow your car to accelerate better. Are you interested in determining the gear ratio on your car? If so, follow these steps.

How to calculate gear ratio

To calculate gear ratio, you need to know the number of teeth on your first and second gears. The formula for calculating gear ratio is Gear Ratio = T2/T1 (Gear 2 teeth/Gear 1 teeth). The rotational speed of interlocking gears determines how quickly they will turn.
The first gear is the drive gear and can be found attached to the motor shaft. The second gear is the driven gear and is attached to the load shaft. There might be other gears in between the two that will also factor into the calculation.
As an example, imagine the drive gear (T1) has 10 teeth and the driven gear (T2) has 20 teeth. Divide 20 by 10 or 20/10, which equals 2/1 or 2. This means that the driver gear (smaller of the two) must turn 2 times to make the driven gear turn once.
If there are other gears involved, then it is called a gear train. The additional gears are referred to as “idler gears.” The only difference, in this case, is you have to determine which of the gears is the drive gear and which one is the driven gear. Then you calculate the ratio using the same method above (as if there were only two interlocking gears).
Improving your car’s gear ratio will give you a mechanical advantage, not to mention, a little power-too-boot when you put your foot on the gas. Gear ratios can be changed in many types of cars, but most people who invest in this upgrade are interested in improving their vehicle’s torque, power, and speed ratio.