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The Daily Insight

How do you calculate driven gear?

Author

Sarah Duran

Updated on February 15, 2026

How do you calculate driven gear?

The gear ratio is calculated by dividing the output speed by the input speed (i= Ws/ We) or by dividing the number of teeth of the driving gear by the number of teeth of the driven gear (i= Ze/ Zs).

How do I choose a speedometer gear?

What gears should I get?

  1. Count the teeth on the speedometer drive gear.
  2. Find the gear ratio for the drive axle.
  3. Calculate tire revolutions per mile.
  4. Calculate the required tooth count for the driven gear.
  5. Get the Driven Gear (for your transmission) with the closest tooth count to your calculations.

How do I slow down my speedometer?

“If you need to slow down the speedometer, you need more teeth on the driven gear.” For example, if your speedometer is showing 60 mph and it should be showing 52 mph, you will need to use a driven gear with more teeth to spin the speedometer cable slower. In this case, you need to add three teeth.

How do I know my tire gear ratio?

Here’s the formula for calculating gear ratio: (RPM x Tire Diameter Inches) / (Final Drive Ratio x Transmission Gear Ratio x 336) = Actual numerical gear ratio to the ground from every revolution of the engine.

Do gear ratios add or multiply?

For example, for the gear at left the blue gears are 7 and 21 teeth, while the green gears are 9 and 30 teeth. Thus, the first gear ratio is 7:21 and the second is 9:30. Multiplying the two together gives (7×9):(21×30) = 63 : 630, which is 1:10.

How do you calculate the number of teeth in gear ratios?

Divide the number of driven gear teeth by the number of drive gear teeth. In our example, it’s 28/21 or 4 : 3. This gear ratio shows that the smaller driver gear must turn 1,3 times to get the larger driven gear to make one complete turn.

Does changing gear ratio affect speedometer?

Speedometer and odometer are fed by a signal generator that counts axle revolutions. Just changing axle gears doesn’t affect it.

How do I recalibrate my speedometer?

Press and hold the calibration button located on the speedometer, start the vehicle, and then release the button. Press that button again and then take the test drive. Once you have driven the distance needed, press the button once more and the speedometer will calibrate itself to accommodate the new tire size.

Does putting bigger wheels on your car affect the speedometer?

You might ask: do bigger tires make your speedometer faster? The answer is no. Tire size and speedometer accuracy are directly linked to each other. Up-sizing, or installing a taller tire, will lead to a speedometer reading that is slower than your actual speed.

Can my speedometer be wrong?

Speedometers can show the wrong speed There are several factors that can cause a speedometer to show a speed that is incorrect. One major factor is the age of the car, as many times older vehicles with a lot of miles and wear on them will have speedometers that are not as exact as they used to be.

Do bigger tires raise or lower gear ratio?

When changing gears for taller tires, you are heading to a numerically higher gear ratio. The higher the gear ratio, the smaller the pinion gear. You do not want go too low in an effort to increase power to the wheels and/or relieve stress in the rest of the drivetrain.

What is a good gear ratio for highway driving?

For on-highway linehaul, the range tightens to a fuel friendly 2.26 through 3.42 for the most common ratios. “For on-highway, direct drive, it starts all the way down at 2.26 and up to 3.08 or larger,” Garrison says. “Getting into the mid- and upper-threes is starting to get more unusual these days.”