Rollout

Definition of rollout: Rollout is how far a car will travel with one revolution of the armature, often referred to as the rollout ratio. A larger number indicates a faster top speed/less torque and a smaller number indicates slower top speed/more torque.

Formula: Rollout = ( Tire Diameter * pi ) / Final Drive Gear Ratio pi is 3.141592654

To keep things simple, all you really need to know is: Rollout is how far a car will travel with one revolution of the armature.


Rollout Calculator

The calculator below will allow you to determine the rollout ratio, as well as the gear ratio, based on just a few inputs. Enter the gear and tire sizes you're running and hit the enter key on your keyboard for the results.
Data Input Results
 
Outer Tire Diameter

Spur Gear
Pinion Gear

 
Rollout

Tire Circumference 
   

Pinion:Spur Ratio    

Rollout                     

What The Results Mean

 The tire circumference is the distance around the tread of a tire. In the default example, the results show it's 2.551 inches around the outside of an .812" diameter tire.

The 8 tooth pinion and 27 tooth spur gears in the example results in a 3.375 to 1 gear ratio. An 8 tooth pinion gear will turn 3.375 times in order to turn the spur gear one time. To put it another way, the motor will turn 3.375 times to turn the axle and tires one time.

The rollout ratio number given is not actually a ratio. It's a distance. In the example, 0.756" is how far the car will travel with one revolution of the armature.