Tire and Gear Calculators

When entering tire diameters, take into consideration the static loaded radius of the tire, not the overall manufacturers published diameter. For example, at correct pressure, my 32" BFG Mud Terrains have a static loaded radius of 14.625 inches. This gives an effective diameter of 29.25 inches.
For accurate results, measure from the ground to the center of the axle, and multiply by 2 then enter that value into the calculators.
This height can change depending on tire pressure (aired up on the street, and aired down off-road) and the speed of the vehicle (centrifugal force on the tire carcass).
MPH Calculations
Tire Diameter:  
Transmission Gear:   
Transfer Case Gear:   
Axle Ratio:  MPH:
RPM Calculations
Tire Diameter:  
Transmission Gear:  
Transfer Case Gear:  
Axle Ratio: RPM:
Speedometer Error
Original Tire Diameter:  
New Tire Diameter:  
Speedometer Reading (MPH): Speed (MPH):
Crawl Ratio
Transmission Gear:  
Transfer Case Ratio:  
Axle Ratio: Crawl Ratio:
P-Metric tire to inches
Example: 195/75R15
LT /  
Tire Diameter:

These calculators are based on code created by Mark Medina - http://www.4lo.com/

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