Tire & Gear Calculators

Ever wonder how far off your speedometer is with your new bigger tires? Approximate your corrected speed.  Measure from the ground to the center of the axle and multiply by 2 to get your tire diameter. 

  Speedo converter 

Original Tire Diameter:  
New Tire Diameter:  

Speedometer Reading (MPH): 

Corrected Speed (MPH):

Your new, bigger tires are robbing you of power and gas mileage.  What gear ratio will get you back to where you started?    

  Find new Gear Ratio with new tire size 

New Tire Diameter:  
Old Tire Diameter:  

Current Gear Ratio: 

New Gear Ratio:
 

What’s your crawl ratio?   

  Crawl Ratio 

Transmis Ratio: TCase Ratio: Axle Ratio: 

Overall Ratio:

Actual MPH based on gear ratios.   

  MPH Calculation 

RPM:  Tire Diameter:  
Axle Ratio: Transmis Ratio: TCase Ratio: 

MPH: 

How accurate is your Tachometer?   

  RPM Calculation 

MPH: Axle Ratio: Transmis Ratio: TCase Ratio:  
Tire Diameter: 

RPM: 

What size tire do I have?     

  P-Metric tire to inches 

Example: 195/75R15
/ R 

Tire Diameter:




These calculators created by Mark Medina - http://www.4lo.com/