Speedometer check calculator. Solve for Original Tire Diameter. Solve for New Tire Diameter. Solve for Original Speedometer MPH. Solve for New Speedomter MPH (adjusted).
Ever wonder how far off your speedometer is with your new bigger tires? I'm using a simple ratio calculation, so this info will only approximate your corrected speed and depends on the accuracy of tire size diameters (assumimg nothing but tire size has changed). If you know specific information about your vehicle (gear ratios, RPM, etc.) then use the Gear Ratio calculator, it's probably a little more accurate.
(New Tire Diameter / Old Tire Diameter) * Speedometer MPH = Actual MPH