Calculate Tire Size Speed Difference

Speed Difference Formula:

\[ Diff = \frac{RPM \times \pi \times (TD_{new} - TD_{old})}{1056} \]

Speed Difference (mph):

Definition: This calculator estimates the speed difference when changing tire sizes while maintaining the same RPM.

Purpose: It helps vehicle owners and mechanics understand how tire size changes affect speedometer readings and actual vehicle speed.

The calculator uses the formula:

\[ Diff = \frac{RPM \times \pi \times (TD_{new} - TD_{old})}{1056} \]

Where:

Explanation: The formula calculates the speed difference caused by the change in tire circumference at a given RPM.

Details: Proper calculation ensures accurate speedometer readings, proper gearing, and optimal vehicle performance after tire changes.

Tips: Enter the RPM, new tire diameter, and old tire diameter (all in inches). All values must be > 0.

Q1: Why does tire size affect speed?
A: Larger tires cover more distance per revolution, making the vehicle travel faster at the same RPM.

Q2: How do I measure tire diameter?
A: Measure from ground to top of tire when properly inflated or use manufacturer specifications.

Q3: What's the 1056 constant in the formula?
A: It's a conversion factor that combines unit conversions (inches to miles, minutes to hours).

Q4: Does this account for speedometer error?
A: Yes, the difference shows how much your actual speed differs from what your speedometer displays.

Q5: What if my result is negative?
A: A negative result means your vehicle will go slower with the new tires at the same RPM.