Overall Gear Ratio with Tire Size Calculator

Larger tires effectively lower your gear ratio, reducing acceleration but improving top speed and fuel economy. Smaller tires have the opposite effect, creating a higher effective gear ratio with better acceleration but lower top speed.

The effective gear ratio is your actual final drive ratio after accounting for tire size changes. It's calculated by multiplying your differential gear ratio by the ratio of stock tire diameter to new tire diameter.

Not necessarily, but changing to a numerically higher gear ratio can restore your original performance characteristics. This is especially important with significantly larger tires to maintain acceleration and reduce stress on the drivetrain.

Tire diameter = (2 × sidewall height) + rim diameter. Sidewall height = (tire width × aspect ratio) / 25.4. For example, a 235/70R16 tire has a diameter of approximately 28.0 inches.

Use the 'New Gear Ratio Needed' result to maintain stock performance. For better acceleration with larger tires, choose a slightly higher numerical ratio. For highway driving, you might prefer keeping the lower effective ratio.

No, gear ratio changes don't affect speedometer accuracy. However, the tire size change that prompted the gear ratio change will affect speedometer readings. Larger tires make the speedometer read slower than actual speed.

Ring and pinion gear ratio refers to your differential's final drive ratio - the ratio between the ring gear teeth and pinion gear teeth. Common ratios include 3.08, 3.31, 3.55, 3.73, 4.10, and 4.56.