Tire Size Calculator

Compare tire sizes and visualize differences in performance and speedometer accuracy.

Tire Comparison

Compare dimensions and speedometer impact between two tire setups.

Original Setup

Width / Aspect R / Rim

Alternative Setup

Width / Aspect R / Rim

Waiting for dimensions...

Enter tire codes on the left to begin analysis.

Understanding the Tire Size Calculator

Compare the dimensions, circumference, and speedometer impact of two different tire setups. Essential for anyone looking to upgrade wheels or change tire profiles while maintaining vehicle safety standards.

Guide

How to use the Tire Size Calculator

1Enter the 'Original Setup' dimensions found on your current tire sidewall (e.g., 205/55 R16).
2Input the 'Alternative Setup' dimensions you are considering.
3Press 'Analyze Differences' to view the comparative report.
4Check the 'Size Variance' percentage. Experts generally recommend staying within ±3% of the original diameter.
5Observe the 'Speedometer Change' to understand how your dash reading will differ from your actual speed.

Applications

Common Use Cases

Aftermarket Wheels: Ensuring new wheels and tires don't rub or interfere with the suspension.

Winter Tires: Finding a narrower winter setup that maintains the correct diameter.

Off-Roading: Calculating the lift achieved by switching to larger diameter tires.

Speedometer Calibration: Understanding why your speedometer might be inaccurate after a tire swap.

The Maths Behind the Calculation

Diameter = (Width × Ratio / 1270) + Rim

Tire diameter is calculated by adding the rim size to twice the sidewall height. Sidewall height is the tire width multiplied by the aspect ratio (as a percentage).

Knowledge Base

Frequently Asked Questions

What is the 3% rule for tires?

The 3% rule suggests that your new tire diameter should be within ±3% of the original setup to avoid significant issues with the speedometer, braking systems (ABS), and transmission gearing.

How does a larger tire affect my speedometer?

A larger diameter tire has a greater circumference, meaning it travels further with each rotation. This results in your speedometer reading a slower speed than you are actually traveling.

What does the 'R' in tire size mean?

The 'R' stands for Radial, which refers to the tire's internal construction method. It is not related to the radius of the wheel.

Regional Notice: United States

"Federal tax estimates are based on 2024 brackets. Consult a tax professional for official filing."

Loading calculator...