Tire Size Comparison Calculator
Compare two tire sizes side-by-side and see the difference in dimensions and speedometer readings.
Comparing Tire Sizes: What You Need to Know
Changing your tire size, a practice often called "plus-sizing" or "up-stepping," can significantly alter your vehicle's appearance, handling, and performance. The Tire Size Comparison Calculator is an essential tool that allows you to compare two different tire sizes, providing a detailed breakdown of the differences in their physical dimensions and, crucially, the impact on your speedometer's accuracy.
How to Read a Tire Code
Car tires are described by an alphanumeric code, as shown in the figure below. Being able to read the tire code can be important, particularly when considering getting new wheels or tires, as being able to read the tire code is necessary for calculating things like tire size. Each part of the code describes some characteristic of the tire; refer to the figure below.
⚙️ How to Use the Comparison Calculator
- Enter Tire 1 (Original): In the first set of boxes, input the width, aspect ratio, and wheel diameter of your current or original tires.
- Enter Tire 2 (New): In the second set of boxes, input the specifications for the new tire size you are considering.
- Calculate: Click the "Compare Tires" button or press Enter on your keyboard to generate the comparison.
The calculator will provide a comprehensive report including a side-by-side visual representation, a table comparing the numerical dimensions with percentage differences, and a speedometer difference chart.
Understanding the Results
The comparison is broken down into three key sections:
- Visual Representation: A side-by-side diagram helps you intuitively see the difference in the overall size of the two tires.
- Numerical Comparison Table: This table provides the most important data, showing the exact dimensions (Tire Height, Sidewall Height, Width, etc.) for both tires and the percentage difference between them. The percentage difference for tire height is the most critical metric.
- Speedometer Difference Chart: This chart shows how your actual speed will change with the new tires. If Tire 2 has a larger diameter than Tire 1, your actual speed will be faster than your speedometer indicates. If it's smaller, your actual speed will be slower.
A general rule of thumb in the automotive community is to keep the difference in overall tire diameter within +/- 3% of the original size. Exceeding this can lead to issues with your vehicle's anti-lock braking system (ABS), traction control, and transmission shifting points, in addition to significant speedometer error. This calculator helps you stay within that safe tolerance.
💡 Frequently Asked Questions (FAQ)
- Why does changing tire size affect my speedometer?
- Your vehicle's speedometer is calibrated to the original tire's circumference. It measures speed by counting how many times the tire rotates. If you install a larger tire, it covers more ground with each rotation, so your actual speed will be faster than what the speedometer shows. The opposite is true for smaller tires.
- Will a wider tire fit my car?
- Not necessarily. While this calculator compares dimensions, it cannot account for your specific vehicle's wheel well clearance, suspension components, or wheel offset. A significantly wider tire may rub against these components, which is unsafe. Always consult a professional tire shop before making a final decision.
- Where can I find other tire-related calculations?
- For more detailed analysis of a single tire or to explore alternative sizes for a new wheel, please visit our primary Tire Size Calculator.