Tire Size Calculator

Most manufacturers recommend staying within 3% of your original tire diameter. Going beyond this can affect speedometer accuracy, ABS function, traction control, and fuel economy. Changes greater than 5% may cause clearance issues with your fenders or suspension.

Yes. Larger tires mean your speedometer will read slower than your actual speed. For example, if your new tires are 3% larger in diameter, when your speedometer shows 100 km/h, you are actually traveling at 103 km/h. This calculator shows the exact speedometer error at various speeds.

Plus sizing is a method of upgrading to larger wheels while maintaining approximately the same overall tire diameter. When you go up one inch in wheel size (plus 1), you typically decrease the aspect ratio by 10% and increase width by 10mm. This improves handling while keeping speedometer accuracy.

Yes, but with considerations. You can use different tire sizes as long as: (1) they fit your wheels, (2) they clear your fenders and suspension, and (3) the overall diameter stays within 3% of stock. Our calculator helps you compare sizes and see if your choice is within safe limits.

The aspect ratio is the second number in a tire size (e.g., the "55" in 205/55R16). It represents the sidewall height as a percentage of the tire width. A 205/55R16 tire has a sidewall height that is 55% of 205mm, which equals approximately 113mm.

Use our tire size calculator to compare your current tire size with the new size. Check that: (1) the wheel diameter matches your wheels, (2) the overall diameter is within 3% of your original tires, and (3) the width will clear your fenders. For vehicle-specific fitment, use our vehicle selector.

Wider tires generally provide better grip and handling due to increased contact patch with the road. However, they can also increase road noise, reduce fuel economy, and cause hydroplaning in wet conditions. The trade-off depends on your driving conditions and priorities.

For all-wheel drive (AWD) vehicles, it is strongly recommended to replace all four tires at once to prevent drivetrain damage. For front-wheel or rear-wheel drive vehicles, you can replace tires in pairs (front or rear), but all four tires should ideally be the same size and type.

P-metric tires (marked with "P" before the size, like P225/65R17) are designed for passenger vehicles and prioritize comfort and fuel efficiency. LT (Light Truck) tires are built with stronger sidewalls and higher load capacities for trucks and SUVs that carry heavy loads or tow trailers. LT tires have stiffer sidewalls which can result in a firmer ride.

Larger, wider, or heavier tires typically reduce fuel economy because they increase rolling resistance and require more energy to rotate. A tire that is 3% larger in diameter can decrease fuel economy by 1-2%. Conversely, narrower tires with lower rolling resistance can improve fuel efficiency by up to 3-5%.

Mixing tire sizes is generally not recommended, especially on all-wheel drive vehicles where different tire diameters can damage the drivetrain. Some performance vehicles are designed with staggered setups (wider rear tires), but this should only be done if specified by the manufacturer. Always consult your owner's manual before mixing tire sizes.

The "R" in a tire size (like 225/45R17) stands for Radial construction, which is the standard construction method for modern passenger tires. Radial tires have cord plies arranged at 90 degrees to the direction of travel, providing better flexibility, longer tread life, and improved fuel efficiency compared to older bias-ply construction.

To calculate overall diameter: (1) Multiply the width by the aspect ratio divided by 100 to get sidewall height in mm, (2) Multiply sidewall height by 2 (top and bottom), (3) Convert wheel diameter from inches to mm (multiply by 25.4), (4) Add them together. For example, a 225/45R17: Sidewall = 225 × 0.45 = 101.25mm. Diameter = (101.25 × 2) + (17 × 25.4) = 634.3mm.

The load index is a number (like 91 in "91V") that indicates the maximum weight a tire can support when properly inflated. For example, a load index of 91 means the tire can carry up to 615 kg (1,356 lbs). Never replace tires with a lower load index than your vehicle's original equipment tires, as this can be unsafe.

Speed ratings indicate the maximum sustained speed a tire can safely handle. Common ratings include: S (180 km/h), T (190 km/h), H (210 km/h), V (240 km/h), W (270 km/h), and Y (300 km/h). Always match or exceed your vehicle's original speed rating. Using tires with a lower speed rating than recommended can be dangerous at highway speeds.

Winter tires are often available in the same sizes as all-season tires, but some drivers opt for narrower winter tires (10-20mm narrower) because they can cut through snow more effectively and may improve traction on ice. For example, if your summer tires are 225/45R17, you might consider 215/50R17 for winter. Check our calculator to ensure the diameter stays within 3%.

Installing significantly oversized tires may void certain aspects of your vehicle warranty, particularly for drivetrain or suspension components. Tires within 3% of the original diameter are generally safe, but tires that are much larger can cause premature wear on suspension components, affect ABS and traction control systems, and potentially void related warranties. Check with your dealer if unsure.

Tire circumference is the distance around the outside of the tire. It directly affects speedometer accuracy because your vehicle calculates speed based on how many times the tire rotates. A larger circumference means fewer rotations per kilometer, making your speedometer read slower than actual speed. Our calculator shows circumference and revolutions per kilometer for both tire sizes.

The DOT code on your tire sidewall ends with a 4-digit number indicating when the tire was made. The first two digits are the week, and the last two are the year. For example, "2423" means the tire was manufactured in the 24th week of 2023. Tires older than 6 years should be inspected annually, and most manufacturers recommend replacing tires after 10 years regardless of tread depth.