Interactive Analysis Tool

Tire Size Decoder

Stop guessing what the cryptic numbers on your sidewall mean. Use our interactive visualizer to decode your tire's precise measurements, structural type, and rim compatibility instantly.

Select Your Tire Size

Choose the dimensions from your tire's sidewall below.

/
R
225
Tread WidthMillimeters
/
45
ProfilePercentage
R
BuildRadial
17
Rim Dia.Inches
91Y
Load/SpeedRating

225Section Width

The width of the tire from sidewall to sidewall in millimeters. Your tire is exactly 225mm wide (approx. 8.9 inches). Wider tires provide more lateral grip and shorter braking distances, but can decrease fuel economy due to higher rolling resistance.

45Aspect Ratio

The height of the tire's sidewall expressed as a percentage of the width. Here, the sidewall height is 45% of 225mm, which equals 101.3mm (4.0 inches).

RConstruction

The "R" stands for Radial construction. Over 98% of modern passenger vehicle tires are radial, meaning the internal ply cords radiate outwardly from the center of the tire. This provides superior tread life and steering precision.

17Wheel Diameter

This indicates the size of the wheel (or rim) that the tire is designed to fit, measured in inches. This specific tire must be securely mounted on a 17-inch rim.

The Anatomy of a Tire Size

The string of alphanumeric characters embossed on the side of your tire might look like an arbitrary factory code, but it is actually a standardized global measurement system. Understanding this code is the single most important skill when it comes to maintaining your vehicle's safety, handling characteristics, and speedometer accuracy.

1Section Width

Measured in millimeters, this is the distance from the widest point of the tire's outer sidewall to the widest point of its inner sidewall. A wider tire (e.g., 275mm vs 225mm) provides a significantly larger contact patch. This translates to vastly improved dry cornering grip and shorter braking distances, though it may slightly reduce fuel economy due to increased rolling resistance.

2Aspect Ratio

This is arguably the most misunderstood number. It is not a direct measurement, but a percentage. A 45 aspect ratio means the sidewall's height is exactly 45% of the tire's width. Lower aspect ratios (e.g., 30 or 35) create "low-profile" tires, which offer stiffer sidewalls for sharper, more responsive steering but yield a firmer, less forgiving ride over bumps.

Beyond Dimensions: Load Index and Speed Rating

While our interactive decoder above visualizes the physical dimensions of the tire, there is almost always a suffix at the end of the size string, such as 91Y, 104T, or 88V. These two characters are critical for your safety.

Load Index (The Number)

The load index (e.g., 91) corresponds to a standard chart indicating the maximum weight that a single tire can safely support when fully inflated. For example, an index of 91 means the tire can carry exactly 615 kg (1,356 lbs). Never replace your factory tires with a lower load index.

Speed Rating (The Letter)

The speed rating (e.g., Y, V, W) indicates the maximum speed the tire can safely sustain over time without risking structural failure due to heat buildup. A 'V' rating means up to 149 mph, while a 'Y' rating is certified up to 186 mph.

Ready to Explore Upgrades?

Now that you understand exactly how to read your current tire size, you have the knowledge needed to safely explore modifications. Use our advanced 3D visualizer to compare your factory size against potential upgrades.

Launch 3D Comparison Calculator