What Do Numbers on Tire Mean? Complete Guide
Confused by all the numbers on your tire? This comprehensive guide explains every number and code, so you can understand exactly what your tire specifications mean.
Quick Example: 205/55R16 91V
Every number and letter has a specific meaning. Let's break down what each part means in this complete guide.
Understanding Tire Size Numbers: 205/55R16
The most prominent numbers on your tire represent the size specifications. Let's decode a typical example: 205/55R16
205 - Tire Width
This number represents the tire's width in millimeters from sidewall to sidewall when mounted and inflated.
- 205mm = approximately 8.07 inches
- Common widths range from 155mm to 355mm
- Wider tires generally provide better grip and stability
- Must match your vehicle's specifications
55 - Aspect Ratio
This number is the aspect ratio or profile of the tire. It represents the height of the sidewall as a percentage of the tire width.
- 55 means the sidewall height is 55% of 205mm = 112.75mm
- Lower numbers (e.g., 35, 40) = lower profile, sportier look
- Higher numbers (e.g., 65, 70) = taller sidewall, more comfort
- Affects ride comfort, handling, and appearance
R - Construction Type
The letter indicates the tire's construction type.
- R = Radial (most common, 98% of tires)
- B = Belted Bias
- D = Diagonal (bias-ply, older type)
- Radial tires offer better fuel efficiency and longer tread life
16 - Rim Diameter
This number indicates the rim diameter in inches that the tire is designed to fit.
- 16 = 16-inch rim diameter
- Common sizes: 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 inches
- Must exactly match your wheel size
- Wrong size = dangerous and won't fit properly
Additional Numbers: Load Index and Speed Rating
91 - Load Index
The load index number indicates the maximum weight capacity of a single tire at maximum inflation pressure.
Important: Multiply by 4 for total vehicle capacity
V - Speed Rating
The speed rating letter indicates the maximum safe speed the tire can sustain under ideal conditions.
DOT Code Numbers: Production Date
The DOT code contains numbers that indicate when your tire was manufactured. The last 4 digits are the most important.
Example: DOT ABCD 4523
Week Number (First 2 digits)
45 = Week 45 of the year
Year (Last 2 digits)
23 = Year 2023
Complete Date: Week 45 of 2023 (approximately November 2023)
Other Numbers You Might See
Treadwear Rating
Usually a 3-digit number like "300" or "500". Higher numbers indicate longer-lasting tread. However, this is a relative rating, not an exact mileage prediction.
Traction Rating
Single letter rating (AA, A, B, C) indicating wet traction performance. AA is the highest rating.
Temperature Rating
Single letter (A, B, C) indicating the tire's ability to dissipate heat. A is the highest rating.
Complete Example Breakdown
205/55R16 91V205
Width: 205mm (8.07 inches)
55
Aspect Ratio: 55%
R
Construction: Radial
16
Rim: 16 inches
91
Load: 615 kg (1,356 lbs)
V
Speed: 149 mph (240 km/h)
Why These Numbers Matter
Safety
Correct size and specifications ensure safe vehicle operation and optimal performance.
Cost Efficiency
Right tires improve fuel economy and reduce premature wear, saving money long-term.
Legal Compliance
Proper specifications ensure your vehicle meets safety and legal requirements.
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