Every tire has its size moulded into the sidewall. To search SellMyTires you only need the first three numbers: width, aspect ratio and rim diameter.
- P Tire typeP = passenger, LT = light truck. Often omitted.
- 225 WidthTread width in millimetres.
- 45 Aspect ratioSidewall height as a % of the width.
- R ConstructionR = radial (almost every modern tire).
- 17 Rim diameterFits a 17-inch wheel.
- 94 Load index94 = 670 kg (1,477 lb) per tire.
- H Speed ratingH = up to 210 km/h (130 mph).
Where to find it
- On the tire. Look along the sidewall for a code like 225/45R17.
- On the vehicle placard. Usually on the driver’s door jamb, it lists the size the vehicle came with.
- In the owner’s manual. Some vehicles use different sizes front and rear.
What each part means
| Part | Example | Meaning |
|---|---|---|
| Tire type | P / LT | P = passenger, LT = light truck, T = temporary spare. Often left off. |
| Width | 225 | Width of the tread in millimetres, sidewall to sidewall. |
| Aspect ratio | 45 | Sidewall height as a percentage of the width (45% of 225 mm ≈ 101 mm). |
| Construction | R | Radial. Almost every modern tire is radial. |
| Rim diameter | 17 | Wheel size in inches the tire fits. |
| Load index | 94 | Maximum load per tire. 94 = 670 kg (1,477 lb). |
| Speed rating | H | Maximum sustained speed. H = 210 km/h (130 mph), V = 240 km/h (149 mph), W = 270 km/h (168 mph). |
Tire age: the DOT date code
Near the size you’ll find “DOT” followed by letters and numbers. The last four digits are the week and year the tire was made: 2321 means week 23 of 2021.
Rubber ages even when a tire isn’t used. Many tire and vehicle makers recommend having tires inspected yearly after about 5 years and replacing them by around 10 years old, whatever the tread looks like. Follow your vehicle and tire maker’s guidance.
Tread depth
Tread is measured in 32nds of an inch. New tires usually start around 10/32″ to 12/32″.
- 2/32″ (1.6 mm) is the legal minimum in most U.S. states. Rules differ across Canadian provinces, so check yours.
- Wet-road grip drops noticeably well before that; many drivers replace at 4/32″.
- For snow, more depth matters. Winter tires are often replaced around 5/32″ to 6/32″.
Changing size? A different size can affect speedometer accuracy, clearance, ABS and stability systems. Ask a tire shop before switching from your vehicle’s original size.