How to Read Your Tire Size (and P-Metric vs. Metric)
The string of numbers on your tire's sidewall is all you need to buy the right replacement. Once you can read it, you can shop for tires anywhere — including in Thailand, where the format may look slightly different from what you're used to at home.
Reading 215/55R17 94V, piece by piece
| Part | Meaning |
|---|---|
| 215 | Tire width in millimeters |
| 55 | Aspect ratio — the sidewall height is 55% of the width (about 118 mm here) |
| R | Radial construction (almost every car tire today) |
| 17 | Wheel (rim) diameter in inches |
| 94 | Load index — the maximum load per tire |
| V | Speed rating — the maximum sustained speed |
Where to find your size
- The sidewall of the tires on your car — the most reliable source, because a previous owner may have changed the wheels.
- The sticker inside the driver's door — the factory size and the recommended pressure.
- The owner's manual.
Can't read it? Send a photo of your sidewall to LINE @subphaisal and our team will tell you the size.
P-metric (US) vs. metric (Thailand)
Tires sold in the US often start with a letter: P225/65R17 is a passenger tire built to the US “P-metric” standard. In Thailand, almost every passenger tire uses the metric standard with no letter: 225/65R17. The width, sidewall height and wheel size are the same, so the tire fits the same wheel.
The difference is in how the load rating is calculated, which varies slightly between the two standards. The rule is simple: choose a tire with the same or a higher load index than the one your car came with.
- LT at the start (for example LT265/70R17) means a light-truck tire with heavier construction. Replace like with like.
- C at the end (for example 215/70R15C) means a commercial tire for carrying loads — common on Thai pickups used for work.
- XL means Extra Load: the tire carries more weight at a higher pressure than a standard tire of the same size.
Load index and speed rating
The two characters after the size tell you how much weight each tire can carry and how fast it can safely go. Common values:
| Load index | Max load per tire |
|---|---|
| 91 | 615 kg |
| 94 | 670 kg |
| 98 | 750 kg |
| 102 | 850 kg |
| 112 | 1,120 kg |
| Speed rating | Max speed |
|---|---|
| T | 190 km/h |
| H | 210 km/h |
| V | 240 km/h |
| W | 270 km/h |
| Y | 300 km/h |
A replacement tire should match or exceed both numbers on your door sticker. A higher speed rating is fine; a lower load index is not.
Can you change to a different size?
Owners sometimes fit larger wheels with lower-profile tires, or go the other way for a softer ride. It can work when the overall diameter stays close to the original and the tire clears the suspension and wheel arch. A different diameter changes your speedometer reading and can confuse ABS and stability control, so ask us before you switch.
Now find your tires
Search by size on our tire page, or check the factory sizes for popular cars in Thailand. Before you buy, it's also worth knowing how to read the production date.
Frequently asked questions
What does 215/55R17 mean?
215 is the tire width in millimeters, 55 is the sidewall height as a percentage of the width, R means radial construction, and 17 is the wheel diameter in inches.
Where can I find my tire size?
On the sidewall of your current tires, and on the sticker inside the driver's door, which also lists the recommended tire pressure. The owner's manual has it too.
Is P225/65R17 the same as 225/65R17?
The dimensions are the same. The P marks a US-standard passenger tire; tires sold in Thailand use the metric standard without the letter. Load ratings are calculated slightly differently between the two, so choose a tire with the same or higher load index than your current one.
What do the numbers and letter after the size mean?
In 94V, 94 is the load index (670 kg per tire) and V is the speed rating (up to 240 km/h). Replacement tires should match or exceed both.
Can I fit a different tire size?
Sometimes, if the overall diameter stays close to the original and the tire fits the wheel and the wheel arch. Ask us before changing size — a mismatched size can upset the speedometer and the car's safety systems.
What does XL mean on a tire?
XL (Extra Load) means the tire is built to carry more weight at a higher pressure than a standard-load tire of the same size. If your car came with XL tires, replace them with XL tires.