Written by City Wheels · G-10/1, Islamabad
- tyre-size
- guide
- buying
A tyre size such as 205/55 R16 91V tells you five things: the tyre is 205 mm wide, its sidewall height is 55% of that width, it has radial construction, it fits a 16-inch rim, and it can carry 615 kg at speeds up to 240 km/h. The size on your car's door placard is the one to match.
What does each part of a tyre size mean?
| Part | Example | Meaning |
|---|---|---|
| Section width | 205 | Width of the tyre in millimetres, sidewall to sidewall |
| Aspect ratio | 55 | Sidewall height as a percentage of the width |
| Construction | R | Radial — virtually every modern car tyre |
| Rim diameter | 16 | The wheel size it fits, in inches |
| Load index | 91 | Maximum load per tyre (91 = 615 kg) |
| Speed rating | V | Maximum sustained speed (V = 240 km/h) |
How tall is the sidewall?
Multiply the width by the aspect ratio. A 205/55 tyre has a sidewall of about 113 mm (205 × 0.55). A 195/65 tyre has about 127 mm. A taller sidewall absorbs more of a pothole and rides more softly; a lower one sharpens steering but protects the rim less.
What do the load index and speed rating mean?
The load index is a code for the maximum weight each tyre can carry when correctly inflated. The speed rating is the maximum speed the tyre is built to sustain. Never fit a tyre with a lower load index or speed rating than your vehicle's placard specifies — it matters most on heavy cars, loaded long trips and hot motorway runs.
| Load index | Max load per tyre | Speed rating | Max speed |
|---|---|---|---|
| 79 | 437 kg | S | 180 km/h |
| 82 | 475 kg | T | 190 km/h |
| 88 | 560 kg | H | 210 km/h |
| 91 | 615 kg | V | 240 km/h |
| 95 | 690 kg | W | 270 km/h |
| 102 | 850 kg | Y | 300 km/h |
How do I tell how old a tyre is?
Find the DOT code on the sidewall. The last four digits are the week and year of manufacture: 2823 means week 28 of 2023. Tyre rubber hardens with age even if the tyre has hardly been used, which is why age matters as much as tread when deciding when to replace a tyre.
Where do I find the right size for my car?
Check the placard on the driver's door frame (sometimes inside the fuel flap). It lists the original tyre size and recommended pressures. Trust it over the tyres currently fitted — a previous owner may have changed size. Common fitments include 195/65 R15 on many Corollas and 205/55 R16 on the Civic.
Can I fit a different size?
Sometimes. Moving to a different width or rim size is fine if the overall diameter stays within about 3% of the original, the load index and speed rating are at least as high, and the tyre clears the suspension and arch at full lock. Get it wrong and your speedometer reads incorrectly. Ask us before you buy — we will check it on your car.
Questions answered
What does the R mean in a tyre size?
R stands for radial construction, meaning the cord plies run radially across the tyre. It does not mean radius, although the number after it is the rim diameter in inches.
Is a higher load index better?
A higher load index means the tyre can carry more weight, but it does not make the tyre better for a light car. What matters is that it meets or exceeds the figure on your door placard; going below it is unsafe.
