Tyre Markings
Decoding the Information on Your Tyre Sidewall
Take a close look at your tyre sidewall — you’ll notice a sequence of numbers, letters, and symbols. Far from random, these markings provide a complete technical profile of your tyre.
They indicate its size, construction type, load and speed capacity, and even when it was manufactured. Understanding these details ensures you select the right replacement tyres for your vehicle and maintain optimal safety, performance, and fuel efficiency.
Example: 225/45 R 18 95 H
Let’s decode this step by step.
1. Tyre Width – “225”
The first number, 225, represents the nominal width of the tyre in millimetres.
It measures the distance from one sidewall to the other when the tyre is properly mounted and inflated.
Example: A 225 tyre is approximately 225 mm wide from edge to edge.
2. Aspect Ratio – “45”
The next number, 45, is the aspect ratio — the height of the tyre’s sidewall expressed as a percentage of its width.
In this example: The height of the tyre’s sidewall is 45% of 225 mm, which equals about 101 mm.
A lower aspect ratio means a shorter sidewall, providing sportier handling and quicker steering response, while a higher ratio offers a more comfortable ride.
3. Construction Type – “R”
The letter following the aspect ratio indicates the tyre’s internal construction.
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R = Radial (most common type today)
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B = Bias-ply
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D = Diagonal-ply
In a radial tyre, the internal ply cords run perpendicular (at 90°) to the direction of travel, from bead to bead. This design provides flexibility, better heat dissipation, and improved fuel efficiency — which is why nearly all modern tyres are radial.
4. Rim Diameter – “18”
The next number, 18, is the diameter of the wheel rim the tyre fits — measured in inches.
Example: “18” means this tyre fits an 18-inch wheel.
This measurement must exactly match your vehicle’s wheel size.
5. Load Index – “95”
The load index is a numerical code that specifies the maximum weight the tyre can carry when inflated to its correct pressure.
For example, 95 corresponds to a maximum load of 690 kg per tyre.
Passenger-car load indices typically range from 75 (387 kg) to 105 (925 kg).
Refer to your vehicle’s documentation or the manufacturer’s load index chart for exact values.
6. Speed Rating – “H”
The final letter in the sequence indicates the maximum safe speed the tyre can sustain under its rated load capacity.
| Letter | Max Speed (km/h) | Approx. mph |
|---|---|---|
| T | 190 | 118 |
| H | 210 | 130 |
| V | 240 | 149 |
| W | 270 | 168 |
| Y | 300 | 186 |
| (Y) | >300 | >186 |
In our example, H means the tyre is certified for speeds up to 210 km/h (130 mph).
Even so, always obey your country’s legal speed limits and drive within safe conditions.
Additional Tyre Markings
Beyond the standard size and performance information, several other markings appear on the sidewall. Here’s what they mean:
| Marking | Meaning |
|---|---|
| 7. Self-Supporting Run-Flat (SSR) | Indicates the tyre is designed to remain drivable for a limited distance after a puncture. |
| 8. MO (Mercedes Original) | Manufacturer approval mark – confirms the tyre was developed to OEM specifications (e.g., MO for Mercedes, AO for Audi, N for Porsche, etc.). |
| 9. M+S | “Mud and Snow” – denotes suitability for light winter conditions. For severe snow, look for the 3PMSF symbol. |
| 10. DOT | Certification from the U.S. Department of Transportation, ensuring compliance with U.S. safety standards. |
| 11. Week of Manufacture | The first two digits of the final code (e.g., 2319) indicate the week the tyre was made — week 23 in this case. |
| 12. Year of Manufacture | The last two digits of the same code (e.g., 2319) show the year — 2019 in this example. |
Tip: Tyres older than six years should be inspected regularly, even if unused, and those over ten years are generally due for replacement, regardless of tread depth.
Summary: What Each Marking Means
| Section | Example Value | Meaning |
|---|---|---|
| Tyre Width | 225 | Width in mm |
| Aspect Ratio | 45 | Height is 45 % of width |
| Construction | R | Radial structure |
| Rim Diameter | 18 | Fits 18-inch wheel |
| Load Index | 95 | Max load 690 kg per tyre |
| Speed Rating | H | Max speed 210 km/h |
| Other Codes | SSR, M+S, MO, DOT, 2319 | Run-flat, winter use, OE spec, compliance, date |
In Summary
Understanding tyre sidewall markings empowers you to:
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Select the correct replacements
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Ensure optimal safety, performance, and fuel efficiency
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Confirm compliance with manufacturer specifications
Before purchasing new tyres, always match the size, load index, and speed rating recommended in your vehicle’s manual.