16 Nov 2024When you look at the sidewall of your tyres, you’ll likely notice the brand name prominently displayed. But you’ll also see a series of numbers, letters, and symbols. At first, these markings might seem like a foreign language, but understanding them can provide valuable insights into the size, capabilities, and maintenance needs of your tyres.
Here’s a breakdown of essential tyre markings to help you get familiar with them.
1. Tyre Size
The sidewall prominently displays the tyre size, often in a sequence like 205/55 R16 91V.
• Width (205): This number is the tyre width in millimeters, measured from sidewall to sidewall.
• Aspect Ratio (55): This represents the height as a percentage of the tyre’s width. Here, 55 means the height is 55% of the width.
• Construction (R): The “R” stands for Radial, the most common tyre construction type.
• Rim Diameter (16): This indicates the diameter of the wheel rim in inches. In this example, the tyre fits a 16-inch rim.
• Load Index (91): This number refers to the maximum weight the tyre can safely carry, with each index number corresponding to a specific weight. Learn more.
• Speed Rating (V): The letter indicates the tyre’s maximum safe speed when carrying its full load. For instance, a V-rated tyre is rated for up to 240 km/h.
2. DOT Code
The DOT (Department of Transportation) code is used primarily in the U.S. and includes a four-digit date code to show when the tyre was manufactured.
• First Two Digits: Indicate the week of production (01 to 52).
• Last Two Digits: Show the year of production.
For example, a DOT date code of 4722 means the tyre was made in the 47th week of 2022. Tyres over six years old may be more prone to wear and damage, so keeping track of tyre age is essential.
3. Maximum Load and Pressure Markings
The sidewall displays MAX LOAD and MAX PRESS values, which indicate the tyre’s maximum load capacity and pressure. These are not the recommended settings for your vehicle but are the upper limits of the tyre. For safe performance, always follow your vehicle’s recommended tyre pressure, found in the owner’s manual or on a sticker in the driver’s door frame or fuel cap.
• Why Correct Tyre Pressure Matters:
o Fuel Efficiency: Proper pressure reduces rolling resistance.
o Longevity: Helps prevent uneven wear and extends tyre life.
o Safety: Ensures stability, braking efficiency, and traction.
4. Tread Wear Indicators (TWI)
Most tyres have small raised bars, or “wear indicators,” built into the tread grooves. When the tread wears down to these bars (typically 1.5mm), it’s time to replace the tyre.
• A tread depth gauge can help you measure tread precisely. New tyres usually have around 8-9mm of tread.
• Uneven wear patterns (e.g., more wear on the inner or outer edge) can signal alignment or suspension issues.
• Cracks, bulges, or other visible damage also mean the tyre should be replaced.
5. Additional Tyre Markings
Tyres are available in a variety of types to suit specific needs, with sidewall markings that detail their characteristics. Here are some common ones:
• M+S (Mud and Snow): Indicates traction in mud and snow, though not necessarily rated for severe winter conditions.
• 3PMSF (Three Peak Mountain Snowflake): A snowflake within a mountain symbol, indicating the tyre meets performance requirements for severe winter driving.
• Run-Flat Markings: Abbreviations like “RFT” signal that the tyre can function for a limited distance at reduced speed after a puncture. Learn more.
• XL (Extra Load): Signifies the tyre can carry a higher load than standard tyres, essential for heavier vehicles.
• High-Performance: Markings like “HP” or “UHP” indicate enhanced handling and speed capabilities.
• OE (Original Equipment): This indicates the tyre was specifically designed for a certain vehicle brand, ensuring optimal performance.
Being able to read these markings is a useful skill, helping you select the right tyres, maintain them properly, and know when to replace them. Matching tyres to your vehicle’s specifications is essential for safety, performance, handling, and tyre longevity.
