How to Understand Your Vehicle's Tyre Markings
The sidewall of a tyre is marked with a whole range of confusing letters and numbers. This article will ensure you fully understand how to research and buy tyres for your vehicle
How to Understand Your Vehicle's Tyre Markings
It is challenging to understand your tyre markings when you are considering replacing the tyres on your car.
With an increasing number of price comparison sites on the Internet, more and more people are choosing to search for the best deal for replacement tyres themselves.
By the end of this article, you will fully understand what the numbers and letters on the side of your tyre mean, which parts relate to the tyre size, composition dimensions and capabilities.
The tyre size code:
Tyre Size: This vital piece of information can be located on the sidewall of your tyre, it is a series of letters and numbers. An example of what this code looks like is: 205/55R/16/91H.
Tyre Width: The first three numbers that you will see shows the width of the tyre, this is measured in millimetres. With the example above, 205, indicates the tyre width is 205mm.
Aspect Ratio: This is represented with the 4th and 5th digits of the tyre code, coming after the tyre width. Also known as the profile height, the aspect ratio is shown as a percentage of the tyre width. So an aspect ratio of 55, indicates the profile height of the tyre is 55% of its total width.
Radial: If the tyre is a radial tyre, it will be clearly marked with an “R”. This type of tyre is built with the cord piles angled at 90 degrees to the direction of travel, giving extra strength to the tyre.
Wheel Diameter: This indicated the height of the wheel, or, the wheel rim size which the tyre is fitted to, it is always in inches. So a tyre marked 16, will fit an 16-inch wheel rim.
Load Index: The maximum load the tyre is capable of carrying when inflated to the safest maximum pressure. In the example above, it is 91. Both speed and load index ratings should be confirmed together when making a purchase of a tyre. It is vital to always check the manufacturer's recommendations in the vehicle manual to ascertain the load limits.
|Load Index||Load in KG||Load Index||Load in KG||Load Index||Load in KG||Load Index||Load in KG||Load Index||Load in KG|
*The overloading of any vehicle can put undue stress on the vehicle; it can increase your fuel consumption, affect handling, and even cause a catastrophic tyre failure.
Speed Rating: When the tyre is inflated correctly, utilised under its maximum load, the speed rating indicates the maximum speed for the tyre. This is represented by a letter, after the load rating.
|Speed Rating||Miles Per Hour||Kilometers Per Hour|
General Tyre Grading, Markings and Standards
Here is some more, specific information regarding tyre grading and tyre standards which could be useful for you to know about.
- Temperature Grades: A, B and C, with A being the highest. This displays the resistance of the tyre to heat generation as well the capability to dissipate heat. You can find the word tempature and the rating on the sidewall of the tyre. An A grade is best for hot road conditions, B for modearte road conditions and C cold road conditions.
- Traction Grades: The various grades are AA, A, B and C, with AA being the highest grade. These demonstrate the tyres capability to stop on a wet road. This can be found this on the sidewall near the tempature grade.
- Treadwear Grades: This is a comparative rating which is produced by looking at the wear rate of the tyre, when tested, under specific conditions. It is rated fro 60 to 500 in increments of 20. The higher the rating the longer the tread should last.
ECE approval number and mark: This indicated the tyres conformity to standards which are set out by the United Nations Economic Commission for Europe (U.N.E.C.E.).
European Noise Homologation: If your tyre has a European Noise Approved number, it fully adheres with the directive 2001/43/EC. This is measured in decibals and is found online when purchasing the tyre or on the tyre packaging.
1: sound wave means the tyre is 3 dB or more below the future noise limtis.
2: sound waves means the tyre produces an average amount of noise and is equal to or 3 dB below the future noise limit
3: sound waves means the tyre is above the future noise limit, but complies as of now
Run Flat Tyres: Various tyre markings can indicate Run Flat tyres, including RFT, DSST, RunFL and ROF.
Winter Markings: M+S (Mud+Snow) indicates a snow tyre. An image of a snowflake and mountain is another symbol for snow tyres.
UTQG code: Uniform Tire Quality Grading is a U.S. standard, specified by the U.S. Department of Transportation for car tyres. It must be visible on all tyres which are sold in America, and can be found on most EU tyres.
The DOT Safety Standard Codes: This is a legal marking which is compulsory in many countries, meaning the tyres fully adhere to the safety standards imposed by the DOT.
- The tyre fully adheres to DOT safety standards
- Plant code no. and manufacturer as allocated from DOT
- Code no. for the tyre size
- Manufacturing date
How do you know when it is time to replace your tyre?
Tread Wear Indicator: TWI is vital. It is a safety feature which verifies how much tread is left on the tyre. Rubber bars are set at a height of exactly 1.6 millimetres. When the tread is worn down and reaches these bars, the tyre must be replaced. You should also be able to see the letters TWI.
The majority of EU countries have a minimum tread depth of 1.6mm; it is always worth checking this if you are planning to travel.
If you are unsure if your tyres need replacing, more information is provided at How to Know When to Repair or Replace a Tyre
By summarising the codes and markings you might come across on a tyre we hope you have found this useful and learnt more about how to better understand your tyre markings.
Check out What Size Tyre Fits My Car? for more information.