If you look closely at a car tyre, you will see a set of digits and letters on the sidewall. This code can reveal important information about the tyre and it isn’t even that difficult to decipher. If you know how to read car tyre codes, you will be able to make better decisions when it comes to buying and maintaining car tyres.
Let’s explore what the special numbers and letters on the tyres represent and how you can use this information.
Why is it Important to Learn to Read Codes on a Car Tyre
It is important to check the tyre manufacturing date for everyone looking to buy a used car in Dubai. Given the fact that everyone has to change tyres after 5 years if you are going to buy a vehicle with a 5-year-old tyre, there is a possibility that Roads and Transport Authority (RTA) may fail the vehicle registration renewal test. RTA recommends checking the manufacturing year of the tyre before fitting it in your vehicle. It is also important that you follow a car tyre buying checklist to ensure that you don’t miss a significant detail.
Here is an example of a code for your reference: 275/40/R 20 95 Y SSR MOE M+S DOT 33/17. Let’s identify the manufacturing date:
- DoT means compliance with Department of Transport’s vehicle safety standards.
- 33 is the week of manufacture.
- 17 here represents 2017, the year of manufacturing.
Read on to know what does the additional markings on a car tyre represent and when to change the car’s tyres:
How to Read The Markings On a Car Tyre
Before we grasp the meaning of car tyre codes and what they are, we need to know what each marking denotes. It is interesting to know that there are not one but six principal markings along with a seventh additional marking that we will explain later in detail.
Before we begin, we need to conceive a model sequence as a reference. Imagine we are looking at one of the codes, i.e., 275/40/R 20 95 Y.
Now, let’s decipher each part of this code.
Width of the Tyre
It is vital to know the dimensions of your vehicle’s tyres. The tyre’s width is mentioned as the first three digits of the sequence. In the given code, the tyre is 275 mm wide from one sidewall to the other.
The Aspect Ratio
The aspect ratio denoting the height might be a bit complex for some to comprehend. The next two numb i.e. 40 in the given code represent the aspect ratio. It is the height-to-width ratio of the tyre, calculated in percentage. It implies the tyre’s height that runs outward from the rim, calculated as the percentage of the width.
In the given example, the height of the tyre is 40% of its width. To calculate the height of this tyre: 275mm x 40% = 110 mm. It is different from the Rim diameter, which is a measure of how wide the tyre is at the centre from one bead seat area to another.
The Construction
The next marking is a letter instead of a number. It denotes the type of construction of the tyre. For the given model, the ‘R’ implies Radial Construction. The other types of construction are ‘B’ for Bias-ply, or Diagonal construction denoted by a ‘D’.
The radial construction is the most common nowadays. It indicates that the inner steel belt or ply cords are configured at right angles to the direction of the wheel rotation. The internal cords run from one bead seat area to the opposite end, and their orientation defines this letter in the sequence.
The Diameter of the Rim
In the given sequence ‘275/40/R 20 95 Y‘, the rim diameter is ’20’ in inches.
Load Index
Next is the load index or the load capacity of the wheel, which is ’95’ in 275/40/R 20 95 Y. Load index is the load handling capacity of the tyre. For example, a load index of 95 has a different load limit than another tyre with a load index of 99, at ideal tyre inflation and speed. You must check the load index of your vehicle wheels before buying a new tyre as you cannot replace your tyre with a lower load index. It should be the same as others or of a higher value.
Each numerical value of load index has a specific load capacity, here load index 95 refers to a capacity of 690 kg.
The Speed Rating
The other letter of the tyre code indicates the speed rating of the tyre – i.e. ‘Y’ in the given sequence. This is the last principal marking on the tyre, after which comes the additional sequence.
The speed rating is another important factor behind tyres performance. It is a measure of the maximum permissible speed that the tyre can withstand at the full load capacity. It is denoted by a letter in the sequence, where each letter refers to a different speed capacity operative by the vehicle. In our example, ‘Y’ represents a speed rating of up to 300 km/h.
Additional Markings
There are some other codes on tyres as well after the speed rating symbol. These include information such as the tyre age code, compliance with the safety standards of the Department of Transport (DOT) and more.
Here is an example: 275/40/R 20 95 Y SSR MOE M+S DOT 33/17. Let’s decode the additional codes in this sequence:
- The code SSR stands for Self-Supporting Run flat tyre.
- The M in MOE here stands for Mercedes and OE denotes the factory fitted original parts. Overall, the code represents that tyres are manufactured as per the brand’s specification and model type.
- M+S denotes that the tyre is suitable to be driven in mud and snow.
- DOT means compliance with Department for Transport vehicle’s safety standards.
- 33 is the week of manufacture.
- 17 here represents 2017, the year of manufacturing.
Things to Consider
When buying a tyre in the UAE, ensure that its manufacturing date is not more than 150 days old. It is advised by Roads and Transport Authority (RTA) and professional mechanics as well. If you fit old and used tyres, then your vehicle may fail the vehicle registration renewal test given the wear and tear on the tyre that is not suitable for the Dubai roads. Since now you know how to read car tyre markings, you can easily identify the manufacturing year.
Now that you know how to read car tyre codes, you can interpret the information embedded on the tyres to optimize your selection and purchase the best for your vehicle. If buying a new tyre does not fit your budget, you may opt to buy a second-hand tyre in the UAE for your vehicle. Since there are many pros and cons of buying used car tyres, you may decide what’s best for your car accordingly.
Stay tuned to the top auto blog in the UAE for more information on car parts and accessories.
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