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Tyre Size Explained – Learn How to Read Your Tyre Parameters

Whether you are looking to purchase new tyres or planning to replace the existing ones, having the tyre size explained to you is crucial. But why is that so? The reason is only the car tyres with the right size (you can find the size on the sidewall) and quality can ensure your safety on the road. Since they are the only contact between your vehicle and the road, you cannot just pick any tyre type from the shelf and use it. 
 
The ability to support the weight of the vehicle, absorb vibrations from the road, and offering grip for acceleration and braking is what makes tyres such a vital component of your vehicle. Not having the right tyres and overlooking its condition may endanger your safety. 
 
The question is, how do you read all that information on the sidewall of a tyre? Understanding it is the key to purchase the best car tyres. It is what I will be covering in this blog (vlog) today. Let’s go over all the characters you find in a tyre’s sidewall, and I will help interpret the meaning of each of them.

How to read your tyre size explained?

Once you have your tyre size explained, it is quite easy to understand. Regardless of whether you have new or part worn tyres, their sidewall has a set of measurement printed onto it. A combination of letters and numbers form these codes.  
 
For understanding, assume that you find the following information on the sidewall of your tyre: 
205/65 R15 94H 
Let’s have a look at the individual set of numerals and see what they mean.
Tyre size explained - tyre parameters
 
Tyre Width
Finding tyre width is the first component when it comes to having your tyre size explained. The first three numbers at the beginning of the size refer to the width of the rubber. The width represents the distance from one sidewall of the tyre to the other in millimetres. In our example, the tyre width is 205 millimetres. 
 
Tyre Aspect Ratio
Understanding the next two numbers right after the slash is the next step to have the tyre size explained. These numbers refer to the aspect ratio, which is the ratio of the height of the tyre’s sidewalls to its width. The height of a tyre’s sidewall is positively related to its aspect ratio. The aspect ratio in our example is 65. It means the size of tyre’s sidewall is equal to 65 per cent of the tyre’s width. 
 
Tyre Construction
The first letter after the aspect ratio tells us about the construction or the variety of the tyre. The tyre types include diagonal (D), bias belt (B), radial (R), and others. Let’s take a look at this letter in our example, and we can see that ‘R’ denotes the tyre construction. It means it has a radial construction and the layers follow a radial pattern across the tyre. 
 
Tyre Diameter
The numbers after tyre construction refer to the diameter of the tyre stated in inches. To have the tyre size explained simply, it is the size of the tyre from one end to the other. The numbers after the letter R in our example are ‘15’, telling the diameter of the tyre is 15 inches. 
 
Tyre diameter is relatively crucial to note out of other details because it shows the rim over which the tyre would fit. Let’s say your rim is 12 inches, and your tyre has a diameter of 16. In this case, the tyre is not appropriate for the rim.  
Tyre size explained - Width, Aspect Ratio, Rim Diameter
Tyre Load Index
Let’s move on to the next, and the final numbers in our tyre size explained guide. These numbers are a code that tells you of the maximum load your tyres can handle. However, to decrypt this code into weight denominated in kilograms, you will have to consult the tyre load index ratings. Let’s quickly go over this tyre load rating illustrated below. 
Load Index 81 82 85 86 87 88 90 92 94 96
Max Load (Kg) 462 475 515 530 545 560 600 630 670 710
To have the tyre size explained, let’s refer to our example. It shows us the tyre has a load index of ‘94’. After referring to the load index ratings, we know that our tyre can support a weight of up to 670 kg.
  
Speed Rating
The letter at the end of the size informs us of the maximum speed the tyre can handle after we fit it correctly by filling the recommended air pressure. But same as the load index, you must decipher this symbol into speed stated in kilometers per hour by using the car tyre speed symbol ratings. Let’s have a look at this tyre speed rating below.
Speed Symbol N P Q R S T H V W Y
Max Speed (km/h) 140 150 160 170 180 190 210 240 270 300
 
You can see that we have the letter ‘H’ at the end of the size in our example. By looking at the speed symbol ratings, we know that the maximum speed our tyre can hit while operating safely is 210 km/h. You would want to choose a tyre whose speed rating equals the maximum speed of your vehicle.
 
Other Tyre Markings
In addition to what we have discussed above, a tyre may also contain other markings. To have the tyre size explained, you must be familiar with these codes as well. The most common of these is a DOT code, which translates into compliance with the requirements of the U.S department of transportation. This code comprises letters and numbers, just like the information we have discussed above. 
See the following DOT code in the picture above. 
The tyre’s manufacturing date is a piece of valuable information in this code, which is visible in the last four digits. In our example, the 52nd week of 2010 is the date of its production.  
Conclusion
In the list of all those components of a vehicle that are essential for your safety, tyres hold a notable value. Having the wrong type of tyres may compromise your safety and result in losing control of your vehicle or worse. But choosing the optimal tyre for your car might be tricky if you do not know the series of codes on the sidewall. 
Each number and letter on the sidewall has a meaning to it. It makes having the tyre size explained to you essential. I hope by reading our guide, you would be on the same page with me and interpret each of those characters with ease. Not only does this information will help you get to know your tyre better, but it will also assist you in purchasing in the future.