Tyre Size Decoded: What All Those Numbers Mean 

Have you ever wondered about the readings that are engraved on a tyre’s sidewall? For instance, 195/55 R16 87V, which is the Maruti Suzuki Baleno’s top-most variant’s tyre profile. As you can see, it consists of three numbers only, followed by a character (87V, for example) on the extreme right.

The purpose of this reading is to indicate the width and height of the rubber as well as the size of the rim. In addition, it indicates the maximum speed at which you are allowed to drive. If driven beyond the threshold, the wear and tear will happen at a fast rate.

Decoding the Tyre Size

Let’s take the above-mentioned example, which is 195/55 R16 87V. The ‘195,’ which is measured in millimetres shows the width, while ‘55’ shows the aspect ratio (the size of the sidewall). The ‘R’ followed by a number indicates the size of the rim. Technically, it stands for radial construction. The last one, the ’87,’ indicates the load capacity of the tyre, and the ‘V’ letter following the ‘87’ number stands for the speed symbol (also called speed rating) that indicates the maximum speed for the tyre at the full load.

What is the aspect ratio? The aspect ratio is the height of the sidewall or the distance between the rim and the tip of the rubber. It is converted from ratio to percentage, making the above-mentioned tyre profile have a 55% aspect ratio.

As for speed rating, the higher the letter, the faster the vehicle will be able to travel safely.

The Tyre Types

• Categories Tyres: This type of tyre is widely used among standard vehicles. The thread of these tyres consists of symmetrical patterns throughout. But, at the same time, some high-octane performance cars use tyres with unique tread patterns.

• Asymmetric Tyres: Tyres of this type comprise different tread patterns on the outer and inner edges of the tread for better performance. The outside edge of the tyre consists of a large tread block that helps with cornering, while the inside edge of the tyre has a small tread block that is designed to provide grip in wet road conditions. It is also worth mentioning that the words ‘outside’ and ‘inside’ written on the tyre’s sidewall indicate which side the tyre should be mounted on.

• Directional Tyres: As the name might hint, the directional tyres are designed to rotate in one direction only. That said, you will find an arrow on the tyre sidewall that indicates the direction. As far as its usability is concerned, these Directional tyres are useful in dispersing the water, especially when it gets accumulated in front of the tyre. It also benefits in decreasing road noise and improving directional stability.

• All-Season Tyres: In most countries, these tyres are widely used in all vehicles. But, people living in countries with extreme winters keep a separate set of winter tyres. In parallel, some people also buy a separate set of summer tyres. However, for convenience, the tyre manufacturers introduced the All-Season tyres. It can withstand any temperature, be it heat or cold. The All-Season tyres incorporate high silica composition which is suited for low temperatures and a tread pattern that is similar to both summer and winter tyres. It is a preferred choice over the specialised tyres, as it avoids the cost of swapping wheels and tyres as well as other hassles.

• Winter Tyres: These tyres are also known as mud and snow (M+S or M&S) tyres. The tread patterns on these tyres are specialised in offering traction on ice and snow surfaces. They are, of course, much better than the summer tyres. For your reference, the rubber in normal tyres starts to harden, especially at temperatures below 7 degrees Celsius, as a result, it loses grip on wet, cold, snow, and ice surfaces. On the contrary, the winter tyres remain soft and flexible at low temperatures and maintain grip thanks to special grooves in the tread, known as Sips. The Sips offer superior traction, handling as well as braking in winter driving conditions.

Note: A typical summer-oriented tyre consists of approximately 200 sips, while a winter tyre consists of approximately 1500 sips.

• High-Speed Tyres: As the name suggests, these tyres are designed for high-performance vehicles. The materials and the way they are designed are more durable than standard tyres, as they can withstand high-speed rolling resistance and other areas as well, such as high temperatures and strong G-Force under hard cornering.

Below is the chart of commonly available tyre speed ratings in India:

• Run-Flat Tyres: You may have probably come across these tyres. It is also known as RFT. In India, only a few luxury vehicles are equipped with this. Brands like Lexus, BMW, Audi, etc., offer run-flat tyres in their vehicles. The USP of these tyres includes an unconventional design that allows the tyre to run safely for a good number of kilometres with a maximum speed limit of 80 km/h (as per the manufacturers’ recommendation).

A run-flat tyre has a supporting structure that is fixed to the rim that can be found inside the pneumatic tyre, due to which, it can bear the load when tyres deflate.

While having pros, there are also cons. Most of the RFTs cannot be repaired when punctured, but some of them are repairable, as well. That depends on the brand and model of the tyre. In addition, RFTs are also known for being noisy sometimes on bumps.

The Final Words

So, these were a few types of popular tyres that are suitable for certain topographies and climates or all. That said, they all are meant for different purposes as well as for different vehicles and have different prices. Before replacing OEM tyres, it’s always best to ask an expert about the best suitable after-market tyre, so that it doesn’t hamper the true capability and ride quality of the concerned vehicle.

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