Team AckoMay 15, 2023
Tyres are one of the most crucial components of a vehicle, providing the necessary grip and control to ensure safety on the road.
However, choosing the wrong tyre size can compromise the driving experience, affecting your vehicle's performance and fuel efficiency and causing potential safety hazards.
In this article, we will explore the different aspects of tyre size, including how to read tyre size markings, factors to consider when choosing a tyre size, and the potential consequences of using incorrect tyre sizes.
So, whether you are a seasoned driver or a first-time car owner, read on to discover everything you need to know about tyre sizes.
Your car's tyre size refers to the tyre's dimensions.
It includes the width, aspect ratio and the diameter of a tyre.
This information is combined and written as tyre size on the tyre's sidewall using specific numbers and letters.
Car tyre specification contains many criteria, such as load index rating, speed symbol rating, and tyre size.
Tyre specification changes according to the make and model of the car.
Tyre size is measured using a standard system known as the "Metric System".
The numbers written on the tyre's sidewall representing the tyre's width, aspect ratio, and diameter are given in millimetres.
The letter 'R' stands for "Radial Construction", the most common type of tyre construction used nowadays.
The tyre size chart describes the size and specifications of a tyre.
It contains numbers and letters, each of which represents a different value.
Let's take the example of P205/55R16 91V to understand each number and letter.
The letter "P" indicates that the tyre is designed for passenger vehicles. It is suitable for cars, vans, and SUVs.
The number "205" is the tyre's width in millimetres.This number indicates the width of the tyre from one sidewall to another.
The number "55" is the aspect ratio of the tyre. It represents the height of the sidewall as a percentage of the tyre's width. In this instance, the sidewall height is 55% of the tyre's width.
The letter "R" stands for radial construction, a type of tyre construction most commonly used nowadays.
The number "16" is the diameter of the wheel in inches.
The number "91" is the load index. The load index indicates the maximum weight a tyre can support when inflated to its recommended car tyre pressure. It would help if you referred to a load index chart to determine the maximum weight a tyre can support based on its load index. For instance, a tyre with a load index of 91 can support up to 615 kilograms (1356 pounds) of weight.
Finally, the "V" is the speed symbol rating, indicating the maximum speed a tyre can handle safely. In this example, the tyre is designed to handle a speed of up to 240 kilometres per hour (149 miles per hour).
A tyre's aspect ratio is how tall the tire's sidewall is compared to its width, shown as a percentage.
For example, if a tyre’s aspect ratio is 55, the height of the sidewall is 55% of the tyre's width.
A lower aspect ratio means the tyre has a wider tread and a shorter sidewall. It improves the tyre's handling.
However, it makes the ride feel harsher because there is less cushioning from the sidewall.
While a higher aspect ratio means the tyre has a taller sidewall and a narrower tread. It can result in a more comfortable ride.
Moreover, it provides better traction on rough roads because the taller sidewall can absorb more of the bumps and imperfections in the road.
Consider these scenarios - better handling and performance or a more comfortable ride with better traction on rough roads, and choose according to your preference.
The tyre's overall diameter is the main criterion in choosing the right tyre specification for your vehicle. It is the distance from the ground to the top of the tyre.
If the overall diameter of the new tyre is different from the original tyre, it can affect the speedometer accuracy, fuel economy, and handling the car becomes troublesome.
For example, installing a larger tyre than the original one will cover more distance in one revolution.
Hence, the speedometer will show a slower speed than your driving. It can be dangerous and can result in a fine for speeding.
Similarly, if you install a smaller tyre than the original one, the speedometer will show a faster speed than you are driving. It affects the car's fuel economy and handling.
So, to compare different tyre sizes accurately, it's recommended to use a tyre size calculator.
This tool will help you determine the overall diameter of the new tyre and compare it with the original tyre.
You may come across many types of tyres.
However, choosing the correct tyre size is crucial for your safety and the performance of your car.
Here are some reasons why choosing the right tyre size is important.
Safety implications of choosing the wrong tyre size:
Driving with the wrong tyre size can be dangerous.
For instance, choosing a weak tyre that cannot support the weight of your car and passengers might burst the tyre, sometimes leading to a fatal situation on the road.
Similarly, choosing a too-big tyre for your vehicle makes it less stable and increases the chances of rolling over.
Therefore, choosing the right tyre size for your car is vital to avoid any safety issues.
Effects on car performance, handling, and fuel efficiency:
The right tyre size affects your car's performance, handling, and fuel efficiency.
For example, installing a wider tyre with a lower aspect ratio improves your car's handling and performance, but it can also result in a harsher ride and lower fuel efficiency.
Likewise, if you install a narrower tyre with a higher aspect ratio, it provides a more comfortable ride, but it may also reduce the handling and performance of your car.
Keep these factors in mind while choosing the tyre size for your car.
Type of the car: For example, a small hatchback requires smaller and narrower tyres. Whereas SUVs need bigger and wider tyres to support their weight and provide better traction.
Types of tyres: For example, all-season and summer tyres are commonly available in various sizes to fit multiple cars like SUVs and even light trucks. However, winter tyres are often available in narrower sizes to provide a better grip on snowy and icy roads. Performance tyres are often available in larger sizes to fit sports cars and other high-performance vehicles. Similarly, off-road tyres are available in larger sizes with deeper treads for better traction on rough terrains.
Type of driving: Refers to the driving conditions you typically encounter. For example, if you primarily drive on highways, prioritise fuel efficiency and a comfortable ride. On the other hand, if you often drive on rough, unpaved roads, you might prioritise durability and traction.
Weather conditions: For example, you need tyres with good wet or snow traction if you live in an area more prone to rain or snow. On the other hand, if you live in a hot and dry place, you may want tyres that are better suited for high temperatures and dry road conditions.
Budget: Consider your budget before buying the tyres. Choose the right tyre size for your car which doesn’t empty your pockets!
A tyre size calculator is a tool that helps you choose the right tyre size for your car. It can compare different tyre sizes and tell you the overall diameter of the new tyre.
It is essential because installing a tyre with a different diameter can affect your car's speedometer accuracy, fuel economy, and handling.
Using a tyre size calculator, you can ensure the new tyre is compatible with your vehicle and avoid any safety or performance issues.
The easiest way to determine the correct tyre size for your car is to consult the owner's manual and the tyre placard. It is placed on the side of the driver's door. The recommended tyre size will be listed there.
It's not recommended to use a different size tyre on your car than what is recommended by the manufacturer. It will affect the handling, performance, and safety of your vehicle. Always choose a tyre size recommended for your car's specific model.
The load index indicates the maximum weight a tyre can support. The speed rating indicates the top speed that a tyre can safely handle. Both factors are essential when choosing the right tyre size for your car.
Choosing a wide tyre for your car can increase rolling resistance, resulting in lower fuel efficiency. On the other hand, choosing a narrow tyre for your vehicle can increase aerodynamic drag, which also decreases fuel efficiency.
A tyre size calculator is an excellent tool for comparing different tyre sizes accurately. This tool will help you determine the overall diameter of the new tyre and will ensure compatibility with your car.
Disclaimer: The content on this page is generic and shared only for informational and explanatory purposes. It is based on industry experience and several secondary sources on the internet, and is subject to changes. Please go through the applicable policy wordings for updated ACKO-centric content, and before making any insurance-related decisions.
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