What is Aspect Ratio in Tyre, How to Measure and Calculate?

The sidewalls of your vehicle’s tyres contain essential information regarding the tyre size. Noting these numbers becomes exceptionally crucial when you purchase a new set of tyres.

Among these numbers is the tyre aspect ratio, depicted by a percentage. It indicates the total height of a tyre.

The following sections detail tyre aspect ratios, their calculation, and much more.

The height of the tyre from the bead to the tread expressed as a percentage is referred to as the aspect ratio of a tyre. For instance, if the aspect ratio is 45, the height of the sidewall of a tyre is equal to 45% of its width.

The tyre aspect ratio has much to do with any vehicle’s overall driving efficiency. Take a look at the pointers below to understand how:

• The more the aspect ratio, the taller the tyre’s sidewall. Heavy vehicles, including buses, lorries, and luxury cars, use tyres with aspect ratios as high as around 95. High aspect ratio tyres may decrease handling yet offer more comfort when driving through bumpy roads.
• On the other hand, performance or sports cars come with low aspect ratio tyres. This means that they are equipped with tyres that have stiffer walls, allowing better cornering capacity. However, note that the vehicles with low aspect ratio tyres may fail to deliver optimal drive comfort when driving on bumpy surfaces.
• Regarding passenger vehicles that are equipped with regular tyres, they come with a healthy balance of low and high tyre aspect ratios to offer optimal driving comfort and precision.

Calculating the tyre aspect ratio is simple. The aspect ratio is typically depicted after the section width in the tyre’s sidewall. It is usually a two-digit number. For instance, if the number is 65, it would indicate that the height of your car’s tyre equals 65% of its width.

Thus, you can calculate the aspect ratio of a tyre through this formula:

 Aspect Ratio (%) = H (Section Height of Tyre) / W (Section Width of Tyre) X 100

Apart from the aspect ratio, the tyre size code also provides other vital details.

Let’s understand with an example. Suppose the sidewall of your car tyre has the following numbers - 205 / 60 R16 92 H, it would mean:

• 205: Section width of the tyre in millimetres.
• 60: Aspect ratio.
• R: Radial construction.
• 16: The measurement of the rim in inches.
• 92: The maximum load capacity of the tyre, or the load index.
• H: Highest permissible speed of the tyre or the speed symbol.

Thus, it is highly crucial that you purchase a tyre with the needed tyre aspect ratio. Consider noting these numbers and talk to the servicemen when you are buying a new set of tyres for an informed decision. It will have a significant impact on your driving comfort and safety.