The aspect ratio, also known as the profile or series, is a critical component of your tyre’s size designation. It’s expressed as a percentage and represents the relationship between the tyre’s sidewall height and its width.
To calculate the sidewall height, simply multiply the tyre’s width by the aspect ratio percentage. For example, if your tyre size is 225/55R16, the aspect ratio is 55%. This means the sidewall height is 55% of the tyre’s width, which is 225 millimetres.
In this case, the sidewall height would be: 225 mm × 0.55 = 123.75 mm (or about 4.9 inches)
The aspect ratio plays a significant role in your vehicle’s performance and ride quality. A lower aspect ratio (e.g., 45%) results in a shorter sidewall, which provides better handling and steering response but may lead to a firmer ride. A higher aspect ratio (e.g., 65%) means a taller sidewall, which offers a smoother ride and better absorption of road imperfections but may slightly diminish handling performance.
When replacing your tyres, it’s essential to maintain the same aspect ratio as recommended by your vehicle manufacturer to ensure optimal performance, safety, and comfort.