What is aspect ratio on a tyre?
Analysing tyre aspect ratio
The aspect ratio is an important number in tyre size and will affect the way a car rides and handles.
Analysis
The aspect ratio is the second number in the tyre size. It shows the height of the sidewall of the tyre as a percentage of the width of the tyre. For example, in 205/55 R16, the aspect ratio is 55. This means that the sidewall height is 55 percent of the 205mm width, which is 113 mm.
Effect on the drive
| Lower aspect ratio (e.g. 35 or 40) | Higher aspect ratio (e.g. 60 or 65) |
|---|
| Shorter, stiffer sidewall |
Taller, more flexible sidewall |
| Sharper steering response |
More cushioned and comfortable ride |
| Better cornering grip and precision |
Better absorption of potholes and bumps |
| Firmer ride quality |
Softer ride quality |
| More vulnerable to pothole damage |
Better protection for alloy wheels |
What is a good ratio?
In general, keep the aspect ratio for your vehicle. If your vehicle offers multiple wheel sizes, a higher diameter wheel will have a lower aspect ratio. Comfort is the biggest gain when the aspect ratio is higher. Within reasonable limits, put safety for you and your passengers first and stay within the sizes approved by the manufacturer.
