When selecting or replacing tyres, understanding the key dimensions is essential. Here’s a breakdown of the main terms you’ll encounter:

Width:
This refers to the tyre’s section width in millimetres, measured from the inner sidewall to the outer sidewall.
Example: 195mm

Aspect Ratio:
This is the tyre’s sidewall height expressed as a percentage of its width. A lower aspect ratio means a lower profile tyre.
Example: An aspect ratio of 65 means the sidewall height is 65% of the tyre’s width.

Tyre Construction:
Indicates how the tyre is built. Most modern passenger tyres use radial construction, denoted by the letter “R”.
Example: R (Radial)

Rim Diameter:
The size of the wheel rim in inches that the tyre fits onto. This is crucial when matching tyres to wheels.
Example: 15 inches

Load Index & Speed Rating:
These indicate the maximum weight a tyre can carry and the top speed it can handle—assuming it’s properly inflated and in good condition.
Example: 91V – where 91 is the load index and V is the speed rating

Tip: Load and Speed Ratings can be found on manufacturer websites!