Due to historical reasons, China's early tire production technology was introduced to the British standard, the production of bias 

tires, and even the later steel wire radial tires, all use the 

British specifications. In the era of tubeless tires for trucks, tires still use British specifications.

In Europe, most countries use metric tires, and most imported cars are equipped with metric tires.

British gauge tires

12R22.5 is the imperial specification of the tire, which means that the cross section width of the tire is 12 inches (30.47 cm) meters. 

The rim diameter is 22.5 inches (57.1 cm).British tire specifications can only provide tire cross-section width, tire type, mounting 

rim size information.

Compared to the imperial specification, the metric tire specification can provide more information about the tire, such as the tire 

break section width, flat ratio, mounting rim size, and we can also calculate the tire break section height from the flat ratio.

Metric tires

295/80R22.5 is the metric tire specification, its specific meaning is the tire break section width 29.5 cm, 80 is the flat ratio of the tire. 

The tire is mounted on a rim diameter of 22.5 inches (57.1 cm).

The flat ratio is also called the height to width ratio, and the flat ratio is calculated by dividing the height of the broken section of the 

tire by the width of the broken section of the tire. At present, the common tire flat ratio in China is 80, in addition to 80, 70, 60,

At present, the minimum known civilian truck tire flat ratio is 45.