ISO 9112:2008 specifies two methods for measuring the rolling circumference and the number of revolutions per unit distance (kilometre) of new commercial vehicle tyres, under loaded conditions, for use on trucks and buses.
The first method is a drum method consisting of loading a test tyre mounted on a free axle against a driven road wheel (or drum) of specified diameter. The second method involves a vehicle whose drive axle is equipped with the test tyres driven on a straight, paved road. The values thus obtained are not intended for use as levels of performance or quality.
ISO 9112:2008 applies to all truck and bus tyres.