As an approved expert HA-012, our test certificates are valid for applying a type approval for studs and studded tires from the Finnish Transport Safety Agency, TRAFI.
Studs that are used in studded tires must be type approved. A tire must not have > 50 studs per 1 meter of rolling circumference and the mean protrusion must not exceed 1,2 mm. Studs may also be granted type approval according to a test that reliably measures the road wear caused by studs. When using this method, the tested stud type approval is only valid when using studs in accordance with the tire, number of studs and stud installation conditions related to the type approval.
The overrun test was developed to determine the road wear caused by studded winter tires. Specially manufactured stone samples are weighted precisely before and after the overrun, the weight loss describing the road wear in grams.
In order to get a type approval for a tire and stud combination, the road wear must be below a limit value defined by The Finnish Transport Safety Agency, Trafi. If the type approval is granted based on an overrun test certificate, there are no other restrictions for the stud configuration.
Trafi has set parameters and limit values for different load categories, as well as requirements for the studding quality. Additionally, the stud protrusion change during the test is restricted. A summary of test parameters and limit values can be found in Traficom website.