Which vehicle modifications must be approved (tuning)?

Under Art. 34 para. 2 VTS, the keeper must report modifications to vehicles without delay; modified vehicles must be re-inspected (“modification inspection”). Only after a successful inspection may the modified vehicle continue to be used.

• Changes to the vehicle classification (kind/class).
• Changes to the weights, dimensions, wheelbase and track width.
• Interventions that change exhaust or noise emissions — proof that the rules in force at the first entry into circulation are met.
• Exhaust systems not approved for the vehicle type.
• Changes to the power transmission (gearbox / axle ratio).
• Wheels not approved for the vehicle type (exception M1/N1: offset (ET) deviation up to 5 mm).

Unreported or unapproved modifications can mean a vehicle is no longer compliant and thus no longer in a safe operating condition — with consequences at a check, an inspection and with the insurer.