Questions of Technical Alterations to vehicles already registered
In such cases, your local registration authority is responsible and should be consulted, as technical modifications can cause the approval to lapse.
Alterations to vehicles which are already on the road and which are not covered by an approval (National Type Approval, test reports for parts)!
Subsequent technical modifications to a vehicle can lead to the type approval becoming invalid. This is always the case if the modification endangers road safety or the environment or if the vehicle class is changed.
According to the Road licensing Regulations (StVZO), the local registration authority decides in individual cases whether a vehicle's type approval has become invalid due to the modification. For this decision the local authority can, at the vehicle holder's expense, obtain an expert's test report.
Avoid unnecessary trouble and expense: talk to an expert before modifying your vehicle.
i.a. § 19 StVZO "Issuing and Validity of Type Approvals" and the "Catalogue of examples of modifications to vehicles and their effect on vehicles' type approvals" published in the Verkehrsblatt *), 1999, page 451.
Further information and practical explanations are contained in a book published by the Kirschbaum Verlag under the title "§ 19 StVZO - Änderung am Fahrzeug und Betriebserlaubnis" (Vehicle Modifications and type approvals) 2nd edition, which is can be found in specialist libraries.
*) official information sheet of the Federal Ministry of Transport, Building and Urban Affairs, published by Verkehrsblatt-Verlag, Hohe Straße 39, 44139 Dortmund, Verkehrsblatt-Verlag