Those, who want to equip their car with tyres not listed in the vehicle license, do not always have to register the tyres separately.
Information in the vehicle documents
A vehicle licence – from October 2005 correctly referred to as Part I of the vehicle registration certificate – contains an indication of the tyres authorised for that particular vehicle. One can find detailed information about sizes of tyres in the Articles 15.1, 15.2 and 15.3. - The information stands for every axis respectively. Changes regarding tyres are also noted in the Article 22. There are more sizes to choose in older vehicle licenses. You can still use those papers. However, the specification of a single tyre size in the new vehicle registration certificates does not mean that only this particular tyre size is allowed.
Find more permitted tyres
Other allowed sizes can be found in the EEC or EC Certificate of Conformity, also known as CoC paper (Certificate of Conformity). Since 2005, car producers have to hand over this listing when selling a new car. It contains all kinds of technical data on the vehicle, including Articles 32 and 50 with the information on all approved tyre sizes. If you do not have or lose your CoC paper, you can request it from the car manufacturer for a fee. Many manufacturers have also put corresponding databases with search function online. If the tyre is not mentioned in the vehicle registration certificate but can be found in the CoC papers, it can be mounted without thinking twice. As evidence for the police and especially the Technical Inspection Association, a copy of the CoC paper should always be carried along. The tyre size can also be mentioned in Part I of the vehicle registration certificate afterwards, then it is unnecessary to carry the CoC paper along. This addition is not mandatory, though.
Individual report or individual approval
If the tyres are not mentioned in the vehicle registration certificate or the CoC papers, then an expert must prepare an opinion on the roadworthiness of the tyre. Such an "exceptional statement of facts" mentioned in Part I, Article 22 of the vehicle registration certificate, is always chargeable. The expert checks the suitability of the tyre and the mountability on the rim – this requires the tyre manufacturer to provide a certificate. If everything is all right, the expert will issue the report commonly known as General Operating License. The change will then be entered in Part I, Article 22 of the vehicle registration certificate, as an ABE template, and is, therefore, official.
Driving with unauthorised tyres
Driving with unauthorised tyres is of course not allowed and can also be very costly. If only one part of the car is not officially approved – even if it is just a tyre – the approval for the entyre vehicle is immediately cancelled. You can't drive without an operating license – the police can ensure it. You can also lose your insurance coverage under such circumstances.