2-valve conversions: Which tyres fit and what can I ride

Tyres play a decisive role in conversions. However, I do not want to go into the evaluation of the individual tyre types and makes here. As a rule, the reason for fitting scrambler tyres is not that people want to go off-road. It should be clear to everyone that a low-profile sports tyre will always perform better than a 4.50 Shinko bias-ply tyre or a TKC80 scrambler tyre.
 
For tyre conversions, especially when changing the size, there are usually no expert opinions or clearance certificates from BMW or the tyre companies. The TÜV is required to check the suitability of the tyres for the respective motorbike. Registration is then carried out by individual acceptance. Fortunately, there are many TÜV test engineers who have a great affinity for motorbikes and have the corresponding competence to evaluate such a conversion and also to approve it. You need such an inspector! 
Unfortunately, there are also examiners who do not want to take on this responsibility and do not want to make any entries without an expert opinion or a clearance certificate. If the vehicle is a 300km/h fast S1000RR, I can still muster some understanding. But not with our beloved BMW 2-valves, which are miles away from such speed ranges. Should you come to such a test engineer, I would recommend you to break off and go to another TÜV office.
But even if you get to a competent inspector, there are rules you have to follow. 
  1. The tyre size must match the rim size. As a rule, tyre manufacturers indicate in their technical tables which rim dimensions are required for the tyre in question. 
  2. The speed index of the tyres must be at least 10 km/h higher than the maximum speed stated in the papers.
  3. An exception applies to M&S tyres. These winter tyres are approved for a maximum speed of 160 km/h and may also be fitted to vehicles whose registered maximum speed is higher. A marking, "Max. 160km/h" must be affixed to the speedometer (sticker).   
  4. The clearance of the tyres must be guaranteed. Here we assume a minimum distance of 5mm from vehicle components to the side of the tyre. Longitudinally, it must be noted that the tyre grows at higher speeds. Here we ensure a minimum distance of 10mm. 
Here is a list of tyre combinations that we use on our SE Concept Bikes. As I said, we install these tyres and then have the complete vehicles approved by our TÜV test centre. However, this list is no guarantee that your local TÜV office will behave in the same way. So it's better to check with them before fitting.
  
BMW Paralever R80R R100R models 1991-1996:
Tyre size original: front 110/80-18 and 140/80 - 17
Possible scrambler tyres:
front 110/80-18, rear 140/80-17
Bridgestone BT 41 M&S
Continetal TKC 80 M&S
Continetal TKC70 M&S
Heidenau K60 M&S
Michelin Anakee M&S
Pirelli MT90 up to 180km/h
Possible road tyres:
front 110/80-18, rear 140/80-17
Bridgestone BT45
Bridgestone BT46
Continental ContiGo
Metzeler Lasertec

BMW Monolever R80/100 models 1984-1995:
Tyre size original: front 90/90-18 and rear 120/90-18

Possible scrambler tyres:
front 110/80-18, rear 140/80-18
Continetal TKC 80 M&S
Heidenau K 60 M&S
Michelin Anakee M&S
Pirelli MT 90 up to 180km/h

Possible road tyres:
front 110/80-18, rear 130/80-18
Bridgestone BT46
Continental ContiGo
Metzeler Lasertec
Michelin Road Classic
Pirelli Sport Demon


alternativ Diagonalreifen:
vorne
Shinko E270      4.00-18
Shinko E-270     4.50-18
hinten:
Shinko E270      4.00-18
Shinko E-270     4.50-18

  

BMW Twinshock R80/100 models 1980-1984:
Tyre size original: front 3.25-19 and rear 4.00-18

Possible scrambler tyres:
front 110/80-19, rear 120/90-18
Continetal TKC 80 M&S
Heidenau K 60 M&S
Bridgestone AX 41 M&S

Possible road tyres:
front 100/90-18, rear 120/90-18
Bridgestone BT46
Continental ContiGo
Michelin Road Classic
Pirelli Sport Demon


alternativ Diagonalreifen:
vorne
Shinko E270      4.00-19
hinten:
Shinko E270      4.00-18