Avon Roadrider Rear tyre 150/70/V18
Correct tyre sizes for A1-A6 machines are

120/80/V16 Front, and 130/80/V18 Rear.

Correct tyre sizes for A7-A8 machines are 120/70/ZR17 and 150/70/ZR18 Rear.

It is illegal to mix:-
Bias belted front with Crossply rear
Radial front with Crossply rear
Radial Front with Bias belted rear