Where are you not allowed to use retread tyres on 100 km/h buses?

When it comes to retread tyres on buses that travel at speeds of 100 km/h, German traffic regulations prohibit the use of these tyres on the front axle due to safety concerns. The front axle is critical for steering and handling, and using retreads in this position can compromise the bus's stability and control.

Moreover, the regulations also restrict the use of retread tyres on the rear axle for certain bus configurations. This is to ensure that all axles have optimal reliability and performance, particularly in high-speed scenarios. Therefore, the correct answer encompasses those restrictions related to both the front and rear axles.

Understanding these rules is essential for maintaining safety on the road, ensuring that buses are equipped with tyres that provide adequate traction and performance under various conditions.