Question

we observe that the wheels of buses and trucks are heavier why?

Answer 1

Tyres are required to transfer the weight of the vehicle to the road surface in a grippy yet non damaging way. The tyre size is decided based on the unladden and max laden weight the vehicle is designed for. As the weight increases, the amount of pressurised air required to lift that weight increases. Propotionately, the amount of rubber required to hold that pressurised air increases. Thus with the increase in the amount of the rubber, the overall weight of tge tyre increases.