Question

Why do the load carrying heavy vehicles have large number of wheels
​

Answer 1

The load carrying heavy vehicles have large numbers of wheels because ensures that the force due to load is shared among the wheels and no tyre is under pressure.

Answer 2

Explanation:

load carrying heavy vehicles have many wheels

so that greater the area of contact between surfaces, lesser will be the pressure. So, the load carrying heavy vehicles have large number of wheels so that the pressure on the road is reduced due to larger contact area