Question

why do the tyres of trucks and cars are treaded?

Answer 1

this is done to increase the frictional force between the tyres an road, so that when the vehicle comes down from a steep slope then it gets a better grip with the ground.

Answer 2

This is done to increase the frictional force between the tyres and Road, show that when the vehicle come down from a steep slope then it gets better grip with the ground