Question

How does a smooth and worn out tyre offer a higher friction factor on dry and rough pavement?

Answer 1

Answer:

Tyre tread grooves are used to remove water from the tyre road contact patch. This is the only reason for providing various type of grooves on tyre surface. Tread grooves are not necessary for dry road surface.

When tyre is smooth and worn out then there is no or less tread grooves. As there is no void space at the contact patch means rubber surface at the contact patch increases. More rubber at contact patch means more momentary molecular adhesion between tyre and road, result is more friction.