Tires: Wide tires vs. thinner tires, principle of physics, tire traction

Question
Well, I am taking physics right now and my teacher wants us to explain the physics behind why dragsters have increased tire width from the past to present. Is it because wider tires increase grip or friction, and reducing slip which ultimately increases speed?

Answer
Allen,

I think the point that your teacher is trying to make is that it is a principle of physics that friction is not increased by increasing the area of contact.

However, tire traction doesn't relate to friction.

The tread rubber in the tire penetrates the macrotexture of the pavement, and traction is generated by the material strength.  In other words, by penetrating the pores of the road surface, losing traction would result in the tearing of the tread rubber.

So area very much has an effect on tire traction.

HOWEVER, wide tires are also more prone to hydroplaning.  So designing the width of the tread of a tire becomes a problem of balancing conflicting goals.

BTW, the highest tire traction occurs at about 10% slip - regardless of how wide the tire is.  If you watch the tire when a dragster first takes off, you will see the tire slip and this is exactly what they want - just not too much.