When delving into the world of tread designs, one thing that is always fascinating is the size of the contact patch through which the tread design must roll.

On an average-size passenger car tire, the contact patch is about the size of a 4x6-inch postcard. In total, all four contact patches reach about the size of an 8x11-inch piece of paper.

That's precious little rubber-to-road contact, given that the primary purpose of the tread design is to transmit tractive forces, such as braking and cornering.

The second major purpose of the tread design is to provide grip. To pull this together a bit, think of traction as being the hypotenuse of a right triangle. Think of the legs of the triangle going through a corner. The bottom of the triangle (east-west) represents lateral force (encountered in a turn) and the north-south leg (vertical force) would be braking. If you're braking and turning, you are dealing with a tractive force or "tractive vector" in engineering terms. This is nothing more than the hypotenuse of the triangle rolling through the center of the contact patch.

Wear Patterns
Let's look at this yet another way. Good tire techs can visually tell if the tread ribs and blocks are being unevenly worn in an east-west or side-to-side manner. They can also see a heel-and-toe wear pattern, which is more of a north-south phenomenon. All they have to do is rub their hand, gloved or not, across the tread surfa...