A few words about tire grip.
Yes, in a Newtonian sense, the coefficient of friction is unitless and determined by the constant properties of the 2 materials in contact and the force applied to them. In this perfect case, the grip is constant regardless of area in contact as long as the force remains constant. In this mental exercise the blocks are flat and do not change shape or properties.
However, tires aren't blocks in a lab. It's obvious and intuitive if you watch any kind of motorsports that wider tires do indeed give you more grip. They also last longer. I won't fully explain why but consider this first, rubber (especially race rubber) heats, deforms and flows. Now visualize the pavement, it's not smooth. It has nooks and crannies that the gooey mess of rubber can flow into and press against like a foothold or ledge. A rock climber doesn't stick to El Capitan without tiny ledges. The more rubber can get into these crannies, the more it can grip outside of it's straight coefficient of friction. The wider the better.
The harder and colder the tire compound is, the more Newtonian the behavior will be. The hotter and softer the compound, the more other factors come into play.
Quick addition:
Even in the simplified Newtonian definition, you can increase coefficient of friction by making the compound softer and compensate for wear by making it wider.... see how that works too.