The primary contributor of skin color is the pigment known as melanin. The quantity of melanin in the skin varies based on genetic factors and is also dependent on the degree of sun exposure. Melanin is produced by specialized pigment cells known as melanocytes.
Average new tires used on cars typically start with 10/32 to 11/32 of original tread depth. Tires are considered worn out. In most States when they reach 2/32 of remaining tread depth. Ans 2 - Here in Canada (and I'm sure in many parts of the US ) we get a lot of rain.
Inspection. Tread depth may be measured in sixteenths of an inch, with 5/16 inches being a common depth for a new, all-season tire. Tires are generally unsuitable for snow and rain when their tread depth is less than 3/16 inch, due to the greater traction these conditions require.