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.
Remember, with winter tires only the first 50% of tread is really for use. After that, you have the equivalent of half-worn all-season tires. Blizzak special outer rubber differs from lower layer, too, as the maker informs. Winter tires with 11/32 new tread depth are effectively kaput at 6 or 5 / 32. You should not push regular tires below 4/32 in any case, see wet stopping distances at full, at 4 and at 2 /32 video comparisons on Tirerack.com.