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.
You can make sure that the tread on your existing tires is safe by checking it at least once a month when you check your tires' air pressure. Start by culling out the riskiest rubber. Look for bald tires by checking whether any of the wear bars are flush with the tread's outer surface. Another way to check whether your vehicle's tires have reached their wear limit is to insert a penny into each groove, Lincoln's head down, as shown below. Replace the tire if the top of Abe's head becomes uncovered by any of the grooves.