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.
Tread is also part of what prevents a vehicle from hydroplaning (aquaplaning), or losing traction when gravel is present on the road surface. Ensure the safety of your vehicle and the safety of your passengers with regular tire rotation, tire tread depth checks and complimentary tire inspections.