See also:

Tread wear
The tread wear grade is a comparative rating based on the wear rate of the tire when tested under controlled conditions on a specified U.S. government course. For example, a tire graded 150 would ...

Tire tread
WARNING Although the applicable federal motor vehicle safety laws consider a tire to be worn when the tread wear indicators (TWI) become visible at approximately 1/16 in (1.6 mm), we recomme ...

Important safety notes
WARNING Inhalation of exhaust gas is hazardous to your health. All exhaust gas contains carbon monoxide (CO), and inhaling it can cause unconsciousness and possible death. Do not run the engi ...