Tread wear bars appear when tires are worn down to __ inch of tread a) 1/16 b) 1/4 1/2 d)1

The correct answer is a) $1/16$.<br /><br />Tread wear bars, also known as tread indicators, are raised sections within the tire's tread grooves that indicate the tire is worn down to a depth of $1/16$ of an inch. When the tire reaches this depth, it is considered legally worn out and must be replaced for safety reasons. These bars are designed to provide a visual warning to drivers that the tire is no longer providing adequate traction and should be replaced soon.