1997 Lexus SC 400 Owners Manual - Page 231

CHASSIS CHECKING AND REPLACING TIRES When to replace your tires If a tire often goes flat or cannot be properly repaired due to the size or location of a cut or other damage, it should be replaced. If you are not sure, consult with your Lexus dealer. If an air loss occurs while driving, do not continue driving with a deflated tire. Driving even a short distance can damage a tire beyond repair. Any tires which are over 6 years old must be checked by a qualified technician even if damage is not obvious. Tires deteriorate with age even if they have never or seldom been used. This also applies to the spare tire and tires stored for future use. Replace your tires when the tread wear indicators show. The location of the tread wear indicators is shown by the "TWI" or "∆" marks molded on the sidewall of each tire. The tires on your Lexus have built-in tread wear indicators to help you know when the tires need replacement. When the tread depth wears to 1.6 mm (0.06 in.) or less, the indicators will appear. If you can see the indicators in two or more adjacent grooves, the tire should be replaced. The effectiveness of snow tires is lost if the tread wears down below 4 mm (0.16 in.). If you have tire damage such as cuts, splits, cracks deep enough to expose the fabric, or bulges indicating internal damage, the tire should be replaced. Uniform tire quality grading This information has been prepared in accordance with regulations issued by the National Highway Traffic Safety Administration of the U.S. Department of Transportation. It provides the purchasers and/or prospective purchasers of Lexus vehicles with information on uniform tire quality grading. You Lexus dealer will help answer any questions you may have as you read this information. DOT quality grades - All passenger vehicle tires must conform to Federal Safety Requirements in addition to these grades. These quality grades are molded on the sidewall. 222