Based on the latest available science and improvements in tire testing standards developed by NHTSA, Suburban Tire’s new policy regarding tire aging and replacement is as follows:
Suburban tire will “suggest” replacing a tire once the tread depth is 5/32nds of an inch, and will “recommend” replacement at 4/32nds or less, due to significantly increased stopping distances in wet weather conditions as a tire’s tread wears down. For Michelin Premier tires, the “suggested” tread depth is 4/32nds and the “recommended” tread depth is 3/32nds.
Tires over 10 years old should be taken out of service no matter the depth of the tread, as tires over 10 years old are much more likely to catastrophically fail due to tread ply separation. This is based on testing and recommendations of Ford and Michelin, and is consistent with NHTSA data.
Suburban Tire recommends replacement of tires after they have been in service for 6 years, unless they have been inflated with Nitrogen and consistently maintained over their lifetime with monthly air pressure checks. In this case the recommended service life can be expanded to 8 years if the tread rubber is still supple and the tread depth is over 4/32nds.
Suburban Tire will not perform puncture repairs on tires over 6 years old, or on tires with less than 4/32nds of an inch of tread, due to the increasing likelihood of tread ply separation as a tire gets older and wears out.
These same standards apply to spare tires, as they are just as prone to failure as tires placed in service on the road. This is due to the higher heat they are exposed to from the road, the muffler, and the warmth trapped in the trunk. The heat bakes the tire and reduces the bonding action between tire components.
Steven M. Leffler
Owner, Suburban Tire Company
July 25, 2017