Lionhart follows the recommendations of the industry associations regarding tire life and inspection guidelines. We recommend that, in addition to regular tire inspections, customers have their tires inspected by a qualified tire service person after five (5) years of use to determine if the tires can continue in service. It is recommended that spare tires be inspected at the same time. Further, even when tires appear to be usable from their external appearance or the tread depth may have not reached the minimum wear out depth, it is recommended that all tires (including spare tires) that were manufactured more than ten (10) years previous be replaced with new tires.