Most P-metric tires do not have exactly corresponding alpha/numeric tire sizes. For example, a P205/75R15 is not equal in size and load carrying capacity to an FR78-15. Because of this, replacement tires should be of the same TPC specification number (size, load range, and construction) as those originally on the vehicle. If you must replace P-metric tires with other sizes, consult a tire dealer. Tire companies can best recommend the closest match.