When buying just two new tires, should they be put on the front or rear?

When radial tires are used with bias or bias belted tires on the same car, the radials must always be placed on the rear axle. Never mix radial and bias-ply tires on the same axle. When you select a pair of replacement tires in the same size and construction as those on the car, we recommend you put them on the rear axle. A single new tire should be paired on the rear axle with the tire having the most tread depth of the other three.