The Prius OEM tires are Bridgestone Potenza RE92 (175/65R14) Low-Rolling Resistance (LRR) tires. They have an 84S speed/load rating, 160 treadwear rating, 50 psi max inflation, and an expected life of 30,000 mi.

Toyota recommends only 35 psi, but Prius owners have found this results in uneven tire wear and shorter tire life. I use 42 psi in the front and 40 in the rear. As a result, my tires have lasted longer than expected. I replaced them with new Potenzas in April 2005 (46,000 mi) and March 2008 (90,000 mi or 44,000 mi of tire life).

Some Prius owners have experimented with other tires that have higher treadwear ratings (i.e. longer lifespan). However, none of the comparably-sized alternatives are LRR (except for some Nokians that are marked for summer use only, and I don't have room to store a second set of snow tires in my garage).