Dealer had my tires set to 28 PSI - My 2005

If the tires are overinflated, the sidewalls don't flex like they should, and more of the impact energy gets transferred to the vehicle. This can cause rattles. As for the classic Prius, the tires on it are quite narrow, and despite the higher sidewall rating, they wore extremely fast, with some not even getting 20k out of their tires. When I found John's site, and the results of other classic Prius owners experimentation with higher tire pressures, I followed suit with mine, and have run them from 44/42, nearly from the beginning. At 32k on mine, I have 1/16" tread depth left over the wear bars. Since I have an unevenly worn tire on mine from an encounter with an already dead animal on the road, I will be replacing them in the next week or two, so that I'll have good rubber for my next trip to Colorado, about three weeks from now.