I usually run 35 in both the 69 Firebird and my 2000 Volvo....its a good average number...town is good with 32-33, to get nice soft ride, but highway usually requires a little higher psi, tires tend to flatten out with higher speeds...If I know I will drive ONLY highway for a while, lets say a tripp from Houston to Toronto and back, I`d put 37 in...