You are right , Last sunday , i visited murree, n because of their cold temp ,AIR PRESSURE went very low ,Like 20 psi ,Then on coming back to lahore ,I Again ,filled it up at 32PSI , During driving on motor way , i felt ,car is kind of jumping , then i rechecked ,DUE To hot weather of islamabad ,n so on area , It again went to 40psi Plus , I Again reduced it further to comfortable level , That was 33 psi