Tyre pressures are only a recommendation/Starting point. As I let my weight get the better of me I added an extra pound to the front and a couple of pounds to the rear from the WSM 33/36 Lbs. As I'm on a weight loss kick I'll be dropping them to suit. If you see near the end of the life of the tyre uneven inner/outer tyre wear you may know if you have been running too low or too high.
As I do my own Tyre changes I also fitted a 90 Deg Valve which makes putting air in a doddle,
HTH
