if you're on stock tires/wheels, use what is indicated by the manufacturer on the door jam / manual. period.

 

Is this a joke, 45 PSI in your tires? First of all the ride quality must really
suck, not to mention the centers of your tires will go bald long before the
tires are actually worn out....that's just dumb! On your sidewalls it tells you
what the maximum PSI is for each tire, that has nothing to do with what
should be run in the tire....18/19" shouldn't run over 35 to 37 PSI!
Gary

 

also think of the coditions you are measuring your tires at (cold/hot). If you've been riding on your tires all day, it should be higher since pressure increase with heat, vice versa.