It's not at all that difficult if you do so while the tires are still cold and with a very good quality gauge. I check and adjust mine all the time in the garage (due to outside air temperature changes) getting accurate results with zero difficulty. I also knows that my TPMS system always reads one pound of pressure LESS than my quality gauge and fill accordingly. Been doing it for almost 13 years successfully. And obviously as the tires heat up from either driving or sitting in the sun, the readings will change.