Can you tell the difference between 15psi and 17psi? No you can't. We can't either, but our digital gauge can. Today's wider, lower pressure tires are more pressure-critical than back when we just used to put as much pressure in as the pump could stand. It's not about fending off flats these days, it's about grip. And the difference between too much and not enough can be as little as a couple of pounds of pressure. The days of 'giving it a squeeze' are over. You need our help.