I checked the air pressure in all four tires today and most were between 28 and 30 psi. I aired up the first three to 33 psi and went to the fourth tire and very surprisingly it had only 20 psi in it. I looked it over and at just 1700 miles found a nail right in the tread area. Just had it repaired but this is why I have advocated that the TPMS sensors are very worthwhile. I could not observe by sight or by pressing on the side of the sidewall that it was this low. Since it was on the left side of the vehicle it would have presented a dangerous situation to change the tire on the side of the road. I would suggest everyone consider the advantage of having these. Had I had to drive on the tire and wheel while going flat it could have ruined both not including the danger inherent in this situation. I have driven over a million miles in my lifetime and knock on wood I've never had a flat while on the road. But there is always the first time. Thought this would be of interest here.