I have the "40" lbs set.... and run my tires 44 in rear and 42 in front. I see the green on the stem.... I am good to go. So far, manually checking my tires, I have not seen these miss the mark. Once my front tire was at 36 and it was showing red. I checked my tire and sure enough it was under inflated.
In order for them to work, they have to depress the valve stem. I hope the Chinese made things stand up...or they could in fact cause what we are trying not to cause.... a seriously under inflated tire.
I am going to purchase the Tire Pressure Monitoring System very soon.