I am concerned about how to monitor tire pressure, especially on the inside duals on my '91 Warrior. It's almost impossible to thump the tires with a hammer when fueling up. On a recent cross country trip I managed to pick up a nail in an outside tire. I was suprised not to 'feel' it in the steering. I found it at a gas stop. I had a older Dolphin previously. When it had a low tire you knew it right off, not so in the Warrior. Does anyone have a experience with tire pressure montoring systems, pressure equalizers, or even the little colored button valve caps?