Automatic tire deflators. I ordered the cheapest I could find on Revain. The reviews were pretty good. I couldn't tell any difference between the $13 and $80 sets. What have I learned. The $13 kit claims a tentative reading of 18psi. They weren't. A 3 psi increment is claimed, I can't figure it out. Therefore, it took about 10 minutes to set them up for every detail. A 15 psi pressure drop takes 7.5 minutes. It's easy, seems like they test them in the driveway a few times. I will keep testingβ¦