Is it possible the side with the pressure increase was the side that was in the Sun? I don't think anyone else with Nitrogen in their tires has had the same experience with their truck or trailer...DonI thought the Nitrogen was a gimmick also until two years ago. My dodge ram has electronic pressure monitoring. Here in Georgia the road get very hot, so I I inflated my truck tires with regular air on one side and nitrogen on the other. Drove around all weekend and notice the air inflated tires increased in pressure almost 8 to 10 lbs over the nitrogen tires on each trip. Have any of you tried the Carlisle 12 ply for RVs yet????