George, I come from a background of full sized cars, I built cars and crew chiefed a dirt late model for a few years. Do you change tire starting pressures when you run tubes. When we ran them the tires would heat up much faster and more due to the friction even using powder in the tire. We would generally set up a few lbs lower. Just for example, We may start at an air pressure of 10LF, 12-14RF 6-10LR and 14-16RR. If we ran a tube (sometimes to help them get heat in the tires) we would start at 2-3lbs less in any tire that had a tube.