Tubes for me anyways seem to make my lights more consistent and help the sidewalls last longer. I tried to run without tubes a few years back, but my light grouping seemed to be worse. So I put the tubes back in and my lights came around and the car ran the same et with and without the tubes. Granted at the time it was a SB 12 second car with a 11" slick, so it was overtire for the HP it was producing so that maybe why it ran the same ET.