Its obvious you did not like my simple answer. Like the last big post it was taken down within hours of me posting but it got the job done. There is no rule that I can think of about the min. diameter of a foam tire? Why is there one one the rubber tire? Just who do you think got rules to include foams when they were totally left out? but he the President ((Mr. Young) does not always answer emails. You might also ask about the min. weight for bodies? where did that come from?It looks like they had problems with the WGT-R guys and maybe it filtered down to this class( but not here in Florida).If you are going to scrap the bodies that light you really have to be desperate to attempt to win a race. Oh well we will see how long this post stays up. still write to your President and region directors - maybe they can help you like mine did .