No rubber for me. At MHIC i ran 2 sets of spec foams in 17.5 the whole time including some practice so 4 quals and a main with some practice. Started at 39.8 front and 40mm rear. I still could do a few more practice runs on them too. Imo wgt-r ruined the class, MHIC had i think 4 or 5 of them. Id still run wgt if crc wouldnt have pushed to make it rubber tire.