Air pressure for M/T drag radials

Well I'm back. I started this thread and ran at the track then had to leave for 2 weeks. I started at 18psi and spun for 30 ft but only did short burnout. Lowered thru day to 16 as ambient heated up. I did longer burnouts and that seemed to help. It still spun for about 30 ft but at least the 60 ft times were consistent. ET's were fairly consistent about 8.5 for 1/8th. Will continue to adjust when I go back to track. Thanks again for advice.