Adding pressure will make the car faster if you can keep em glued. From my experience w/ the radials, they will still hook really good down around 17 psi, but the track and your suspension better be good if you're gonna hook them w/ high pressure. That's why I said leave em alone at 18 psi if it hooked b/c you're only gonna get one time shot before eliminations. First round is not the time to try something new.