Having 3 sets of SMPs, though all 700x 25 or 28mm I run mine consistantly 10-20 psi over recommended specs because of the rolling resistance the tire thickness creates. No probs, so far. If your tires call for 75 psi max, running them at 90 shouldn't present any significant problems. They're very tough tires and the sidewalls are made to standup to alot of abuse. You can always back down the pressure if the ride seems a little too stiff.