Metzler rates the Marathon max at 50 PSI if memory serves...so just adjust to the max that your SEVICE or USER manual references for Solo or 2-Up respectively. Since Metzler rates the max so high, I suppose you have more margin in the upper pressure area, but remember overinflation changes the sidewall profile and will actually LOWER the size of contact patch pattern when at high lean angles NOT for the better! Part of the deal is to have sideways skid recovery...with small tire patch and roll pattern once the skid starts you may not have time to recover.