35 PSI max front and rear on my 2.25 Cinders. 40psi max on my 2.3 Weiwolfs. 45 min. on my Trailblasters. I weigh 200 pounds, have Mavic321 rims, and ride aggressive XC. the side walls can make a difference in pinchflats also. my racing weight tires need higher psi to be stable