Well if you look at the tire you will see the reconmended tire pressure is on the side wall. Generally it will say inflate from 35 to 65 max psi. I'm 170 lbs., so on my mtb I would inflate the tires to about 55 psi for the road. But if you are on the heavier side I read somewhere that somewhere closer to max would be more beneficial to you. But if the tire is old 55 or less psi is fine. And having a front shock also makes a difference to how much psi is doable. With shocks more psi is doable for the reason of less stress to the tire and ride.