About 70psi should be a good starting point. BUT- that's with no load on the machine and the shocks fully extended. Here's what I mean- I have four fill valves- one for each corner- so I can't be sitting in the machine when I adjust pressure. So I put 70psi in the fronts, and then lift it by the front bumper a little by hand, and tweak it back to 70psi. I did the same on the rears but I put them up to 90psi. This past week, I did a couple of hard stops from about 35 mph, and noticed that the front end was 'dipping' to the drivers side, and causing the rear to slide out a bit- this was on a sandy road. so I bumped up the pressure to 75psi in the front drivers side shocks and repeated the test- it absolutely eliminated any 'squirelyness' in near lock-up braking, and the machine stayed absolutely straight. Something else I should mention- I had my Dad sit in the machine- he's about 230lbs- and I re-checked the pressure- 118psi. So my point is this, the pressure rises rapidly as the shock compresses, and, conversely, drops rapidly as the shock extends, so if you were to load the machine (shocks partially compressed), and put 70psi in the system, it would read way below 70psi when the load was removed, and would probably ride like a spongy mess. So, every time I've made a pressure adjustment, I always try to get the shocks fully extended. Once I get the compressor and the rest of the system installed, I'll simply adjust the system for good ride and control, not by reading a pressure gauge, because the pressure fluctuates too much with even small movements of the suspension or a change in load. I really like Chooglin's valve set-up for the non-compressor set-ups. With that style of valve, you could even use a bicycle pump to pressurize the system, close the valve, and not loose any air when removing the fill chuck.