I'm not super familiar with the KPM's, but I would say start at the sticker pressure, and work around from there. As long as the sticker pressure isn't higher than what's on the sidewall of the tire. If the sidewall says the tire can take 51psi, you should be just fine to start with 40psi in the tire and go from there. Just remember that when you're doing your test rides, the tire will get hot and the pressure will change (that's why you always check and adjust tire pressures when cold). If it were my bike, I would start at 40 and go for a ride (and make sure I could replicate the ride for the rest of my testing), then move in 3-5psi increments until I found a pressure that gave good feedback and a smooth ride. You'll have to set aside a pretty good chunk of time to ride, but I guess that's just the price you'll have to pay, right?
