This sounds pretty obvious, but lower the pressure until the front feels squirmy when you weight it, then add a couple of psi. The rear should have a few more on top of that. It'll give you a better ride and lower the rolling resistance. Depending on how stiff the casing is, I'd bet you'd be mid 20's or lower with a 2.6. Pump gauges are often inaccurate, so your 30 could be my 25 as well. I have a digital gauge, and my pump runs 4psi low at all pressures.