Any body got any tricks to inflating the tires on a 3500? I pump mine up when hauling & then back the pressure off when traveling empty. I bought some valve extensions at Campers World that don't work well. I just spent 1/2 hour raising the pressure from 55 to 70 on the rear tires. The valve stems are so stiff it's hard to get the aire chuck (truck type) to seat so the tires will take air & next to impossible to get a reading with the guage I have.