I would stick with the 26 PSI, a correctly manufactured tire in good condition is not going to fall apart at high speeds. The following is from the former cheif truck engineer at Ford:
"We ran the tests, and in really severe maneuvers, emergency lane-change maneuvers, 35 is not where you want to go," says Ford's chief truck engineer, Tom Baughman.
Generally, lower air pressure makes a tire ride softer and steer sloppier. Higher pressure makes the ride firmer and the steering more responsive. Baughman notes: "You may not want crisp steering in a vehicle with a relatively high center of gravity and relatively short wheelbase. Putting more air pressure in your vehicle is not in the direction of goodness in a vehicle with a relatively high center of gravity."
Ford's lower pressure recommendation makes the truck more stable and "absolutely is not the problem," says Baughman.
That's because the more-responsive steering that generally comes with higher pressures can cause the vehicle to swerve wildly when a panicked driver yanks on the steering wheel during an emergency. He says Ford's policy, therefore, is to specify tire pressures as low as possible that don't compromise hauling ability. "Sometimes you want the steering to be a little bit on the lazy side, for safety," Baughman says.
