Welcome to the wonderful world of Interco Thornbirds.
Thornbirds are an off-road tire with terrible on road handling characteristics, they're trickey to balance, they wear twice as fast as other tires, they chunk when used on road a lot, and they ride rough.
On the plus side if your gonna off road a lot then the Thornbirds are one of the best tires you can get for different situations, they self clean in mud, you can lower the pressure to 10psi in sand and rocks and get terrific traction and not roll a bead, at 20psi they blow through snow real good and dont chunk up when they get to cold, and they have double sidewalls for protection.
But unfortunately most of us spend most of our driving time on road.
Check your tire pressure, the shop may have aired the tires a little high.
The best way to get the correct pressure for your tires is to load the truck like you normally drive it, draw a heavy chalk line about 6" in front of each tire across the tires path, then roll the truck across the chalk line. The tires should have a chalk mark across the tread, if they have to much air you'll only have chalk on the center of the tire tread, to little air chalk on the outsides of the tread, just the right amount of air a chalk line will be all the way across the tire.