THe vibration problems that most people experience with the stock tires is due to flat spotting that occurs after the vehicle has been parked for a while. Hot temps. make it more pronounced. To get the speed rating on these tires an overlay belt is built into the tire to keep the tire from growing under high speeds. THese belts are on top of the radial cables and steel belts in the tire casing. THe overlay belts may be made of nylon, rayon, kevlar or other types of material. WHen the truck is parked a flat spot develops and causes the vibration. As the tire warms up the flat spot will go away. Before radial tires were used all tires were bias ply and mostly made out of nylon. THese tires all flat spotted when parked. People back then knew this and just drove the car for a while before they expected a good ride.