ObjectTemplate.SetStrength

MDT description

The Grip property makes the wheel roll as the vehicle moves (provided it's occupied) and the strength and damping (SetDamping) set the characteristics of the spring. A higher strength means increases the reaction of the spring, as it releases after being pushed in and the dampening smooths the motion a little. At high strength the vehicle tends to bounce in a jittery kind of fashion.

Source and more details