public float getRollInfluence() {
        return rollInfluence;
    }
the coefficient of friction between the tyre and the ground.
Should be about 0.8 for realistic cars, but can be increased for better handling.
Set large (10000.0) for kart racers

@param frictionSlip the desired coefficient of friction between tyre and
ground (0.8&rarr;realistic car, 10000&rarr;kart racer, default=10.5)
jme3-jbullet/src/main/java/com/jme3/bullet/objects/VehicleWheel.java