I have a drum rig setup (the drum has 1m diameter) with a linear ball bearing to apply the normal force to the wheel through weights, i.e. the weights and the wheel both can move vertically. In addition a damper (a damper usually used in motor cycles to damp handle bar movements) with adjustable damping rate is connected to the linear transducer holding the weights.
Just an observation when an „obstacle“ is mounted on the drum surface or the tire on the wheel is not perfectly round (can happen). At certain combinations of normal force, tire, damping rate … the weights or the wheel respectively may begin to oscillate up and down (obviously a resonance of the oscillating system is attained) at a certain speed. Crr then goes up too, i.e. break point conditions?. Increasing speed further and the oscillation stops. Altering weight or damping rate or tire pressure … and the resonance arrives at a different speed region.
Just an observation when an „obstacle“ is mounted on the drum surface or the tire on the wheel is not perfectly round (can happen). At certain combinations of normal force, tire, damping rate … the weights or the wheel respectively may begin to oscillate up and down (obviously a resonance of the oscillating system is attained) at a certain speed. Crr then goes up too, i.e. break point conditions?. Increasing speed further and the oscillation stops. Altering weight or damping rate or tire pressure … and the resonance arrives at a different speed region.