So having some baseline would still be helpful just to get some sort of reference. For science, you'd put the dampened wheels on a car and get readings from inside the car as that's the only thing relevant. You'd then replace the wheels with non-dampened versions on the exact same car, and then take your measurements from inside the car again.

This isn't rocket science. It doesn't need to be any more complicated than taking readings where your target audience will be sitting. The fact that this even needs to be stated explicitly just makes me sad for common sense