Measuring the deformation at speed is relatively easy in qualitative terms. Place a fixed reference point close to the wheel, but where it will not touch when the wheel is at speed, an visually observe the deformation. Like truing a bicycle wheel. If the wheel always returns to the same size when stopped, you are in the elastic region of deformation. The pneumatic wheel’s change of shape is not a good indicator of it being safer or less safe than other wheels. It is really just telling you it is not as stiff as other choices.