I have been trying to impress the Bloodhound team with the importance of investigation of the instability of rotating wheels on a surface, otherwise known as shimmy or wheel flutter. As an aerodynamicst you might be able to introduce them to this subject as a wheel flutter situation, due to the supersonic air-speeds and forces around the wheels (as well as the mass and stiffness contributions to the dynamics of this motion). I see this problem as needing a solution before high-speeds are reached, so that the potential risks are minimized and the shimmy boundaries properly defined.