Louis de Carteret

Why not make mixed beef and pork "tyre burgers". Make a doughnut of seasoned ground beef and fill the hole with seasoned ground pork. When cooked you'd still be able to see the difference in colour and get the wheel/hub effect. They should hold together pretty well if handled gently. You could even mix up a few food colours to get a blackish tint to add to the ground beef. Good luck!