Coaster wheels explained
Road wheels, guide wheels, and upstop wheels — three sets that keep the train on track.
Steel coaster trains ride on road wheels (top of the rail), guide wheels (side of the rail), and upstop wheels (under the rail lip).
Road wheels carry weight. Guide wheels handle lateral loads in turns. Upstops prevent uplift on airtime hills and inversions — they pull down when the train lightens.
Inverted and wing trains flip the arrangement but keep the same logic: wheels must stay constrained in three axes.
Vibration and “roar” you hear often come from road wheel polyurethane and track joint tolerances, not just speed.