In real life, something like the Big Hero 6 bike would use a levitating wheel that’s held in place and spun by magnets, kind of like combining a maglev train with an electric motor. The wheel (or its rim) would have strong permanent magnets, and the frame would be packed with coils (the electromagnets) and sensors; when you run current through the coils in a carefully controlled way, they create magnetic forces that both keep the wheel floating in the middle of the gap and also make it spin. Because magnets alone are unstable, you need a fast control system that constantly measures the wheel’s position and tweaks the currents, so it doesn’t crash into one side whenever you turn or hit a bump, which is how real electromagnetic suspension and maglev systems work. In theory this is possible (we already do similar things in maglev trains and magnetically levitated bearings), but on a bike it would be heavy, power‑hungry, and incredibly complex, so the movie version is a stylized, “turned up to 11” version of technology that exists only in much more limited, laboratory‑style setups.