The weight of the flywheel is crucial to the performance of an exercise bike. The flywheel is a weighted disk that helps create momentum as you pedal. A heavier flywheel provides a smoother, more consistent ride by eliminating any jerky movements or inconsistencies in pedaling. It also simulates the feel of riding a real bike where you must generate momentum with each pedal stroke. A lighter flywheel may produce a less smooth ride, be less stable at higher speeds, and provide less resistance, making your workout less effective.