What would cause a chain to ride on top of a sprocket?

When a chain is said to ride on top of a sprocket, it typically indicates that there may be a misalignment or incompatibility which can be attributed to the condition of the chain itself. A chain that has stretched over time can lose its intended pitch and fit with the sprocket teeth, causing it to sit improperly. This improper fit prevents the chain from engaging correctly with the sprocket, leading to the phenomenon where the chain appears to ride on top of the sprocket instead of meshing smoothly between the teeth.

As the chain stretches, the distances between the links increase, impacting how well the chain can seat onto the sprocket. If mesh alignment is disrupted, this can result in excessive wear, noise, and even potential failure of the drive system. Maintaining proper tension and condition of the chain is crucial for ensuring it functions as designed and properly engages with the sprocket, which emphasizes the importance of regular maintenance and inspection in any power transmission system.

Other choices may involve components of the system, but they do not directly address the issue of improper fit caused by chain elongation.