In a chain drive, what happens to the sprocket ratio when torque increases?

• A. Increases
• B. Decreases
• C. Stays the same
• D. Becomes negative

Answer: (A)

The main idea is that the sprocket ratio is set by the physical sizes of the sprockets—the number of teeth on the driving and driven sprockets. That geometric relationship determines how fast the driven shaft turns for a given speed of the driving shaft. When torque increases, you’re loading the system more heavily, which raises chain tension and can affect friction, stretch, or the possibility of slip. But these factors do not change the fixed tooth-count relationship; they only influence how effectively that ratio is realized in practice. So, in ideal conditions, the sprocket ratio stays the same regardless of torque. If you ever observe a change in the measured ratio, it usually points to chain slip, wear, or excessive elongation rather than a true change in the gear ratio.