What is the impact of the number of teeth on the front sprocket of a motorcycle on speed?
2 Answers
Motorcycle front sprocket with more teeth will reduce the speed, because the motorcycle has a fixed output power. With a fixed number of teeth on the front sprocket, the more teeth on the rear sprocket, the more powerful the start-up, but the lower the top speed; the fewer teeth on the rear sprocket, the weaker the start-up, but the higher the top speed. The number of teeth on the motorcycle's front and rear sprockets usually differs significantly. The front sprocket (drive sprocket) typically has 13-15 teeth, while the rear sprocket (driven sprocket) usually has 30-50 teeth. Off-road motorcycles often have even more teeth on the rear sprocket to increase output torque for better off-road capability. When modifying sprockets, increasing the number of teeth on the front sprocket or reducing the number of teeth on the rear sprocket can increase the speed at the same engine RPM, but the corresponding output torque will decrease, resulting in slower acceleration. Generally, with the front sprocket size unchanged, a larger rear sprocket will enhance the vehicle's power performance but reduce speed, while a smaller rear sprocket will increase speed but decrease climbing ability.
A motorcycle modification enthusiast with ten years of riding experience tells you: Increasing the front sprocket by two or three teeth can save some RPM when the bike is running at high speed. For example, if the stock front sprocket has 15 teeth, switching to a 17-tooth sprocket can reduce the engine speed by about 500 RPM when the speedometer shows 100 km/h. However, it needs to be adjusted in conjunction with the rear sprocket, otherwise the bike will feel sluggish when climbing hills. I modified the front sprocket of my CB400, and the top speed increased by 7 km/h, but I had to give it more throttle at startup. Note that the chain angle should not be too large; the modification shop said that exceeding 28 degrees will accelerate chain wear.
