The coefficient of traction is defined as the ratio between maximum pull before slippage and what?

• A. The total weight on the machine's drive wheels or tracks
• B. The engine horsepower
• C. The tire pressure
• D. The air temperature in the axle housing

Answer: (A)

The key idea is that traction is about how much pulling force can be achieved before the wheels slip, relative to the downward force pressing those wheels against the ground. The coefficient of traction is defined as the maximum pull before slippage divided by the weight (normal force) on the drive wheels or tracks. So the denominator is the weight on the drive wheels, which determines how much friction is available to resist slip. Engine horsepower measures power, not the grip limit; tire pressure can affect grip but is not the defining ratio; and air temperature in the axle housing doesn’t set this traction ratio. Hence, the weight on the drive wheels or tracks is the correct denominator.