Rimpull is defined as the usable force at the point of contact between the tire and the ground.

• A. Usable force at the point of contact between the tire and the ground
• B. The maximum pulling capacity of the engine
• C. The vertical load on the axle
• D. The friction coefficient between tire and road

Answer: (A)

Rimpull is the usable traction force that can be transmitted through the tire-ground contact patch. It represents the actual force that can be applied at the ground to pull or drive the vehicle, taking into account how much grip the tire can develop with the surface and how much load the wheel has to push against. In other words, it’s the real pulling power you get from the wheel-ground interface, not just what the engine could theoretically deliver.

Think of it as the bridge between the engine and the road: the engine may produce a lot of torque, but if the tires can’t grip the road, that force can’t be transmitted to pull. The vertical load on the axle affects how much friction can be generated (more load generally allows more grip up to a limit), and the friction coefficient between tire and road sets the upper bound on that grip. But the usable pull you actually get is the force at the contact patch, not the engine’s maximum rating, not the axle weight alone, and not the coefficient by itself.