| Trans Gear | Wheel Torque |
|---|
From Engine Torque to the Pavement
The torque your engine makes is only the starting point. By the time it reaches the wheels it has been multiplied by the transmission gear and the axle ratio, then trimmed by friction in the driveline. The result, wheel torque, is far larger than the engine figure and is what actually accelerates the car.
Tractive Force and Traction
Divide wheel torque by the tire radius and you get tractive force, the pounds of push at the contact patch. This is the number that competes with weight and grip. A low gear can produce enormous force, but if it exceeds what the tires can hold, the result is wheelspin rather than acceleration, which is why launches are usually traction-limited.
Why Low Gears Feel Violent
First gear multiplies torque the most, so it delivers the biggest shove and the highest tractive force. As you climb through the gears the multiplication falls and the push softens, even though road speed rises. Tire size matters too: a taller tire reduces force for the same torque, trading thrust for top speed.
Frequently Asked Questions
What driveline efficiency should I use?
Roughly 85 percent for a manual or a modern automatic, a little lower for older or all-wheel-drive systems with more components turning.
Is wheel torque the same as axle torque?
Effectively yes at the same point, though wheel torque is usually expressed with the resulting tractive force at the tire, while axle torque focuses on the value delivered through the differential.
Why does more force not always mean faster?
Because tires can only transmit so much before they spin. Past the grip limit, extra torque is wasted, so traction, not torque, sets the launch.