drivqo.
Drivqo Labs / Experiment 03

One turn. Two speeds.

The outside wheel travels farther in a corner. Explore how a differential allows different wheel speeds while carrying torque to both wheels.

Open differentialTop view of a driven axle with left and right wheels connected to a central differential and driveshaft. Moving tread marks show relative wheel speeds.LEFT WHEELRIGHT WHEELDRIVESHAFT → DIFFERENTIAL → AXLE SHAFTSTOP VIEW · FORWARD ↑OPEN DIFFERENTIAL / SCHEMATIC · NOT TO SCALE
Change one thing. See what happens.

Straight ahead

Both wheels travel the same distance and rotate at the carrier speed.

Try thisChoose a left turn and reduce the radius. Watch the right wheel get faster while the average stays unchanged.

30 rpmLeft wheel
30 rpmRight wheel
The short answer

Why do wheels need a differential?

A differential lets driven wheels rotate at different speeds in a turn. The outside wheel travels farther. In a symmetric open differential, the carrier speed equals the average of the two axle speeds.

Understand the idea

The mechanism,
in plain words.

Different paths

In a left turn, the right wheel is outside the corner and travels farther. In a right turn, the left wheel travels farther. Equal tire sizes need different rotational speeds.

The average stays fixed

In an ideal symmetric open differential, carrier speed is the average of the two axle-shaft speeds. One wheel can speed up while the other slows by the same amount.

Speed is not torque

Different wheel speeds do not mean the outer wheel gets more torque. An ideal open differential applies equal torque to both outputs, subject to available traction.

The traction limitation

If one driven wheel has very little grip, it limits usable torque at both outputs in a basic open differential. Limited-slip devices and brake-based traction control behave differently.

A real cornering relationship Model & sources

Track width is 1.6 m. Inner speed = carrier speed × (1 − 0.8 / radius); outer speed uses +. Equal tire rolling radii and no slip are assumed.

For a turn with axle-center radius R and track width t, the inner wheel follows radius R − t/2 and the outer follows R + t/2. With equal rolling radii and no slip, wheel speeds are proportional to those paths. Dividing by R gives the speed factors 1 − t/(2R) and 1 + t/(2R). Their mean is 1, preserving carrier speed. This derivation assumes a symmetric open differential; it does not model torque losses or tire forces.

What this model simplifies. Kinematic model with equal rolling radii and no tire slip. The turn radius is measured to the axle center, not the steering-wheel angle. Carrier speed is after final-drive reduction. Tread motion is a visual cue; internal differential gears and vehicle trajectories are not simulated.