Lesson 10 of 12 · Automotive basics

Different speeds. One corner.

3 min20 XP3 questions

Two driven wheels turn through the same corner. Why do they need different rotational speeds?

In a corner, the outside wheel travels a longer path than the inside wheel. A differential lets the driven wheels turn at different speeds while transmitting drive. Its exact layout depends on whether a car uses rear, front or all-wheel drive.

The idea

The outside wheel follows a longer path in the same time. A differential permits different driven-wheel speeds while transmitting drive.

An open differential and a limited-slip differential use different strategies for torque distribution. A generation code alone does not tell you which configuration a vehicle has.

Think it through

Sketch two arcs around the same corner: one for the inside wheel and one for the outside wheel. Which is longer? What must differ if both wheels finish the turn together?

Show the reasoning

The outside arc is longer, so the outside wheel needs to cover more distance in the same time. The differential allows that wheel-speed difference.

Take away
  • Compare the paths before comparing wheel speeds.
  • Check the exact differential type in vehicle documentation.