How traction makes your car slip?

Have you ever experienced to drive your car on wet roads (due to snow or rain) or on roads with low friction coefficient, you may have had a feel of wheel slip. This is where traction comes in play. Traction is actually the force imparted by the wheels on the road or vice versa. Traction is indeed very important in auto designing.

What happens is when you drive the car on a wet surface, traction reduces (the force applied by the wheels on road). In an engine design, traction is always kept higher than the engine torque at all speeds but when traction due to the poor surface contact lowers, torque may exceed and makes the car slip. In short, you may say that when the force provided by the engine to the wheels (longitudinal force) exceeds the force imparted by the wheels on the road, slip occurs. So the term “traction” has the real importance in automobile engineering.

Traction at cornering

You might have seen the racing cars slip at cornering even if the road is not wet. During cornering, lateral force comes in play. This is the force provided by the surface and the wheels to make the car turn. So if you speed up the car at cornering, you are increasing the longitudinal force and if these two forces (longitudinal and lateral) exceed the traction level, car slips.

Watch the video.



The car on the left is equipped with traction sway control system, the one in the middle is to see how the driver responds to slip without the sway system and the one on the right is the vehicle without the system and the result is the car slip.