Traction control, how the system works on cars

Traction control, how the system works on cars

What is the fundamental need of any car on the road? Ensure an adequate level of grip. Whether on a dry, wet, bumpy road. This need is essential to understand why traction control on a car – a discourse that also applies to motorcycle traction control – has over time taken on a relevance that goes far beyond sports cars.


The grip of the car on the asphalt is directly linked to the condition of the surface and the tires, which are the only contact element between the car and the asphalt. Well, in this light, how does the traction control work?

In very, very simple terms, it intervenes to limit an excess of rotation of the wheels with respect to the speed of the vehicle. It can operate on both wheels that transmit traction, or it can only operate on a single wheel. The essential information, in both cases, is the presence of a rotation of the wheel greater than the value corresponding to a given speed.

Read also Driver assistance, the 5 useful ideas in the city

The essential elements of traction control on a car are the sensors that detect the speed of rotation of the wheels and a control unit for processing this data. On how the traction control intervenes on the slippage of the individual wheels, there are various solutions.


How does the traction control work? Once the loss of grip has been detected, therefore on the basis of a single wheel rotation speed higher than the vehicle speed, the control electronics can operate in two ways. The first intervention, classic and largely the most widespread on large series road cars, involves the adoption of selective braking on the wheel in the skidding phase, so as to reduce the relative speed of rotation as long as it does not fall within the limits of the speed of the vehicle. . Traction is controlled by reducing the rotation speed.


Clearly, the possibilities opened up by the combined electronic management of several factors (data, therefore) allow to refine increasingly advanced controls, up to predictive schemes that consider not only the speed of rotation of the wheels but also the speed of the vehicle, the amount of accelerator used. , the flying angle. A complexity that increases with the technical quality and performance level of the cars.


Other intervention systems provide for a control linked to other vehicle components, from the reduction of the torque delivered by the engine to the control of the differential, in more advanced systems. Traction and differential control should be discussed in an in-depth analysis that looks at mostly high-performance models, where the operation of the differential – which is the mechanical organ of torque distribution between two wheels of the same axle, where not between the front axle and rear in 4 × 4 systems allows to transfer the engine torque from a wheel that is slipping to a wheel with greater grip on the asphalt. This control takes place by means of mechanical or electronically controlled differential systems.

vehicle on off road track


If in the past traction control could be spoken of as a system relative to itself, the integration of the management electronics with stability and dynamics control systems involves several systems in a single mission to ensure the car dynamics. always optimal and safe driving.

What is traction control? We have said how it intervenes to prevent the loss of traction grip of one or more wheels, but why is there the need for this intervention? In vehicle dynamics, a loss of traction grip, especially if it occurs in non-straight driving conditions, generates consequences of vehicle instability that can lead to loss of control of the car if not properly controlled. The traction control – and more generally the stability control – ensuring the correct rotation speed of the wheels ensures a stable and safe attitude of the car. The electronics intervene just before the physical limits are exceeded, bringing the car back within safe driving parameters.


The disengaged traction control system allows the driver, usually by means of a button, to override this electronic control on traction, and therefore on the amount of torque transmitted from the engine to the wheels.

Why would you want to exclude such an important support in road driving? While ensuring high driving safety, the traction control of large series cars is still a performance limitation. In conditions such as track use and with adequate driving skills, excluding traction control leaves the driver with direct management of the full potential of the vehicle, without any restrictions whatsoever.


There are also specific driving conditions, in which the support of the electronics, together with precise mechanical schemes, is essential for performance. This is the case with off-road traction control. We are not talking about crossovers and SUVs with dubious off-road qualities, but real 4 × 4 systems, permanent or disengageable, where traction control works in the last resort, to support a transmission of torque to the wheels that it has in the differentials a limited slippage a fundamental aid to maximum traction on the four-wheel drive and very low-grip surfaces.

To say of a single off-road traction control strategy is wrong. In fact, on muddy surfaces or on sand, the specific driving modes deactivate the traction control to allow the wheels to slip and, from this dynamic, allow a part of the accumulated mud to be expelled from the tread.

Low-grip surfaces that can also be driving conditions on snow. The work of the electronics, of the traction control, is not enough to obtain adequate traction. In these extreme scenarios, the importance of the interface between tires and the surface is best explained. With winter tires, traction control can be a little extra help to avoid slippage of one or both wheels, but it does not necessarily solve the car’s difficulties in moving on a very low-grip surface.