Sunday, September 19, 2010

Traction Control

In my earlier posting, I talked about Electronic Stability Control which gets assistance from the Traction Control System with which it is partnered.   I probably should have explained TC first and then gone on to ESP, so consider this a post to fill in the blanks.

If  you go back as far as I do, you may recall rear wheel drive cars (and certainly most trucks) have long employed a limited-slip rear axle which mechanically transfers power to the rear wheel with the most traction, helping to reduce, but not eliminate wheel spin when operating on slippery surfaces. While limited-slip rear axles are still in use in many front- and rear-drive vehicles today, the device can't completely eliminate wheel slip. Hence, a more sophisticated system was needed. 

Enter electronic traction control.  In modern vehicles, traction-control systems utilize the same wheel-speed sensors employed by the antilock braking system. These sensors measure differences in rotational speed to determine if the wheels that are receiving power have lost traction. When the traction-control system determines that one wheel is spinning more quickly than the others, it automatically "pumps" the brake to that wheel to reduce its speed and lessen wheel slip.  In most cases, individual wheel braking is enough to control wheel slip. However, some traction-control systems also reduce engine power to the slipping wheels. On a few of these vehicles, drivers may sense pulsations of the gas pedal when the system is reducing engine power much like a brake pedal pulsates when the antilock braking system is working.

Many people mistakenly believe that traction control will prevent their vehicle from getting stuck in the snow. This couldn't be further from the truth. Traction control does not have the ability to increase traction; it just attempts to prevent a vehicle's wheels from spinning.   For drivers who routinely drive in snowy and icy conditions, traction control, antilock brakes, and snow tires are must-have safety features.

On most cars with TC, you will notice an indicator that flashes when a traction control system activates. This indicator serves to alert the driver to the fact that the car's responsiveness may be impaired due to the loss of traction, and as a warning that the driver may be going too fast. When the system disengages, the indicator will turn off.  If it remains on, there may be an error in the system, and the car should be taken to the dealer for inspection to determine what is causing the light to stay on or to flash.