Traction control - it CAN let you down

 
Date: Monday, 27. November 2006

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Maybe, says auto writer Gerry Malloy, we have delusions about how effective technology can be, and our over-confident reliance on it can get us into trouble. " I've been stuck twice this winter, once with a rear-wheel-drive car, once with a front-wheel-drive," writes Malloy in a recent Toronto Star article. "What the two had in common was that both were equipped with traction control." And, adds Malloy, he got stuck because he had traction control, not in spite of it!

Traction control, says Malloy, is like ABS in reverse. By making use of the anti-lock brake system's sensors to determine differences in wheel-speed, it can determine if one wheel is rotating much faster than the others. If the brakes are not applied, it correctly that wheel is spinning and shifts power to the other wheels.

Traction control can manage wheel spin and power transfer in two ways: It can apply the brakes to the spinning wheel(s), thereby shifting power to the other wheel (because that's the way cars are designed); or it can reduce engine power, making it less likely the wheel will overcome available traction

Malloy got stuck on very slippery surfaces – one with fresh snow over ice, the other with deep slush. In each case he was driving slowly and had to stop the car. Then he couldn't get it going again, because the traction control both prevented power getting to the wheels and applied the brakes to prevent wheelspin.

He was only able to bring his old-fashioned "rocking the car" technique into play by switching off the traction control. Rocking the car, for those not familiar with the technique, means using whatever little traction and movement you've got to "rock" the car back and forth. If you're in a snowdrift, this means, almost literally, building a little piece of roadway in the drift that allows you to gain enough speed to escape.

In a situation like this, wheelspin is your mortal enemy (you'll only dig in deeper and melt the snow/ice, making the surface more slippery). It takes a delicate sense of power and control (and sometimes much patience – because you have to build your little road an inch at a time) to pull off the rocking technique. However, as Malloy points out, in some situations, human techniques are superior to the mechanical technology. You just have to stay on top of both.

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