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is traction control your worst enemy in the snow? Monday, 02/02/2009 by nik
Traction Control is fitted on many modern cars, designed to help prevent and control skids and loss of traction. It may not however be your best friend in the snow.
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The issue that you may face is that when the traction control detects slip at the wheels, it reduces the power to the wheel. (This can be by cutting power at the engine, or on more sophisticated systems by braking the slipping wheel).
On the whole this would seem to be a good thing - when setting off, for example, it reduces slip. If you accelerate it can also control slip. And if the car teeters sideways, then the correction at the wheels is intended to bring it back on track (and generally does. I once tried putting my Saab 93 Aero sideways in the snow using the handbrake - with ESP on I barely got more than 30 degrees out of kilter. With it turned off, I nearly totalled a road sign.)
So why is reduced power to the wheels a bad thing? One word: hills!
Trust me - this is the word of someone who has, in the past, become stranded on hill because he couldn't turn the traction control system off fast enough (a system limitation, I might add). You see, what happens as your car begins to climb a slippery hill is the drive wheels, not surprisingly, begin to slip - especially if the car is front-wheel drive. As they begin to slip the traction control system reduces power. But you're going uphill - so reduced power means you slow down. And if this process continues, before long you can be stationary. Then you might not get going again.
You might argue that the traction control detects loss of grip, and if there is no grip you can't get up the hill anyway. Well, it's not necessarily true. The traction control system is not able to perfectly measure the co-efficient of friction between the wheels and the snow and also has a necessary characteristic called hysteresis. In simple terms, it's only an approximation- it might not know, for example, that spinning the wheels to dig down through the surface snow might find grip underneath; it will never let you do this.
So, be warned. I don't recommend turning your traction control off in slippery conditions, but be ready to turn it off if you are approaching an upward hill. Check, too, that your car allows you to do this - some cars only allow it when they are below a certain speed. As ever, be prepared.
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