Every other year or so, the same site/email/thread/rumor goes around:
“Did you know that your car’s ABS system actually makes driving in snow WORSE?! And the worser part is, you can’t even turn it off! Automakers and the government are the worstest!”
Except that’s not true.
The origins of the rumor are relatively easy to find:
“And in cases of limited traction such as snow, ice, and mud – ABS is actually detrimental to your safety, as it significantly (and needlessly) increases stopping distance.” (Emphasis theirs.)
“Ive (sic) been driving on ice for over a month and another 2-3 month to go. I just dont (sic) like the jeep deciding how my brake is going to work,” a CarTalk Forum user wrote.
“I have done my homework, and I wish to safely disable ABS on my vehicle. If I could “tune” the ABS to activate farther down the pedal as to only kick in during panic stops, that would probably work as well.”
And so on.
“I would say it’s an extremely bad idea,” said Mike Rizzo, Technical-Fellow for Chassis Controls at General Motors. “If I’m driving and let the front axle lock before the rear axle, I’m going to get into a situation where I have terminal understeer … and the vehicle is not going to want to turn.”
Short answer: Steering > No Steering. Disabling anti-lock brakes also disables traction control, which the National Highway Traffic Safety Administration estimated reduces fatal vehicle crashes by 30 percent in sedans and 63 percent in SUVs.
Rizzo said he frequently hears the questions, and the logic behind disabling ABS isn’t entirely unfounded: Piling snow in front of dead-straight wheels would shorten braking distance. Digging in is better. Threshold braking makes for safer stops.
“In all reality, the computer is better and designed to (pump the brakes) faster than you can,” he said.
Rizzo said he’s often asked why engineers can’t program an ABS controller that could recognize when the wheels are straight and allow drivers to lock up wheels to “wedge” snow in front of the wheels.
“That’s technically correct in a test environment on a highly deformable test surface — meaning you can get a ‘wedge’ in front of a tire — but I would say that’s more applicable to gravel than snow. Snowy surfaces are generally more polished, even with just a little bit of traffic on them,” he said.
Even with studded tires, rotating wheels are directly proportional to steering control. Locking wheels effectively makes the car uncontrollable.
“When you get on very slippery surfaces and lock the wheels, it can take seconds for those wheels to start spinning back up to the velocity of the vehicle. There’s not a lot of road friction to push back on the tire to start spinning them back up,” he added.
Same goes for threshold braking.
“You go back 20 to 30 years and people were taught to ‘pump the brakes’ on snow to lock up and then release the wheel to get it back up to spinning with the rest of the car. That’s what ABS is doing — and it’s much faster,” he said.
For new drivers, or drivers new to snow, Rizzo said it’s best to practice in parking lots to understand how to better control cars in slippery conditions. Slowing down and steering into shoulders is more effective than locking up wheels, he said.
Or, again: Steering > No steering.