Should you pump the brakes in snow, or apply steady pressure?

Dear Car Talk

Dear Car Talk | Feb 01, 2003

Dear Tom and Ray:

Last weekend, my fiancee and I were driving to the school where she teaches, in central Indiana. The back roads were still covered in mostly packed snow, with some ice underneath. As my fiancee approached a stop sign or turn, she would press the clutch in and pump the brakes. I told her that you're never supposed to pump the brakes on a snow-covered road, because it allows the wheels to temporarily lock up and start to skid. I told her to instead apply gentle, constant pressure to the brakes and leave the clutch engaged so the wheels are turning all the time, only disengaging the clutch when the car is almost completely stopped. By the way, her car is a lousy 1997 Saturn SL2 that uses about a quart of oil every week. So, which one of us is right? I think I proved I was right while driving on a road with the same conditions. I applied gentle, constant brake pressure, and the Saturn stopped perfectly, without any skidding or sliding whatsoever. -- Terry

TOM: Well, you are right, Terry. And I hope that knowledge warms you while you're sleeping in the garage for the next few weeks. Actually, Terry, she's right, too, under certain circumstances, so I think you two can still go ahead and send out the invitations.

RAY: In general, in the snow you want to do everything smoothly and gently. Think about walking across an icy pond. What do you do? Do you run and then try to stop short or turn suddenly? No. You'd fall on your butt. You move carefully, doing everything slowly and smoothly. And the same is true for how you drive on ice and snow.

TOM: So, when coming to a stop on snow or ice, you want to anticipate the stop as early as possible, then slow down smoothly and gradually over a nice long stretch of road, leaving the clutch engaged so you get the constant engine braking working for you, too.

RAY: In fact, it's not a bad idea to keep the car in a lower gear than normal in the snow. First, it'll help keep you from accidentally driving too fast. But also, you can slow the car by simply letting up on the accelerator, using the engine braking to reduce your reliance on the brakes. So you're right about all that stuff, Terry.

TOM: However ... if you DO start to skid AND you don't have anti-lock brakes, then you SHOULD pump the brakes to stop the car from skidding. Basically, what you're doing is lifting your foot off the brake pedal when you detect a skid and then immediately reapplying it, trying again to slow the car without skidding.

RAY: ABS does the same thing, but it does it automatically and does it much faster and better than any human ever could. So, in a car with ABS, you never pump the brakes. The brakes will pump themselves if they ever need to.

TOM: So, your fiancee's mistake is that pumping the brakes is not a first line of defense. It's a method of controlling a non-ABS car once a skid has already begun. And your mistake is saying that you should "never pump the brakes on a snow-covered road," which is not true.

RAY: And now that you've both proven to be equally flawed beings, may you live happily ever after in blissful and continual forgiveness of each other.

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