There's been all this hype about anti-lock brakes I understand...

Dear Car Talk

Dear Car Talk | Nov 01, 1994

Dear Tom and Ray:

There's been all this hype about anti-lock brakes. I understand that they "pump" themselves automatically to prevent the tires from locking up. When I'm driving on slippery roads, with anti-lock brakes, do I still need to pump the pedal myself?

RAY: Absolutely not, Michelle. If you have an anti lock brake system (ABS), you have to forget everything you learned about pumping brakes. If you pump your ABS, you'll defeat their purpose.

TOM: Their purpose is this: In an emergency--or on a slippery road--when you have to stop suddenly, the wheels can lock up and throw you into a skid. And when you're skidding, you don't have control of the car.

RAY: Without ABS, you're supposed to "pump" the brake pedal. That is, step on it, let up, step on it, let up. If you're very skilled at this, you can maintain some control of the car by letting the wheels unlock long enough to regain some steering control, and then locking them up again to slow down some more. But not everybody can do this.

TOM: ABS not only does this automatically, but does it much better and faster than you or I ever could. It senses when a wheel is just about to lock up, and it releases that brake momentarily and then reapplies it. And instead of pumping the brakes once a second or so, like you or I might be able to do, ABS pumps the brakes many times per second, and works independently on each wheel. And because ABS prevents the wheels from locking up, it allows you to maintain steering control of the car during panic stops.

RAY: So here's the rule. When driving a car with ABS, in a panic stop, just step on the brake pedal and hold it all the way down. You'll feel a strong pulsing in the pedal. Don't be alarmed; that's normal. It's the pumping action of the ABS.

TOM: Geez, you know, they ought to use that as more of a selling point. I mean, people are reluctant to spend $800 on optional ABS. But they might pay $800 for a combination ABS/foot massager! 1997

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