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Whoa

From the Driver’s Seat by Chuck Tucker ©2005 – Whoa

Chuck Tucker
Chuck Tucker

I’m just back from instructing at Mid-Ohio, where I was surprised by the results of a braking exercise we did with the first-time students. These students were hard-driving, autocrossing, gas-pedal-loving Car People – and none of them had any idea how hard they could really apply the brakes. Braking is a very useful skill. Being able to slow the car quickly, under control, gives you options that other driver’s don’t have. The goal is to make the wheels rotate about 15% slower than the car is going, but not to lock the wheels and slide. There are three elements: managing weight transfer, knowing when to let up, and braking straight.

If you jump on the brakes suddenly, putting full pressure on the brake pedal immediately, you will lock up the front wheels. Instead, build pedal pressure on the pedal gradually. As you apply the brakes firmly the car will begin to slow, weight will transfer to the front wheels, and the nose of the car will drop. Once this has happened, squeeze the pedal harder. With more weight on the front, you can use more pedal pressure without locking the wheels. This whole process, from first touching the brakes to full pressure, will take at least a second. It often feels like braking twice: press once to put the nose down, then press more to really slow the car.

If you press the brake pedal hard enough to activate the ABS, and you really need to stop the car, don’t let up. The ABS is doing at least as well as the best you can do, and you should let it finish the job. If you’ve never felt your ABS activate before, find a smooth, straight empty road or a big parking lot, get the car up to about 45mph, and stomp the brake pedal as hard as you can. Most ABS systems make a harsh buzzing sound and vibrate the brake pedal. Learn what that feels like, so that you don’t let up on the pedal, thinking something’s wrong, when you should be pressing it to the floor.

If your car doesn’t have ABS you may occasionally lock up a wheel. A locked wheel give a peculiar feel to the car that you’ll learn to recognize, and a characteristic sound. Suppose that 100% represents the perfect braking pressure, but you applied 110% and locked up a wheel. You need to reduce the pressure to about 75 or 80% to get the locked wheel rolling again, then squeeze down closer to 100% to slow the car. If you want to practice this, a wet parking lot is easier on your tires than dry pavement and will let you do the whole thing at lower speeds.

Finally, you can brake hardest when the car is going straight, and you cannot turn the car when braking at maximum pressure. I’ll explain why next month. Until then, keep your eyes up, drive safely, and enjoy.

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