Contributing Writer: Craig Fitzgerald
Ok, here’s the short answer: No, you do not need to pump your brakes.
The reason why requires a lot of background and explanation, but we wanted to get that out of the way for the short-attention-span people in the audience. Understanding why you don’t need to – and why it’s actually detrimental to your braking and steering performance – requires some knowledge of the braking system in your car.
Why Did My Dad Tell Me to Pump My Brakes?
The reason most people still think they need to apply brake pressure, let off, and apply it again is almost 100 percent the fault of the nation’s dads.
We’re not saying dads are always wrong (your author is a dad, for example, and he’s never wrong) but on this fact in particular, what was once good advice is now outdated, and frankly dangerous.
The idea behind pumping your brakes is a good one, even though most of the time it was done incorrectly. The more accurate term for pumping your brake pedal is “threshold braking.” Threshold braking is the practice of applying nearly full brake pressure to the point where the tires are just about to lose contact with the asphalt, then releasing enough to keep the wheels rolling, then applying brake pressure again to just the point where the tires are about to skid.
What threshold braking allows the driver to do – and this is important – is NOT to shorten braking distance. Braking distance may in fact be shorter if you fully locked all four wheels and skidded to a stop. If you watch any of the old road test videos from the television series Car and Track, full four-wheel lockup was how they measured a car’s shortest braking distance:
No, what threshold braking allows the driver to do is slow as quickly as possible WHILE STILL MAINTAINING THE ABILITY TO STEER.
Tires and Your Contact Patch
The contact patch on your tires – the small handprint-sized portion of the tire that is in contact with the road as the wheel turns – can do multiple jobs at once, under certain circumstances. They can steer the car, and they can reduce speed through braking, both at the same time.
But they can only do multiple jobs if they’re not overtaxed taking care of one of those jobs. If your tires are in full lockup, you have completely lost the ability to steer, and that’s bad news when you’re trying to avoid a car that’s come to a complete stop in front of you on the highway. In a situation like that, you want to slow down as quickly as possible, but you also want the ability to swerve left or right to avoid hitting the car in front of you.
That’s where pumping the brakes is effective. If you heard about pumping the brakes from your dad, it was probably in relation to slowing down when driving on snowy or icy surfaces, but the practice used to make sense in all driving conditions. In snowy conditions, it tended to happen at slower speeds, but the practice is exactly the same when you’re trying to execute a controlled swerve around an obstacle at highway speed.
The problem is that while most dads learned to drive in the Mesozoic era, a lot of technology has arrived since then that automatically allows the driver to brake at the threshold, simply by applying full braking force to the pedal and holding it there.
Antilock Brakes and Threshold Braking
Beginning in the late 1980s, antilock brakes (ABS) began arriving as a standard feature and is completely ubiquitous among cars built after about 1996. Unlike most safety equipment that was mandated by the DOT or NHTSA, ABS never was. Components that rely upon its sensors are, though. Since 2012, for example, traction control has been mandatory on all vehicles sold in the United States as standard equipment. Traction control relies upon the wheel speed sensors that ABS uses, so as a result, ABS exists on just about everything as standard equipment.
What ABS does is automatically brake at the threshold at which the tires nearly start to lose traction with the road surface. Then they release quickly, and reapply brakes, again and again, essentially pumping the brakes for you while you simply hold your foot to the floor on the brake pedal.
When ABS was first introduced – and still today – drivers were confused about what it was doing. Early ABS only cycled on and off full brake pressure several times per second, and drivers reported that their brake rotors must be warped because their brake pedal was vibrating when they tried to stop quickly. That was the system doing exactly what it was intended to do. Current anti-lock brake systems cycle at something like 15 times per second, so the vibration is much less severe, but people are still confused about how it works.
New Technology Helps Even More
Soon after ABS arrived, it became evident that drivers had trouble changing their habits. They’d either continue to pump the brakes, even though they didn’t need to, or they’d let off the brakes entirely. The research into this behavior was part of a comprehensive study by NHTSA in 1999.
In order to combat this and provide full braking in emergency situations, manufacturers began to include features like pre-collision braking. Pre-collision braking monitors the closing rate between you and the object you’re about to hit, as well as how quickly your foot leaves the accelerator and hits the brake. If the system senses you need to stop in a huge hurry, it applies 100 percent braking force, whether you stand on the pedal or not.
When In Doubt, Steer Around the Obstacle
It’s spelled out clearly in training documents like the “Driving WIth Four-Wheel ABS Fact Sheet” distributed by the State of Texas. “Don’t forget to steer. If you need to manually steer while the ABS is working to avoid an obstacle in front of you, avoid sudden or drastic steering changes, and carefully guide your vehicle where it needs to go.”
In an emergency stopping situation, apply full brake force and steer around the obstacle with your foot fully engaging the brake pedal. ABS is going to monitor whether or not individual wheels are about to skid, releasing brake pressure on those that are. Your job is to keep your foot down and steer around whatever might be in front of you. Always be looking for a way around, and don’t fixate on the obstacle in front of you.
Why Tires are So Important to Braking
Obviously, your brake pads, rotors, calipers, drums, shoes, and hydraulic system are all important to stopping as quickly as possible. But the single most important thing in your arsenal is the condition of your tires.
Worn tires are not going to allow you anywhere near the braking performance that your car is capable of. Tire Rack tested new tires with a tread depth of around 10/32”, half-worn tires with around 4/32”, and tires that had been worn down to the wear indicators, which tell drivers that it’s time to replace their tires. That depth is about 2/32”.
The tire retailer found that at 70 mph, tires with 4/32” of tread depth came to a stop nearly NINETY FEET shorter than the same car with the same brakes and tire brands, but worn down to 2/32”. To put that into perspective, 90 feet is about six car lengths. That is the difference between making it home safely and getting an expensive ride on a flatbed, at best.
Many people experience their ABS working perfectly well and assume they have a brake problem when in actuality, the wet performance of their tires has seriously diminished.
The bottom line: If you’re driving a car with ABS — and that’s pretty much every vehicle built since about 1995 – DO NOT pump your brakes. Instead, apply full braking pressure, and steer around the obstacle in front of you, whether it’s a car stopped in your lane of traffic, or a deer jumping out of the woods beside the road. Full brake pressure is going to stop you faster, and allow you to safely swerve, rather than plowing directly ahead with the brakes locked.
And finally, replace your tires if they’re questionable.
Craig Fitzgerald began his automotive writing career in 1996, at AutoSite.com, one of the first online resources for car buyers. Over the years, he’s written for the Boston Globe, Forbes, and Hagerty. For seven years, he was the editor at Hemmings Sports & Exotic Car, and today, he’s the automotive editor at Drive magazine. He’s dad to a son and daughter, and plays rude guitar in a garage band in Worcester, Massachusetts.
