Brake Assist
by Jim Kerr

Big disc brakes and antilock systems are great for stopping quickly while still keeping the car under control. They have only one downfall: the driver! When a sudden or panic stop situation occurs, most drivers hesitate slightly before applying the brakes firmly. It is only a fraction of a second, but that short time can mean the difference between a safe, controlled stop and bent or broken parts scattered all over the road. One manufacturer is using technology to help.

Mercedes-Benz, among others, now has "Brake Assist" on every model they sell in Canada. Brake Assist applies the brakes with full brake force when it is needed. Electronics are used to control the system and it can react within a split-second. Much faster than the average driver!

So why is Brake Assist such a benefit? Research done by Mercedes-Benz shows that even experienced drivers may not apply full brake force in emergency situations. In fact, 99 percent of drivers were slow to apply the brakes or only applied full brake pressure when it was too late. Brake Assist applies the brake fully and quickly to stop the car in as short as distance as possible.

For many drivers, this means the Brake Assist will provide 45% shorter stopping distances. Even the most skilled drivers find about a 15 % improvement. I know we are all "skilled" drivers, but even the best driver has a bad day, and that is when Brake Assist can be very useful!

So how does it work? The system uses adaptive learning to respond to individual driver's braking habits. Every time you step on the brake, a travel sensor that rests on the internal vacuum diaphragm of the brake booster sends information to the Brake Assist System computer. The computer learns how fast and how hard you normally step on the brakes. It even processes information regarding brake wear and vehicle speed.

When an emergency braking situation occurs, a driver usually reacts by stepping on the brake pedal quickly, but not hard enough. The computer monitors pedal speed through the travel sensor and if the speed indicates an emergency situation is present, the computer will open an electric solenoid on the brake booster. The solenoid lets atmospheric pressure into the rear of the brake booster, causing the booster diaphragm to move forward and fully applying the brakes. Release the brake pedal, and the computer instantly releases the brakes.

The computer that controls the Brake Assist is integral with the Electronic Stability Program computer. Brake Assist takes full benefit of ABS and the vehicle's stability control system to stop the vehicle in a controlled fashion and in as short a distance as possible.

Stopping distance testing shows that most drivers without Brake Assist would stop a car from 60 mph in 239 feet. Cars with Mercedes-Benz Brake Assist stopped in just 131 feet. That is just about half the distance shorter!

When driving at highway speeds, it only takes 1/5 of a second to travel one car length. Even when drivers using brake assist applied the brakes very late in an emergency, the stopping distance was reduced by over a car length. One car length can mean the difference between just a fast heart rate and a serious crash.

Electronics can react faster than any human and during an emergency every little bit helps. Mercedes-Benz Brake Assist is that extra little bit of help.

So, is this system installed on a 2014 4Runner? Because my truck does this, but in my opinion it's entirely too sensitive. It has misinterpreted several quick stops and went completely overboard, causing everything to go flying. It was not called for. Are other people having this experience?

Am I missing something? What’s the original post have to do with 4th Gen 4Runners?

This happened to me for the first time (2019 TRD OR) a few weeks back. Scared the hell out of me and almost got me rear ended at highway speeds!

I thought for sure I had a malfunctioning brake system... but nope. It's a "feature".

Not saying it wouldn't save my butt some day... but clearly a bit too sensitive. In my situation I got cut off by a driver and switched to the brake pedal very quick with a bit of initial force (but didn't slam on the brakes). The 4runner took it from there... went from 60-20 in a split second and can't believe I didn't get rear ended!