I have a 2022 Subaru Outback, the replacement for my previous 18-year-old Subaru Forester. Now I am mostly comfortable with all the new technology in the car, but what still makes me a little uncomfortable is not having a manual back up brake for the electronic braking system. Usually I think about this as I am driving down a very long hill on the highway. How exactly does electronic braking work and why is it okay to make the car without a manual emergency brake lever? Thank you. - An de H
Electronic braking in general is an expansive subject, but I believe you are inquiring specifically about your electronic parking brake (EPB) system. Firstly, an EPB features a small electronic servo motor typically built into each rear caliper controlled electronically. This system does away with the cables and levers located in the cabin and under the car. It is replaced with a simple switch typically located in your center console, control module and caliper servo motors.
Like it or not, in the name of safety and convenience most manufacturers want to control more of your driving experience. Hence, they are moving away from the manual, old school cable actuated systems in favour of an EPB for many reasons.
A few of those reasons include the automatic activation of the EPB under differing circumstances. A few such EPB automatic activation reasons include when parking on a hill or when the driver’s door opens under motion, or when a seat belt is unbuckled. In some instances, the EPB can work in conjunction with the emergency braking system when a panic stop situation is happening. Hill start assist systems are also related to the EPB. Every manufacturer uses slightly differing reasons to employ the EPB.
Are there disadvantages? Of course. It’s a complex system, which means its potentially costly to repair as well as the EPB sometimes being stuck on when your battery dies. That being said, most manufacturers still believe that the benefits outweigh the negatives.
While I am still on the fence with the idea of why we actually need so much driver assistance, I believe that we don’t require a manual emergency brake system. A manually activated emergency back-up brake system was usable decades ago when brakes were a single circuit fluid system. In this ancient system if you sprung a brake fluid leak all the fluid quickly depleted itself resulting in no brake action whatsoever. In this case a manual emergency brake was better than nothing.
This system went out in the 1960s and 70s and was replaced with a dual diagonal braking system. This newer system sees the left front and right rear hydraulically coupled together as well as the right front and left rear connected together. This contemporary system has little to no hydraulic connection between these two diagonal systems. So, if you spring a leak, you will lose braking in the two diagonally connected wheels only.
As most of you know, the majority of braking in any vehicle is done by the front brakes. Even if the system is limited to only one front and one rear brake, this still offers far better stopping potential to the driver than them trying to manually engage the two rear wheels only. Almost all brake loss conditions are from fluid leaks under the car. Even the brake master cylinder employs dual circuits making the whole manual emergency brake system in my opinion redundant.
Lou Trottier is owner-operator of All About Imports in Mississauga. Have a question about maintenance and repair? E-mail globedrive@globeandmail.com, placing “Lou’s Garage” in the subject line.
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