ABS: dangerous?

Question

I have a 2007 Toyota SUV. Often when I've had to hit the brakes hard ABS kicks in and the pedal does the familiar 'click click click' in rapid succession. The vehicle keeps skidding, however. This is my first concern - are anti-lock brakes really going to help me not hit the car in front of me better than regular brakes? In one case I skid, in the other case the brakes just keep engaging and disengaging. What's the difference?

Second, I hit a pothole today. Directly after the ABS was engaged for a second or two. I wasn't skidding. The pavement was dry and fine. But the "normal" brakes wouldn't work for a second after I hit the pothole. An unintended side-effect, I'm sure.

So is ABS dangerous?

Answer 1

From my personal experience, I can come up with only two cases when ABS is more dangerous than "no ABS":

1. Malfunctioning ABS that kicks in when not required. Some time ago I had a problem with ABS sensor due to which ABS occasionally engaged even on dry surface when it was not supposed to engage. The braking distance increased ~5x to what it used to be. As a temporary workaround I simply removed ABS fuse until I got ABS sensor replaced.
2. Thin layer of powder snow on icy surface. Some time ago I was driving in such conditions and there was a car in front of me and I had to stop as soon as possible. I pressed the brakes but the car just kept going forward due to ABS engaging. So I pulled hand-brake that blocked the wheels, the snow started to build up in front of the wheels and car immediately stopped.

Also, ABS is not supposed to decrease braking distance, but rather help you with maneuverability so that you could avoid hitting the obstacle.

In general terms, I would recommend you to think about braking in terms of kinetic energy conversion into heat energy. With ABS engaged, majority of that kinetic energy conversion into heat happens in "brake pads" and minority on "tire surface". If wheels lock-up completely, then majority of that energy is converted into heat on "tire surface" and minority in "brake pads". To stop your car as quickly as possible your goal would be to maximize energy conversion to heat in both places at the same time.

I would recommend you to check if your ABS is working properly, because, if it is engaging, when not supposed to, then you may not be able to stop in timely manner.

Answer 2

If your ABS is functioning properly. It is not dangerous. If you suspect a fault in your ABS system, best thing would be getting it checked. If it was dangerous, there would be opposition on putting it to every car sold today :)

About stopping distance. ABS can increase or decrease it based on surface you are driving on. But it will always improve steering control. See the wikipedia entry where this is explained : https://en.m.wikipedia.org/wiki/Anti-lock_braking_system

Answer 3

With rare and specific exceptions (usually related to the condition of the driving surface such as snow) correctly functioning ABS is not dangerous and occurances of circumstances where it is a help rather than a hinderance far outweigh those where the reverse is true. Modern ABS systems (pretty much anything from the last 20 years) are far better at maintaining the level of braking at an optimal level for balancing both minimising stopping distances and maintaing control and manuevering ability of the vehicle.

That said like any electrical or mechanical system ABS can go wrong and ensuring it is in proper working order is as important and ensuring that the rest of the braking system is functioning correctly.

If you are encountering ABS kicking in "often" then there is something wrong somewhere - I've been driving ABS equipped cars for over 15 years and hundreds of thousands of miles. And given that I'm just as dozy as everyone else I've had my fair share of hard braking moments yet I've only had ABS cut in less than a dozen times.

Hitting the pothole and ABS kicking in could be a momentary confusion of the system resulting from the differing wheelspeeds resulting from the pothole or it could indicate a malfunctioning sensor somewhere. Especially given you are seeing it rather alot in normal use. I'd be getting it checked for the peace of mind if nothing else.

Other things to consider that could be causing excessive occurances of ABS operating would be tires and driving style.

If your tires are of poor quality or excessively worn their grip levels could be significantly below what the car needs and it wouldn't take much for the brakes to overpower them and lock the wheels relatively easily under braking causing the ABS to try and compensate. As for driving style, I'm not trying to be offensive here but do you have a tendency to leave braking quite late? Are you frequently surprised by events ahead of you causing you to brake sharply?