Anti-lock brakes

[dpnguyen]

I was playing around in the snow today. When DSC kicks in, the DSC symbol flickers to tell you it's working. I noticed that there is no ABS light that flickers when the ABS kicks in. I know it was working because I could feel the pulsation from the brakes. Is this normal on an '03 325i?

 

[epj3]

Yes, for that exact reason -- you can tell when the ABS kicks in, but you really can not tell when the DSC turns on.

 

[epj3]

I do have to mention that our pontaic minivan does have a low traction light that comes on with the ABS -- as if you couldn't figure it out by the VERY audible pinging.

 

[MrElussive]

DSC works with the ABS to slow your ass down, which is why the light comes on when you're slipping. ABS is always working and is part of the brake system and uses its own sensors...ABS and DSC work together, but only DSC lets you know that it's working with a light...ABS pulsates at the brake pedal when it's doing its thing.

 

[codex57]

Yup, you're fine. I have an 03 325 and it's supposed to work that way.

 

[aNoodle]

Yep...that annoying Woody Wood Pecker pulsation is exactly what ABS is supposed to do. It rapidly slaps the pads against the rotors so amazingly fast so that it achieves the maximum friction without letting the wheel ever lock.

I could go looking for the article…but trust me I'm not selling anything…the National Highway whatever administration recently finished a study of ABS. Anti-lock had been praised as the next coming as far as automotive safety deals go. But the study found that most drivers, when they felt the sensation through the break pedal, actually lifted their foot off the brake!!!!!

As a result, ABS has had a negligible impact on reducing crashes cuz people don't know how to use them. We used to be taught to pump the breaks so they don't lock. I was told to not try any excessive steering maneuvers while braking hard. But with ABS, we're supposed to slam down hard and stay there and continue to steer. (Roundel had a good article on this...telling people to go out to their local empty parking lot and practice a few emergency stops.)

Good think you got a chance to feel how it is so when you really need it, you're not one of these statistics that lifts off the brake in a knee-jerk reaction.

 

[Chakueem]

So ABS basically takes applying the brakes when braking hard. If I were trying to avoid hitting say a deer in the road and I slammed on the brakes, I should hold the pedal all the way down and let ABS take over slowing the car as quickly and safely as possible?

 

[snowcrash]

Yup hold down the brake and continue to steer in the direction you want to go. It'll slow you down as quick as possible w/o causing a skid.

 

[epj3]

Chakueem -- on BMW's you do want to slam on the brakes and let the car stop itself. I do know that on the GM's we've owned, that on dry conditions you would stop much faster if you slammed on the brakes, let go and pressed it again. The bmw is a little bit more refined.

 

[codex57]

Anti-lock brakes are supposed to relieve you from having to pump the brakes to avoid locking them and skidding. It pumps the brakes for you, and at a much faster rate than you physically can. This allows you to steer around an obstacle if necessary because the brakes won't lock. When your brakes lock, you skid and just continue in the direction you were heading. If there's a rock or kid or whatever in your way, you're gonna hit it.

So on your BMW, just slam on your brakes and steer around if necessary.