Anti-Lock Brake question

ABS can't creat traction where none exists. On glare ice, ABS isn't going to help.

Ed

Very true on that but once the wheel stops spinning and becomes a plow, it has actually less tractive force. Guess the next time I drive in icy conditions, I'll just tread *much* more lightly on the brake. I got a bit cocky (always a dangerous thing) when I came up a long hill with no problems. In retrospect, the hill had been sanded and the sanding ended somewhat before my attempted turn. Oppie

It most certainly will helpl. ABS may not give you much more traction in that situation, but it will do a lot more for maintaining steering control than locking up the brakes would - and that's big in my book. I have ABS on both my SC & SC2, and have felt it in action quite a bit during WI winters for the last 12 years.

Oppie - it sounds like either of 2 things may have happened.

• The ABS engaged, but could not do much because of conditions, and the turning wheels didn't have enough traction on the ice to actually turn the car.

• The ABS did not engage due to a problem with the braking system.

Usually there is an audible sound when the ABS engages that most people with it have heard and should be able to recognize (I've heard people refer to it as 'marbles rolling around in a coffee can' or 'a slurping sound'. Did you hear it?

If you did not hear that sound, or the ABS or Brake idiot light came on, then there is likely a problem. Get it diagnosed and fixed, rather than compensating for it with behavior you'd use in a non-ABS car (pumping the pedal).

Good luck, Lane [ lane (at) evilplastic.com ]

I was more interested at the time in avoiding other cars than looking at my dash indicators . ABS definitely did not engage so I assumed that all wheels must have locked up and gave no velocity information to the controller. We are expecting more snow this week and I'll take the car to a parking lot and experiment a bit. The ABS/ traction control function perfectly on wet or uneven pavement where you get one or more wheels slipping. Just trying to learn capabilities. To quote Clint Eastwood in Dirty Harry, "A man's got to know his limitations."

Oppie

I live at the other end of the country, but we do have heavy rains and mud, causing the ABS to function. I often wondered if it would be effective to have one "aggressive tread" tire which might work as a baseline for the ABS under conditions like this. True, its not really practical, but just a thought ....

Interesting thought. The front tires should be matched so possibly on the rear put the odd tire. Would make tire rotation a bit confused though. I was thinking that they might eventually add a sonar/radar type doppler speed meter to detect actual vehicle speed. Would need ones front and rear that read out in two axes each to show when vehicle is skidding not just straight but at an angle (yaw). Is it worth the expense? Maybe on a high end vehicle with stability control but certainly not on any vehicle that I'll ever own.

Why go to that expense and complexity?

It would seem to me that the computer's program should be able to discern the difference between 4 wheels locked and sliding forward and a vehicle that is actually at rest. If the vehicle's speed is greater than some threshold, say 15MPH, and then within some time threshold, say less than

200ms, goes to zero, and if the brake pedal is depressed/engaged, then it should be fairly simple to assume the 4 wheel locked condition and activate the ABS.

Bob

You're a genius. Change in sensed wheel speed with respect to time above a threshold *would* be a good indicator of wheel lock. The threshold could be made adaptable by throwing in the acceleration sensed by the airbag controller. Don't know if the accelerometer output can be read by the ABS system in real time though. Oppie

Thanks for the title, but it just seems like the easiest way ... after all, to activate ABS, you would think there is already some type of connection to the Vehicle Speed Sensor output and a minimum speed threshold. Personally, I'd be surprised if they are not doing this already. You indicated you plan to test your system when you get some snow/ice, so let us know since it is possible that your vehicle is not working as designed.

It also might be some type of bug that you discovered in the program that is unique to that particular vehicle or year, make and model.

Bob