Checking ABS - Brian
Not being in the habit if locking up the wheels when braking I took advantage of the snow yesterday to try out the ABS in Sainsbury's carpark.
The wheels locked up alright, I steered right - and went straight on.

Does the ABS not work at low speed (about 10 mph) or is it faulty?
What types of fault are likely?
The only time I have emergency stopped recently was about 6 months ago when a couple of escaped dogs ran out in front of me on a dual carriageway, but that was in a straight line.
Re: Checking ABS - richard price
have a look in the manual, my car's abs does not operate below 10mph.
Re: Correct ABS Operation - Tomo
An ICY road is better to try out the ABS (and a bit of speed as suggested above. It is worth a try, because the car may steer but it's not like ordinary steering.

Only don't steer into anything!
Correct ABS Operation - David Lacey
For ABS to work correctly, you (i) need to be travelling >8mph (IIRC) & (ii) there needs to be some grip on the road surface. With snow, there is next to none.

This is the problem with ABS - people wrongly assume it is infaliable and WILL get them out sticky situations.

Unfortunately, it doesn't work like that!


Re: Correct ABS Operation - Andy P
I've read that in snow, ABS isn't any use anyway. From what I can remember, a car will stop quicker if the wheels are locked, building up snow in front of them and helping the car to stop.

Re: Checking ABS - Jud
The Primera abs works at working speeds cant give you a speed usually when it cuts in i'm too busy controlling the car to check instruments. The first primera i had (1992) had a four channel system and when it worked would physically push up the brake pedal in a pulsating manner.
Primera 2 was again a four channel system but the abs cut in much quicker and the pedal pulsating was at a higher frequency.
Early ford Mondeo's only had a two channel system and i actually had to doo an emergency stop with one , the wheels locked up. Beware of cut price ABS systems.
Re: Checking ABS - PhiL P
I recall a few years back some Audis used to feature a button on the dash so that you could switch off the ABS for snowy conditions.
Re: Checking ABS - Julian Lindley

Your ABS is fine.

The principal of the system is to stop individual wheels from locking up under brakeing loads. In order for the car to be able to maintain steering, some grip between tyre and road is essential, and in addition, this will also be influenced by the velocity and weight/weight distribution of the car.

Like most electronic systems ABS is dumb; You the driver have to add the additional inputs, and moderate your driving style accordingly.


Re: Checking ABS - CJ Lovett
If all four wheels lock together (as on an icy patch of whole car area) the ABS has no reference to work with. It relies on a differential speed between wheels via the cogged sensors to inform the ECU, which then "modulates the brakes, keeping the wheels turnong, hopefully on the point of locking.
Re: Checking ABS - John
Does anyone else get just a mite annoyed when Mr Ripley repeatedly states that ABS doesn't cut braking distances ? For highly experienced drivers who have the opportunity to practice regularly maybe not, but for mere mortals.... I've had mine cut in on rare occasions (pedestrian trying to kill herself) and was mighty glad of it. The lack of drama is astonishing.

Keep up the good work Paul - but drop the ABS bit.

Stopping distances with ABS - John S

Is the problem that PR perhaps doesn't always explain it very well? Compared to locking the wheels and sliding, ABS does cut the braking distance, but the point he's making is that if the road is slippery all ABS can do is minimise the distance needed to stop and allow some degree of control - but it will still take longer to stop than on a dry road. Plus, the stopping distance on a dry road is still the same.

I'd agree with you that, as in the case of your pedestrian, the big benefit is that all you need to do is hit the brakes hard and let the electronics take care of the clever bits. In these circumstances, ABS probably does a better job than even a skilled driver. I don't believe many can pump the brakes 10 times a second, and modern ABS only operates on the wheels that are locked.

The targets of PR's comments are those drivers think that ABS can defy the laws of physics and allow them to drive in the same manner in all weathers, or drive up the exhaust of the car in front, because ABS will magically bring their car to a halt in no distance in all weathers. The fact this isn't the case is always explained in the Instruction Book, but the ones that don't read that probably don't read Paul Ripley either!


Re: Stopping distances with ABS - Stuart B
John S wrote:
> Is the problem that PR perhaps doesn't always explain it very
> well?

John, I know I have had a snipe or two at PR in the past, probably undeserved snipes being totally honest.

I wonder if PR explains it clearly but the explanation suffers at the hands of the sub editors. Remember the occasions when HJ has set the record straight after some of the dog's breakfasts they have made of his offerings.

Happy hols,
Re: Stopping distances with ABS - John S

Yes, that could be the problem. HJ certainly has been unreliably edited in the past. Don't really like to take issue with PR, as he talks a good deal of sense. I just wonder if on many occasions he's preaching to the converted - not his fault of course - there are those who know it all!

Compliments of the season


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