Interesting observation about ABS and 02 WRX

I thought that was the main point of ABS brakes: controlled stops in circumstances like that. On dry or wet pavement, if anything I think it extends stopping distances, but I thought they would shorten in mixed conditions like what you describe.

The car did the proper thing.

Without antilock brakes, the result of what you did could have been a vicious spin to the right.

If the car spins, all bets are off. If it goes straight and hits something, at least the airbags and crumple zones will save your ass.

The main point is to retain control instead of spinning around.

This will most of the time increase stopping distances. ABS drivers need to learn "Steer your way out of it" on an unconscious level.

TBerk

Completely the opposite. ABS prevent detects incipient wheel lock-up and prevents it. This is to allow you to retain steering control. In slippery conditions it will, therefore, increase stopping distances. (Of course, in extreme slippery conditions you should hardly be using the brakes atall anyway .)

David Betts snipped-for-privacy@motorsport.org.uk

You describe a problem that many of us have experienced. The WRX has a bug in its ABS logic that causes what you describe. Subaru is in denial, probably because of the potential cost of a recall on all MY02 & MY03 WRX's. The problem has been resolved in the MY04.

Here's one of many links that document the problem:

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SNIP

Yes, when skidding is detected by the sensor, it transfers braking to other wheels. When all wheels detect skidding you are SOL when it comes to stopping.

My wife, traveling at 15 mph in our '95 Legacy wagon, began descent on a curved slight grade. After committing to the 100 yard stretch of heavily traveled roadway, she could see cars piled up, completely blocking the street near the bottom. With steep ditches on both sides, she assumed that she would be able to stop in time as the vehicles were still 50 yds away. Nope, she rode the brake all the way and piled into the others still traveling about 5 mph. If the brakes had locked-up all wheels, she could surely have stopped in that distance. Maybe in the ditch but probably no more expensive than the $4,000 she incurred. I really wish she had avoided the rear of the old jeep with the high mounted trailer hitch though.

That was the only time ABS came into play in 10 years and we are NOT real thrilled with them under 'those' conditions. SUVs with trailer hitches mounted higher than the average bumper height should have their insurance premiums automatically doubled. $4,000 damage at 5 mph, jeez.

BoB

Hi, She could pull the parking brake handle. ABS has it's short comings for sure. Pro drivers can do better with regular brakes. Tony

Not when it comes to avoiding accidents, no. It is not physically possible to cadence brake at the rate of abs. The whole point of abs is to allow you to steer round an obstruction whilst carrying out an emergency stop. 'Pro' drivers, of course, use abs for quite a different purpose - to allow them to brake to the maximum right to the apex whilst turning into a corner without wheel locking. (It is banned in most forms of circuit racing as a 'driver-aid'.)

There will, of course, be circumstances when you can stop quicker by locking the wheels to create a 'plough' effect in gravel or some types of snow. On ice or other very slippery surfaces, however, you're likely to slide just as far - or further - with the wheels locked.....plus you will be out of control.

At the end of the day, of course, if you activate the abs in normal road driving then you are braking too hard for the conditions anyway. Had the fun of glazed sheet ice on all the local side roads last week. Managed to stop for all the road junctions - including the downhill ones - without activating the abs once. It's simply a matter of planning further ahead and only caressing the brakes to take off that last two or three mph.

(As for our initial correspondent's suggestion that the brakes should work on one side and not the other when only one side is slippery...... how does a tank steer? )

David Betts snipped-for-privacy@motorsport.org.uk

She was so advised, but after-the-fact.

Her daughter-in-law had just slid into another Jeep when turning the last corner before they arrived at her home, so my wife was being as careful as possible. They had been downtown, inside the convention center, and was totally surprised to see 2"+ of un-predicted snow when they emerged to head home.

Several years ago, as she left for town, she did a 180 at the first intersection and returned home. We returned to the corner so I could show her how she 'should have handled it'. After doing the same damn thing, I got quite a ribbing as we returned home. It turned out to be deep ruts in the ice beneath the snow that was a real surprise when car pretty much followed the ruts regardless of attempt to steer.

Therefore, on her most recent encounter, I wasn't to critical about how 'I would have handled it'. :-)

BoB

Thanks for all the replies.

However, I have to say that I also think this is NOT normal behavior. Remember, In my circumstance the right side wheels were on totally dry payement and could have provide some braking assistance. I don't see how the car would have gone out of control while the right side wheels were still providing normal traction. Now, IF I said that the right side wheels were also detecting slipage, then I would agree that no traction should equal no braking and the car would have kept going at the same speed.

Can't wait for the next snow fall, I want to go out and try this experiment again in a safe parking lot. If anyone else get a chance to try it, please post your results to this NG for others.

Thanks again for everyones opinion.

This may be useful in traffic. But not so useful on narrow dirt roads with trees on both sides, when a herd of deer leaps in front of me.

I agree that it's a factor that experienced drivers must adapt to, and develop new skills to work around -- but I don't agree that it's an improvement.

Hi, BTW, do you have set of good winter tires on the car? My boy drives souped up Impreza RS, manual shift. I put on a set of Michelin Arctic Alpin for the season. He drives like ding bat but so far never lost control. If you pull ABS fuse, it'll be regular brake(?) My daughter drives same car with automatic shift with same winter tires. Goes skiing almost every week t the mountain, no problem so far. Tony

This is frequently a fairly hotly debated topic, both here and elsewhere on the Web. Those of us who aren't happy with the ABS performance on "non-standard" surfaces have found it beneficial to install a switch on the dash to disable the ABS function as needed. This takes about 1/2 hour to accomplish, and results in your ABS warning light illuminating when disabled, so you aren't likely to forget to turn 'em back on when you return to nice dry pavement. Instructions to perform this mod are available in various places on the Web, or feel free to contact me directly for the nfo.

ByeBye! S.

Steve Jernigan KG0MB Laboratory Manager Microelectronics Research University of Colorado (719) 262-3101

On Wed, 04 Feb 2004 15:54:48 -0700, S

My '89 GT wagon hasn't got ABS but I've been test driving a new Corolla out of curiosity to experience ABS before I get a new TS or WRX.

We drive on steep town hills and mountain roads on snow and ice about four months of the year here, and I've done some rally driving way back so I'm not a novice.

I love ABS - at least on the Corolla!

So far, when I have tested it on slick deserted roads or an empty parking lot I have found it gives me far more control than standard brakes, plus I have not detected any unexpected increase in stopping distance.

One of the best things about ABS is that one can test road traction at speed at any time safely by giving a quick jab at the brake to determine slipping point. With ABS that a far safer procedure than without.

Of course, if the surface is totally slick glare ice with no traction at all, then nothing would help except good ice studs.

So...is the Subaru ABS system somehow different or worse than Toyota?

might want to check this thread out:

It _is_ normal behaviour. You've no friction force acting on the left hand side of the car (it's on snow/ice). If the brakes on the right side were to be applied (such as would happen in a non-ABS equipped car), guess what would happen? The entire car would rotate clockwise (as viewed from above) about its center of mass. You'd now be getting T-boned by traffic approaching in the lane to your right.

Bottom line, you need to expect this behavior in an ABS-equipped car, and modify your driving style accordingly.

Agree with verbs. Someone else mentioned "how a tank steers" and that is how the original poster proposes ABS should work. If it did work that way, the result would have been like a tank steering...stop the right track, let left track continue rotating, ta-da! We have "pivot steer", where the tank turns on dime.

Actually, verb, the car would rotate somewhere between it's center of mass and point(s) of greatest friction--the two right wheels with dry- lane traction. Either way, bad business.

Steve

I noticed this in my car, too. When one side is on ice, the ABS tends to lift the brakes on all four wheels. This almost sent me rolling into an intersection once. Is it really supposed to do this?

I saw this demonstrated on a skid pad. One side was dry, the other hosed down with running water. With ABS, the car stopped straight ahead. Without, the car made a *vicious* spin. Made me a believer.