Is ABS a good or bad thing if it gets really wintry?

[Mr2Mike]

jon- said:

The only negative experience I've had of ABS is in the older system which treat an axle as a whole (is this 2 channel?)

They can be lethal if, for example, your left wheel is on a big pile of wet leaves, but your right wheel has plenty of traction. It will still release the wheel with good traction, turning your car into a sled. I had this once in my MG ZR causing me to bump the car in front in the slowest crash I've ever been in. Apparently the VX220 system is the same?

The ABS system on my ZS180 was pretty poor as well. The worst trait was that once activated, it very often would not recover normal braking effort until you lifted and re-applied the brakes. That caused a couple of arse clenching moments until I learnt to simply not trust the ABS.

[andygo]

Mr2Mike said:

The ABS system on my ZS180 was pretty poor as well. The worst trait was that once activated, it very often would not recover normal braking effort until you lifted and re-applied the brakes. That caused a couple of arse clenching moments until I learnt to simply not trust the ABS.

I had that happen twice on the first gen Cossies I owned.

On both occasions I was approaching a 90 degree bend when one front wheel went over a smooth manhole cover. ABS cut in, pedal went down a long way. In both cases I hadn't planned for another 50 yds of room to slow down before the corner. Clearly I wasn't going as fast as I thought as I made the corner, but it was a foot off brake, wait a bit, press again moment.

It reminds me of an Ari Vatanen quote. Can't remember the question, but his answer was basically "Ven I think I need to brake, I count to three and THEN brake. It nearly always works"

The advanced driver tutor aksed me what I understood about the "3 second rule". He was very confused when I gave him Ari's reply...

[blueg33]

jon- said:

The only negative experience I've had of ABS is in the older system which treat an axle as a whole (is this 2 channel?)

They can be lethal if, for example, your left wheel is on a big pile of wet leaves, but your right wheel has plenty of traction. It will still release the wheel with good traction, turning your car into a sled. I had this once in my MG ZR causing me to bump the car in front in the slowest crash I've ever been in. Apparently the VX220 system is the same?

Isn't that what a diff does? Sends the drive to the wheel with the least grip?

[Ozzie Osmond]

I don't think you guys know what you are talking about. I've never heard of 2-channel ABS. I suspect you are getting confused with dual-circuit brakes.

• 4-channel ABS (normal today) involves independent braking of each wheel.

• 3-channel ABS (old-fashioned) typically had sensors on every wheel but only three separate brake circuits

1. Left front
2. Right front
3. Both rear wheels braked together


Leaving aside ABS, early cars had a single circuit braking system with one master cylinder activating all four wheel brakes when the pedal was pressed. Any loss of fluid resulted in total brake failure.

Later a master cylinder was devised with two separate chambers so that when you press the brake pedal you are effectively operating two master cylinders at once. These are typically plumbed so that one operates "front left and rear right" and the other operates "front right and rear left". If you get a leak in the system you should usually lose only half your brakes.

In all of this you need to bear in mind that rear brakes do much less work than the fronts, especially in small FWD cars which have very little weight at the rear. This is why the rear discs are typically smaller than the fronts and drum brakes were used on the back of some cars until quite recently.

Edited by Ozzie Osmond on Tuesday 8th January 14:18

[zebedee]

blueg33 said:

Isn't that what a diff does? Sends the drive to the wheel with the least grip?

we're talking on the brakes rather than under drive

[Zod]

HustleRussell said:

It's good if you accept and work around it's limitations. You still aren't just going to be able to mash the pedal and rely on it to stop you on sheet ice- you can almost invariably stop the car faster using cadence braking if you know how.

I'd like to see you cadence brake individual wheels.

[V8RX7]

Ari said:

ESP too, who the hell thinks they're so fking clever that they turn a safety aid like that off on public roads? Fine on a track where you've room to slide about and room to get it wrong, and the road surface and other drivers are consistent but on public roads?

I had a play in a snow covered car park in my wifes XC90.

I just booted it as I turned and the back came around as expected - what I didn't expect was the crappy ESP. I'm guessing it didn't expect me to correct the slide and I didn't expect it to (none of my cars have had it)

I found it terrifying that it didn't respond to my inputs and the car covered 3x the area of ground than would have been the case if I'd turned the system off.

I assume it's better if you do nothing or perhaps its another poor system as I'll admit an XC90 is hardly a drivers car.

[Super Slo Mo]

V8RX7 said:

Ari said:

ESP too, who the hell thinks they're so fking clever that they turn a safety aid like that off on public roads? Fine on a track where you've room to slide about and room to get it wrong, and the road surface and other drivers are consistent but on public roads?

I had a play in a snow covered car park in my wifes XC90.

I just booted it as I turned and the back came around as expected - what I didn't expect was the crappy ESP. I'm guessing it didn't expect me to correct the slide and I didn't expect it to (none of my cars have had it)

I found it terrifying that it didn't respond to my inputs and the car covered 3x the area of ground than would have been the case if I'd turned the system off.

I assume it's better if you do nothing or perhaps its another poor system as I'll admit an XC90 is hardly a drivers car.

I had a demonstration of Volvo's system about 6 years ago in a V70R driven by a racing driver on the wet handling circuit at MIRA.

It had 3 settings: FULL ESP, Part ESP (so allowed you to play a bit) and OFF.

First demo was with it off, circuit was soaking wet, 70 mph hand brake induced drifts into the corners, lots of sideways action, lots of amusement.

Second demo (I was a passenger, not watching from the sidelines), system set to FULL ESP. 70 mph handbrake induced slides, as before, but this time, the instant the handbrake was released, the ESP took over and put the car back into a normal attitude. It was incredible to see just how far out of shape the driver could get the car, and the system would still take over without drama, and put us back. Very reassuring for when you're pressing on on slippery back roads.

The third demo was on Partial ESP. This time, it'd allow the car to drift up to a point, enough to be entertaining, but not so far that we were entirely reliant on the driver's skills at not putting us off the track. Ideal for a novice, or, dare I say it, having a bit of fun on the road where the system will still ultimately intervene to stop things getting too extreme (I know, I know, we should save it for the track, but I reckon most of us have had a play on a wet roundabout when no-one's around).


On the other hand, I've driven other cars with ESP (my Skoda for one), where the system seems a bit slow witted and unresponsive. However, like ABS, it's handy to have in the background for those occasions where something unexpected happens, or there's a bit of diesel on the road mid-corner and you haven't spotted it. It might just be enough to keep you on the road one day.

[Ari]

Ok here's my little ESP story, for what its worth. My last eight (I think) cars have had ESP and I never trouble it because I drive within the cars limits on the road, and never take them on a track.

In April I bought an SLK 280 Sport, 231hp, big fat tyres, rear wheel drive. Love it. Since I'm not 18 any more I don't drive like a tosser, I just enjoy rapid refined easy comfortable trips in it. In fact I almost never use "sport" mode on the auto box, preferring to leave it in comfort (I use the paddles occasionally, normally to apply a little engine braking on long downhill sections). It's quite powerful enough not to need to slam down three gears every time its given a bit of throttle so "Comfort" works better for me.

Anyway, for some reason I decided to have a go at driving it in "Sport", which holds the gears and revs the car higher, plus kicks down sooner, just to see what it was like. It was dark, wet, cold, and I was on a dual carriageway approaching a roundabout and going straight on which led me to another dual carriageway.

So I'm in the outside lane as I approach, passing a couple of cars. Get to the roundabout, slow to about 10-15mph I suppose, nothing coming, give it a hard blip round the roundabout and straight on (its one of those places where numpties on the inside lane going straight on tend to "straightline" the roundabout, cutting up whoever is to their right so if I'm alongside someone I either blip ahead or back off in case they straightline. This time I opted to blip ahead).

Now I'd like to say there must have been spilled diesel on the roundabout, and there could have been. But more likely it was a case of too much throttle, sport mode meaning I was in a lower gear than I'd normally be/was used to, cold tyres, cold wet road, standing water, etc. I don't claim to be a Driving God, and us mortals occasionally make mistakes.

So across I go, left onto the roundabout then right to follow it round, boot full of throttle and wayhay, wasn't expecting that!!

Back end completely lets go and car starts to go sideways.

But here's the thing, before I could even think of giving it a "dab of oppo", holding the slide like a boss, and riding it out with a perfect blend of throttle and steering input, or possibly spinning 180 degrees and finding myself facing the car following me, or maybe T-boning the barrier that separates the two next sections of dual carriageway, the ESP kicked in.

And it was instant. It wasn't a case of it fighting me because it was doing its stuff the very moment the slide started, I hadn't had a chance to react (remember, this is real world totally unexpected, not "hooning" around a car park trying to provoke it and therefore being ready for it).

So, the moment the car let go it eased (not cut) the power, applied a touch of whatever corrective braking was required (back end going left so left front brake to stabilise I guess), neutralised the slide almost before it had begun and had me pointing back the way I was supposed to be going and power back on in probably under a second.

It was awesome. Like the hand of God had reached down and just tweaked the car straight.

And rather than, at the very least, the extreme embarrassment of spinning in front of a load of commuters on their way home, or at the worst, my beautiful Mercedes bent banana shaped around the end of the barrier, I carried on my journey.

And that's what ESP does. It won't overcome the laws of physics. If I had tried the same maneuver at 120mph I'd have crashed horribly ESP or no ESP.

But for situations where something totally unexpected happens right out of the blue, someone pulls out in front of you requiring a high speed swerve, unseen spilled diesel on the road, or some tt in a Mercedes playing with "Sport" mode and giving it too much throttle out of a wet roundabout, it is just brilliant.

And frankly I cannot understand anyone having it in their car and turning it off on public roads. Why would you, unless you'd overdosed on Top Gear and thought you were The Stig on The Track?

[HertsBiker]

ikarl said:

ABS is generally a good thing. Although you should be easily able to drive without it, people did for many years without dying at every opportunity

On the VX220 the ABS is pretty bad, so bad in fact that I fitted a switch to disable it (common mod) as when pulling up to a roundabout whilst braking you could easily trigger the ABS causing you to over-run you designated 'stop area'..... turning it off completely actually felt safer!

Really? My one never activated abs or locked up even under abusive conditions. How fast were you driving to have problems?

[HertsBiker]

ikarl said:

ABS is generally a good thing. Although you should be easily able to drive without it, people did for many years without dying at every opportunity

On the VX220 the ABS is pretty bad, so bad in fact that I fitted a switch to disable it (common mod) as when pulling up to a roundabout whilst braking you could easily trigger the ABS causing you to over-run you designated 'stop area'..... turning it off completely actually felt safer!

Really? My one never activated abs or locked up even under abusive conditions. How fast were you driving to have problems?

[fttm]

jon- said:

On the right kind of snow, locking the wheels can reduce your stopping distances. You'll still have no vehicle control though, which abs can sometimes help with.

I'd get it fixed for insurance reasons more than anything. I'm not speaking from any factual point of view, but I wonder how insurance / police would view an accident if you were knowingly driving with a faulty ABS sensor.

Erm NO ,the wheels have to be turning to slow you down on any type of snow and locking them will never reduce the stopping distance .
We have winter here (Western Canada)for 5 months and for most of that time the roads are pretty slick ,as a previous poster said if the ABS engages it's seen as a failure on the part of the driver but still glad it's fitted and working when some drastic avoidance tactics are called for .

[V8RX7]

fttm said:

Erm NO ,the wheels have to be turning to slow you down on any type of snow and locking them will never reduce the stopping distance .
We have winter here (Western Canada)for 5 months and for most of that time the roads are pretty slick ,as a previous poster said if the ABS engages it's seen as a failure on the part of the driver but still glad it's fitted and working when some drastic avoidance tactics are called for .

Our snow is somewhat shallower than yours and frequently locking the wheels pushes it out the way and enables you to contact the tarmac - so you are wrong.

[Super Slo Mo]

V8RX7 said:

fttm said:

Erm NO ,the wheels have to be turning to slow you down on any type of snow and locking them will never reduce the stopping distance .
We have winter here (Western Canada)for 5 months and for most of that time the roads are pretty slick ,as a previous poster said if the ABS engages it's seen as a failure on the part of the driver but still glad it's fitted and working when some drastic avoidance tactics are called for .

Our snow is somewhat shallower than yours and frequently locking the wheels pushes it out the way and enables you to contact the tarmac - so you are wrong.

The idea is that locking the wheels creates a 'wedge' of snow in front of the car, which gets more difficult to push as it gets bigger, thus slowing you down. In practice, perfect conditions like that are few and far between.

It's quite rare to get snow that works like that, more often than not it's either on top of compacted snow, or on frozen slush/ice, in which case, locking the wheels is still pretty useless.

You're right though, our snow is different. For the most part, our snow (that's in England, when we get it) is fairly 'wet', in that there's a good bit of liquid water between the snow, which lubricates it and makes it slippy. In places where it's properly cold, like Canada, the snow is fairly dry, and is a little more grippy as a consequence. These are all terms of relativity though, snow has little grip no matter how 'dry' it is.

[RacerMike]

Few things:

1. New MOT requires ABS/ESP to be working if it's fitted to the vehicle. No matter what age your car is, if the system has malfunctioned, strictly speaking, your car isn't roadworthy according to the MOT rules. Hence, if you have an accident and the Police/insurance company find out ABS was malfunctioning, good luck!

2. If it's just a wheelspeed sensor failure, you'll probably still have 'backup ABS' which means it will still do basic 'dumb' modulation.

3. ABS is better in almost all situations apart from the very rare occurances in deep snow. Even then, you lose directional control.

4. The nature of mainstream wheelspeed sensors means they're blind under about 5mph. Pulling off your drive and breaking would likely not see you exceed this speed, and hence the car doesn't know it's moving. This means you won't actually activate ABS and the wheels will lock 'as normal'.

5. Anyone who ever thinks they'd be better without ABS, try breaking with your right or left hand side wheels on ice and the others on tarmac. Let me know how many full 360 rotations you get before you come to a stop.

http://www.youtube.com/watch?v=g2EP4dmCpbk

6. By all means be a hero and drive without it, but ultimately, what's the point? Would you ride a motorbike with a cracked helmet or holed leathers? It's the same thing. Most of the time you won't crash and you'll be fine. But if you do, you won't....

Edited by RacerMike on Tuesday 8th January 20:30

[Ozzie Osmond]

V8RX7 said:

Our snow is somewhat shallower than yours and frequently locking the wheels pushes it out the way and enables you to contact the tarmac - so you are wrong.

One of the great PH myths is that ABS doesn't work and you're better without it.

If your ABS doesn't work it's because there's no grip. Your chances of encountering "special British snow" are about the same as your chances of "being thrown clear in an accident" if you're not wearing a seat belt.

[V8RX7]

Ozzie Osmond said:

V8RX7 said:

Our snow is somewhat shallower than yours and frequently locking the wheels pushes it out the way and enables you to contact the tarmac - so you are wrong.

One of the great PH myths is that ABS doesn't work and you're better without it.

If your ABS doesn't work it's because there's no grip. Your chances of encountering "special British snow" are about the same as your chances of "being thrown clear in an accident" if you're not wearing a seat belt.

Except I have EXPERIENCED it and on MORE than one occasion.

I have also seen my friend white as a sheet after his VX220T refused to brake on a track day.

THESE ARE NOT ONE OFF EXPERIENCES GOOGLE IT - WHY THE HELL WOULD WE MAKE IT UP ?

[TinyCappo]

Because this

[Super Slo Mo]

Just one thing to add, when ABS activates for a prolonged period, for example, on snow/ice/oil/diesel, the vacuum assistance that you normally get with the brakes gets used up very quickly and the pedal goes rock hard, and feels unresponsive, as if the brakes aren't working.

To combat this requires a lot of pedal pressure, that may be why some people are experiencing what they are describing as 'no braking', when in fact they need to massively increase their effort (and, in my experience, it is a relative massive effort, almost enough to require both feet on the brake pedal).

I don't know if the most modern cars with 'brake assist', are the same, I've not yet had the pleasure of using one under such circumstances.

[Tunku]

I think that most of you are missing the point that it's not the bloody brakes, it's the type of tyre you are using for the prevailing conditions. Most of you seem to have your fingers in your ears and going "lalalalalalalala"
PH really seems to be getting diluted these days.