abs does not work in snow

[daveuj]

Hi can anyone please tell me if i am the only person to have a close shave (near crash) on fresh snow the abs did not seem to work,my dealer says that this is because all my wheels locked at the same time is this a known fault?.
Thanks Dave

 

[television]

Hello Dave and welcome to the forum, A hard question, I can always re call my ABS working well in the snow, and have never been asked this.

I would try the car again somewhere quiet, and try again on a wet road where you should feel the pedal pulsing under your foot.

Malcolm

 

[jberks]

abs is less effective in snow. It is possible for all 4 wheels to lock up at the same time if traction is particularly bad and/or you press the pedal too hard. In such cases, you simply release and reapply gently as if you had no abs.

When ABS was first introduced, Audi (if I remember right) used to install an off button as they felt that in snow, you were better off without it. Allowing the wheels to lock and a wedge of snow to build up in front of the tyres. Makes sense as if you have no traction to speak of, abs will have the brakes off more than they're on and it would be the same as not having the pedal pressed at all.

So, whether deliberate or not (I wouldn't put it past the boffins) if traction was so bad that all 4 wheels locked immediately, you were actually better off without it.

 

[kid-jensen]

Dave,

The ABS should definitely work in all slipery conditions, including snow.

What the dealer may be implying is that the car often stops better in snow if the wheels are locked, and the covering of snow is "scraped off" to reveal the road underneath.

This is the main occasion where ABS may be detrimental to your stopping distances.....but yes, you should hear/feel it pulsating....

 

[hawk20]

Dave,

The ABS should definitely work in all slipery conditions, including snow.

What the dealer may be implying is that the car often stops better in snow if the wheels are locked, and the covering of snow is "scraped off" to reveal the road underneath.

This is the main occasion where ABS may be detrimental to your stopping distances.....but yes, you should hear/feel it pulsating....

That is what I have always found and I had a fair amount of experience of snow in the Peak District way back when....

In my view, if all four wheels slip simultaneously, then the ABS should work on all four wheels at once. I would write to Mercedes and ask. Sounds wrong to me what happened to you.

 

[OmniCognateNeutronRangler]

ABS is non-existant in snow because there is absolultely no grip so it pretty much gives up. Having said that, if there's no grip then there is no grip irrespective of having ABS. The ABS can't invent grip if it's not there.

Yesterday there was sheet ice on the A34 after very VERY heavy falls of hail. It just hit the road and the cars/trucks turned it into sheet ice. My ABS was useless and the traction control had a hard time too.....which was fair as there was no traction to be had. All I could manage was 6mph. Felt sorry for the motorcyclist sitting on the side of the road!

BTW, 2 miles down the road there was no snow/ice at all. Odd.

 

[Hibbo]

That is what I have always found and I had a fair amount of experience of snow in the Peak District way back when....

In my view, if all four wheels slip simultaneously, then the ABS should work on all four wheels at once. I would write to Mercedes and ask. Sounds wrong to me what happened to you.

I think the ABS monitors DIFFERENCES between the wheels, if they are all the same then it thinks all is well. Although you would expect modern systems to be a bit smarter than that basic theory (all 4 wheels go from 40mph to zero in a split-second, hmmm something isn't right.....)

 

[television]

These system work on a variety of things. the ABS monitors the speed of the wheels and adjust the offending wheels accordingly, on newer cars this is done with the help of BAS thats brakes the wheels gently, should the vechile enter a back slide, then the slew monitor in the ESP takes over with the help of BAS to bring the vechile back into line.

Well thats what my mum told me to say. Malcolm

 

[hawk20]

ABS is non-existant in snow because there is absolultely no grip so it pretty much gives up. Having said that, if there's no grip then there is no grip irrespective of having ABS. The ABS can't invent grip if it's not there..

Logically, there is always some grip, however small. Let us be clear what we are saying. On black ice I find ABS causes the distinctive juddering and does eventually bring you to a halt. On snow, I have never put the brakes on and not had the distinctive juddering. And again in time you come to a stop. I assume the original thread posting is saying he put brakes on and got no juddering from ABS and just slid. I've never had that and if I did I would definitely suspect a fault.

 

[shadowninja]

I understand you're better off without ABS in the snow as it packs up snow in front of wheels rather than gripping and releasing which means you slide further.

Best way to check is to slam the brakes on and see if you skid or judder to a halt on dry tarmac.

 

[hawk20]

I understand you're better off without ABS in the snow as it packs up snow in front of wheels rather than gripping and releasing which means you slide further.

.

Yes, I've seen this said but never seen a proper test to prove it. IMO it depends on how thick, and how compressed the snow is; and what is under it. On packed snow, I find ABS first rate. And on snow with ice below it (wet road freezes, then snow falls), which is treacherous, ABS is a life saver.

But I can imagine on thick soft snow with no ice below it, no ABS might be good.

 

[whitenemesis]

Yes, I've seen this said but never seen a proper test to prove it. IMO it depends on how thick, and how compressed the snow is; and what is under it. On packed snow, I find ABS first rate. And on snow with ice below it (wet road freezes, then snow falls), which is treacherous, ABS is a life saver.

But I can imagine on thick soft snow with no ice below it, no ABS might be good.

Hedging yer bets there Hawk!

 

[hawk20]

Hedging yer bets there Hawk!

Yes I guess I am. I have found ABS so good in times past when it used to snow more often, that I find it hard to believe there are many situations where we are better off without it. Oh well time for bed!

 

[whitenemesis]

Yes I guess I am. I have found ABS so good in times past when it used to snow more often, that I find it hard to believe there are many situations where we are better off without it. Oh well time for bed!

G'nite mate... ABS + ESP has saved my bacon more than once....

 

[Shambolic]

Esp traction is causeing probs in the morning just now as still waiting on council fixing drain at top of hill from our house. Water runningoff hill and whole inside lane of dual carriageway covered in thick sheet ice.
Wife leaves in the morning and cant go anywhere as the engine cust power to rear wheels as they are constantly slipping.
This is on a main 70mph speed limit (A82) that you need to get out onto and get your speed up sharpish!!
Have phoned them again today to advise on problem as a serious accident looks inevitable!

 

[OmniCognateNeutronRangler]

Esp traction is causeing probs in the morning just now as still waiting on council fixing drain at top of hill from our house. Water runningoff hill and whole inside lane of dual carriageway covered in thick sheet ice.
Wife leaves in the morning and cant go anywhere as the engine cust power to rear wheels as they are constantly slipping.
This is on a main 70mph speed limit (A82) that you need to get out onto and get your speed up sharpish!!
Have phoned them again today to advise on problem as a serious accident looks inevitable!

Same problem I had on the A34 on Monday, although that was cuased by hail stones being flattened into the road by passing traffic. Like you say, could hardly get the car to go anywhere.

On the whole though ABS and ESP are a very very good invention. I still cadence break though, out of habbit. I find it very hard (mentally) to jump on the brakes and steer at the same time.

 

[wireman]

If the vehicle is traveling at a very low speed (or its wheels are turning at such a speed or less) the Anti skid baking systems designed by Bosch do not respond to locked wheel conditions. If they did the ABS (anti bascht system)would become active every time you tried to bring the car to a halt and it would not stop. I have read from bosch literature on ABS2 systems that the lower cut offf speed is 10Kph.
Anti skid brakes do not help in ice and snow conditions you need to cadence brake to stop in a hurry, just hit the pedal as hard as you can and then when the car starts to slide release it fully, wait for the car to rise on its springs and hit the brakes hard again as it starts to sink this will give better grip since the car falling onto its suspension will exert more down force and consequently increase the available grip.

Contrary to popular belief recent insurance data has shown that ABS equiped vehicles are more likely than non ABS vehicles to get involved in causing incidents where excess speed and close vehicle separation figure in the equation, The driver gets too cocky and over estimates both their ability to control the situation and their cars ability to take over when they cant cope anymore.

You can not go briskly in snow and ice conditions and still stop.

Do a skid training course they cost about £80 for an afternoons fun at dead low speed on a surface where you cant even stand up let alone walk.

 

[jberks]

Esp traction is causeing probs in the morning just now as still waiting on council fixing drain at top of hill from our house. Water runningoff hill and whole inside lane of dual carriageway covered in thick sheet ice.
Wife leaves in the morning and cant go anywhere as the engine cust power to rear wheels as they are constantly slipping.
This is on a main 70mph speed limit (A82) that you need to get out onto and get your speed up sharpish!!
Have phoned them again today to advise on problem as a serious accident looks inevitable!

The esp should still give you the best chance of getting it moving. Without it, you'll get a lot more noise but no more movement. In any case, she can always hit the 'off' button!

Having watched the esp kick in, totally unprompted, when driving over a flooded stretch of road, I'm a big fan!!

 

[OmniCognateNeutronRangler]

The esp should still give you the best chance of getting it moving. Without it, you'll get a lot more noise but no more movement. In any case, she can always hit the 'off' button!

the "off button" seems to be pretty much a waste of time to me. Even with the ESP turned off on my car it wont let me spin the wheels. If I try it still comes back on. Off should really just say reduced (and not by much)

 

[television]

You guy are wrong about ESP.

These system work on a variety of things. the ABS monitors the speed of the wheels and adjust the offending wheels accordingly, on newer cars this is done with the help of BAS thats brakes the wheels gently, should the car enters a back slide, then the slew monitor in the ESP takes over with the help of BAS to bring the car back into line.

As I said here there is a slew meter that monitors the slew rate of the car and has nothing to do with traction or any else like it.

Sorry to be picky

malcolm