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Snow, RWD car and ABS, I'm staying at home today!

carpmart - 5/1/09 at 05:44 AM

I got up for an early start but don't fancy driving 50 miles across Beds and Bucks with ABS and this much snow! Why can't we switch off abs in cars? Its bloody dangerous in this weather!

RWD is fun to a point but it just makes for a potentially fraught journey, especially if you get stuck half way up a hill as my 245 40 R18 don't lend themselves to being good snow tyres

Mr Whippy - 5/1/09 at 07:10 AM

why is ABS dangerous? beats thumping away at the brake pedal any day

sounds like you just need some more practice in the snow and RWD’s are ace for climbing hills when its slippy

rf900rush - 5/1/09 at 07:27 AM

Got a Subaru Outback 4x4 bus an a Ford Cmax
Guess what one the wife and kids want?

NS Dev - 5/1/09 at 07:51 AM

what???

What is the country coming to!

Its not like the snow is deep!!

RWD BMW 5 series on 235 low profile tyres and made it to work with only a few sideways moments.

If you are worried about driving in these conditions then you should get some training before driving a powerful locost!!!

blakep82 - 5/1/09 at 08:09 AM

eh? abs dangerous?

smart51 - 5/1/09 at 08:10 AM

quote:
Originally posted by carpmart
Why can't we switch off abs in cars? Its bloody dangerous in this weather!

You clearly don't understand ABS. Light snow and small patches of ice is IDEAL weather for ABS. ABS is better than you will ever be except in deep snow or very wet sand, where it is merely useful.

I wouldn't go out in this weather without ABS.

britishtrident - 5/1/09 at 08:12 AM

quote:
Originally posted by Mr Whippy
why is ABS dangerous? beats thumping away at the brake pedal any day

sounds like you just need some more practice in the snow and RWD’s are ace for climbing hills when its slippy

I suspect you haven't been driving long, If you try tapping or pulsing the brake on black ice ------ you will discover a great way to spin like a top. Only way to brake when it is really icy is really really gently.

Because of the very mild winters of the last decade and more a whole generation of drivers has grown up that has never driven in a real winter.

[Edited on 5/1/09 by britishtrident]

britishtrident - 5/1/09 at 08:21 AM

RWD is no problem give RWD any time over FWD --- ABS isn't exactly brillant at very slow speed or really slippery conditions, but you can still brake gently as you would without ABS. However when you get black ice you ideally want no ABS no brake servo and no PAS.

The other problem is most cars these days have tyres that are much too wide for snow, ice or torrential rain.

NS Dev - 5/1/09 at 08:21 AM

Agreed Mr Trident!

ABS or not, you can't really brake at all when its really icy so it makes no odds.

Use gears to slow down gently, then kerb or gutter or edge of verge to stop, only way on downhill when its too icy for the brakes to do anything.

Mr Whippy - 5/1/09 at 08:26 AM

quote:
Originally posted by britishtrident

quote:
Originally posted by Mr Whippy
why is ABS dangerous? beats thumping away at the brake pedal any day

sounds like you just need some more practice in the snow and RWD’s are ace for climbing hills when its slippy

I suspect you haven't been driving long, If you try tapping or pulsing the brake on black ice ------ you will discover a great way to spin like a top. Only way to brake when it is really icy is really really gently.

Because of the very mild winters of the last decade and more a whole generation of drivers has grown up that has never driven in a real winter.

[Edited on 5/1/09 by britishtrident]

hee hee na haven't been driving long at all....class

anyway when I was a bus driver they disabled the ABS on all the busses, even the new ones so the only way to not skid is to pump the pedal, driven bendy busses on black ice too, makes a car seem a total doddle

[Edited on 5/1/09 by Mr Whippy]

minitici - 5/1/09 at 09:14 AM

For old gits like me, brought up on ancient non-abs cars, ABS feels very strange when it cuts in.
First reaction is to take your foot off the brake as you thing the pedal has siezed
As a previous poster has said, on black ice, nothing is going to stop you short of aiming for a kerb.
Luckily my ABS is broken so my brakes feel normal and I feel that I have at least some control of my destiny

Mr Whippy - 5/1/09 at 09:31 AM

Hmm can’t say I’m all that convinced with ABS either tbh as its effectiveness seems to vary quite a lot, my SAAB took a scary amount of time to stop in the wet and I’m sure I could have brought it to a halt a lot faster than the ABS could but as it just kicks in the instant the wheels lock then you lose the chance to control anything or get any feeling for the road, my Volvo’s ABS was much better, the Vectra even better still but given the option I’d not have it fitted. Never used traction control but I’d just switch it off anyway, far to boring…

smart51 - 5/1/09 at 09:35 AM

quote:
Originally posted by NS Dev
ABS or not, you can't really brake at all when its really icy so it makes no odds.

Only if the entire road is completly covered in wet ice. Even then, the ABS will find the maximum brake force that can be applied and apply it.

On roads with patchy grip, the ABS will release the brake only on the wheel which is on ice. The other wheels with grip will continue to brake. When grip is restored to the slipping wheel, so will the braking effort. You just can't do that manually.

smart51 - 5/1/09 at 09:41 AM

quote:
Originally posted by minitici
my ABS is broken so ... I feel that I have at least some control of my destiny

That is exactly right. You feel that you are in control. In fact you are not, but you feel all nice. A well set up ABS system can control the brakes far more accurately and precisely than even an expert driver. Can you control the brakes of each wheel separately? Can you tell exactly how much each wheel is slipping?

There was a survey recently about driving. The question was “Do you think that your driving is better than average, about average or below average?” 80% of people rated themselves above average. The same applies to ABS. People think they are better.

[Edited on 5-1-2009 by smart51]

owelly - 5/1/09 at 09:46 AM

During the last bit of snow I proved that the hill desent control on my Range Rover is useless on ice! I stopped at the top of a hill, pressed the HDC button and took my feet off the pedals. I then wrestled the steering wheel as the car slowly started to spin and slide right to the bottom of the hill! I was glad to land in the ditch at the bottom! Throughout the slide, all four wheels were clicking away trying to stop them from spinning but as folks have said, if there is no grip, you've got no chance!

mr henderson - 5/1/09 at 09:48 AM

quote:
Originally posted by smart51

quote:
Originally posted by NS Dev
ABS or not, you can't really brake at all when its really icy so it makes no odds.

Only if the entire road is completly covered in wet ice. Even then, the ABS will find the maximum brake force that can be applied and apply it.

On roads with patchy grip, the ABS will release the brake only on the wheel which is on ice. The other wheels with grip will continue to brake. When grip is restored to the slipping wheel, so will the braking effort. You just can't do that manually.

Indeed.

carpmart - 5/1/09 at 09:55 AM

Interesting replies to this thread!

RWD - So, my experience and the reason for posting in the first place is that with big fat tyres which are legal but well worn, in a RWD car trying to hill start is pretty difficult! I live on the edge of the Chilterns, my route is back roads some of which are un treated. Its pretty slippy! This is my experience!

ABS - I find this pretty good in most situations except for snow with ice. My experience a couple of times with frozen road (snow on top) and with ABS is that snow builds in front of the front tyres and causes a snow plow type effect. There is no traction underneath the snow and a wedge building in front of the tyre. (this is exagerated further with fat tyres) If your going down hill at same time then its pretty lethal.

Finally, I have a little driving experience as I'm not the youngest forum member Put it this way, I was clearing my daughters car of snow this morning and she has been driving for a couple of years so at my age I have some practice in real weather! For my sins, I used to be a sales rep and covered 60k miles per year in the 80's early 90's. I drove RWD Sierra's and got a new one every 12 -14 months, so I have some practice in driving in all conditions. I also race a fireblade engined car with no differential so I'm pretty used to controlling RWD cars.

Anyway, as I said, there are some 'interesting' comments on the posts. All I will say is theory is one thing, how RWD and ABS works in the real world can be quite different.

Mr Whippy - 5/1/09 at 09:56 AM

just drive on the grass verge, it's much safer there and no slippy ice

Richard Quinn - 5/1/09 at 10:00 AM

I find my DTC and ABS excellent with patchy ice. Going back to rwd with a BMW tintop after years of FWD has been entertaining to say the least. All of my grassers etc have been RWD but driving sideways in 5 min bursts is not the same as a 50 mile commute. It's not difficult but I do find that I am far more alert to feelings and sensations when driving RWD and longer journeys in difficult conditions are a little more tiring as a result.

carpmart - 5/1/09 at 10:02 AM

quote:
Originally posted by Richard Quinn
I find my DTC and ABS excellent with patchy ice. Going back to rwd with a BMW tintop after years of FWD has been entertaining to say the least. All of my grassers etc have been RWD but driving sideways in 5 min bursts is not the same as a 50 mile commute. It's not difficult but I do find that I am far more alert to feelings and sensations when driving RWD and longer journeys in difficult conditions are a little more tiring as a result.

Very eloquently put!

This is exactly my experience with a big 5 series RWD BMW and fat tyres!

02GF74 - 5/1/09 at 10:12 AM

quote:
Originally posted by Mr Whippy
my SAAB took a scary amount of time to stop in the wet and I’m sure I could have brought it to a halt a lot faster than the ABS could but as it just kicks in the instant the wheels lock then you lose the chance to control anything or get any feeling for the road,

indeed; common misconception with ABS; it does not guarantee that stopping distance is shorter than with non-ABS brakes.

ABS = anti-lock braking system; purpose is to reduce the possibility of brake lock up and therefore provide a better chance of steering out of trouble.

likewise those who buy 4x4 think they can stop in shorter distance - but again that is a misconception - they usually don't because of 4x4 being generally heavier - and you just cannot argue with the laws of physics.

Mr Whippy - 5/1/09 at 11:07 AM

Worst I found was ABS on wet cobbles and the SAAB, it seemed that the system was getting confused with the pulsing amounts of grip and the time lag it took for the system to work. Basically it could not keep up, I could feel the car slow down till the ABS kicked in then suddenly it would practically turn the brakes off and I have to take my foot off the brake and try again, which was quite frightening really.

Benzine - 5/1/09 at 11:50 AM

I've been using the handbrake to go round corners this morning, awesome fun!

Phil.J - 5/1/09 at 11:54 AM

I have to agree with the original poster, ABS in snow can be very dangerous. I'm old enough to remember the ABS system being introduced by manufacturers, and they admitted at the time that snow was the one condition in which a conventionally braked car would out-perform an ABS equipped one.
It's not the slippery conditions, but drivers use the wedge of snow in front of the tyres to aid braking (ABS equipped cars ride over the wedge of snow).

[Edited on 5/1/09 by Phil.J]

britishtrident - 5/1/09 at 12:24 PM

A skilled driver using a conventional conventional braking system will stop in a shorter distance than ABS in all conditions --- in most conditions the distance just a couple of feet or so.

BUT the real advantage of ABS is that all but the biggest idiots (who are generally going much to fast for the conditions anyway) can panic stop and steer at the same time.

Where ABS has a problem is at slow speeds, ABS sensors are toothed rings which requires the wheel to rotate through given angle to provide the ABS computer with data, if you optimised the system for very low speeds it would require a greater number of finer teeth on the abs ring, this would impair the function at high speed and make this system more prone to failure.

The danger of running with the ABS fuse out is that most vehicles with ABS depend on the ABS to control the front/rear brake balance. Fine except for the fact many small FWD car are now grossly over brake on the rear. Put this together with the fact that most tin tops have grossly over servoed brakes and you get a potential for disaster. Nothing spins faster than a small hatch with the rear brakes locked --- no fun at 70+ on a wet motorway.

I think any insurance company examining a vehicle after an accident finding that the ABS fuse had been deliberately removed would have considerable justification for not paying out.

smart51 - 5/1/09 at 12:49 PM

quote:
Originally posted by britishtrident
A skilled driver using a conventional conventional braking system will stop in a shorter distance than ABS in all conditions --- in most conditions the distance just a couple of feet or so.

A very bold statement if I might say so. Your expert driver will have to adjust the brake force to maintain all the wheels just on the edge of locking without locking any of them. Perhaps on dry tarmac this could be possible.

quote:
Originally posted by britishtrident
The danger of running with the ABS fuse out is that most vehicles with ABS depend on the ABS to control the front/rear brake balance.

Not to mention the fact that many new cars use the ABS to measure the vehicle's speed. Unplug it and you lose the speedo.

NS Dev - 5/1/09 at 01:07 PM

quote:
Originally posted by carpmart
Interesting replies to this thread!

RWD - So, my experience and the reason for posting in the first place is that with big fat tyres which are legal but well worn, in a RWD car trying to hill start is pretty difficult! I live on the edge of the Chilterns, my route is back roads some of which are un treated. Its pretty slippy! This is my experience!

ABS - I find this pretty good in most situations except for snow with ice. My experience a couple of times with frozen road (snow on top) and with ABS is that snow builds in front of the front tyres and causes a snow plow type effect. There is no traction underneath the snow and a wedge building in front of the tyre. (this is exagerated further with fat tyres) If your going down hill at same time then its pretty lethal.

Finally, I have a little driving experience as I'm not the youngest forum member Put it this way, I was clearing my daughters car of snow this morning and she has been driving for a couple of years so at my age I have some practice in real weather! For my sins, I used to be a sales rep and covered 60k miles per year in the 80's early 90's. I drove RWD Sierra's and got a new one every 12 -14 months, so I have some practice in driving in all conditions. I also race a fireblade engined car with no differential so I'm pretty used to controlling RWD cars.

Anyway, as I said, there are some 'interesting' comments on the posts. All I will say is theory is one thing, how RWD and ABS works in the real world can be quite different.

Must admit, I wouldn't want to have been driving my Locost this morning!!!

hellbent345 - 5/1/09 at 01:38 PM

quote:
Originally posted by smart51

quote:
Originally posted by britishtrident
A skilled driver using a conventional conventional braking system will stop in a shorter distance than ABS in all conditions --- in most conditions the distance just a couple of feet or so.

A very bold statement if I might say so. Your expert driver will have to adjust the brake force to maintain all the wheels just on the edge of locking without locking any of them. Perhaps on dry tarmac this could be possible.

i was under the impression that it just turned the braking force on and off to the wheel allowing it to unlock, rather than actually applying the maximum possible braking force with the available traction, so a skilled driver could 'feel' the edge of traction, whereas the computer would turn the brakes off and on at presumably maximum pressure (as we are told with abs to squeeze that brake pedal hard and not worry about trying to feel grip etc) - quick cadence braking certainly but not as good as the feeling of the grip... certainly abs is of great use in all road conditions with inexperienced drivers, whos first and only thought is to push the brake pedal hard to the floor and keep it there - they have been conditioned with their normal driving that the harder you squeeze the pedal the more you brake, and its hard to get out of this subconscious thought pattern if you havent had an amount of training. snow and abs is bad its basically just turns braking off altogether, whereas with normal systems there is a limited snow wedge effect - this doesnt happen in icy conditions or anywhere else so anybody other than really expert drivers is probably going to be better of in an abs car.

[Edited on 5/1/09 by hellbent345]

Dingz - 5/1/09 at 01:53 PM

Only drove across Bedford this morning in the robin Hood, worse bits were my road and the industrial estate was great fun!

smart51 - 5/1/09 at 02:21 PM

quote:
Originally posted by hellbent345
i was under the impression that it just turned the braking force on and off to the wheel allowing it to unlock, rather than actually applying the maximum possible braking force with the available traction

Perhaps a few decades ago. These days, ABS detects the rate of wheel deceleration and drops the pressure by enough to release the wheel. Once the wheel speed has recovered, it then adds pressure in small pulses watching the wheel speed all the time. If the wheel starts to lock, it backs off the pressure a little, waits for the speed to stabilise and adds more pressure little by little. It is always trying to keep the wheel turning, rather than skidding, but trying to keep as much brake force on the wheel as possible for the given amount of grip.

Our ABS systems are for vehicles with air brakes. They estimate the grip on the road and the load on the vehicle to decide how big the pulses should be when reapplying the brakes. Too big and the wheel just locks up again, too small and it takes too long to build the pressure back up. Its pretty sophisticated stuff these days.

carpmart - 5/1/09 at 03:47 PM

Thanks all - Lots of 'interesting' comments and overall I thought it was an interesting topic of conversation!

Liam - 5/1/09 at 05:59 PM

quote:
Originally posted by carpmart
Thanks all - Lots of 'interesting' comments and overall I thought it was an interesting topic of conversation!

Well said! I'm just gutted that I'm currently using a FWD vectra instead of my usual 3 litre omega! Driving to work (in Bedfordshire, too) would have been fun this morning in the meggy

edit: Which reminds me - when I was drifting/sliding to work in last year's snow, I couldn't help but chuckle as I drove past a brand new Audi A6 quattro in the ditch with Mr Rep standing along side in his suit with a puzzled look on his face. Almost stopped to explain to him 4WD doesn't give you more grip, but i think it would have been lost on him

[Edited on 5/1/09 by Liam]

Dingz - 5/1/09 at 11:04 PM

quote:

Only drove across Bedford this morning in the robin Hood, worse bits were my road and the industrial estate was great fun!

More of a problem trying to get out of the car park this evening though as it is up a slight slope and it was very icy, just sat in second gear not going anywhere! eventually made it.

David Jenkins - 6/1/09 at 09:10 AM

Liked a clip on the news last night, showing the chaos caused by 20mm of snow... a large 4x4 going slowly down a hill, clear road in front of him/her, losing traction and going into the bank - at about 5 mph. Clearly has never been taught how to use all that wonderful technology to get down a slippery slope without incident! (hint - engage low ratio gears, keep your foot off the brake).

[Edited on 6/1/09 by David Jenkins]