Safe Speed Forums

Yes, it was a straight line head-on crash but your post was about ABS and my reply was regarding your post on ABS.

PeterE, was there enough room to drive onto the hard shoulder of the road and around the van?

If there was and PeterE had ABS he could possibly have steered the car onto the shoulder while still braking to optimum effect. Without ABS any option other than a head-on is unlikely unless the driver had enough advanced driving experience to threshold brake and turn. The latter is highly unlikely in an emergency situation for the vast majority of the population.

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Ross

Yes I'm a hoon, but only on the track!!!!

It wasn't me in the crash, it was someone I know. It was on a single-carriageway road in Cumbria and I suspect there wasn't room to the left to avoid the van, even if there had been enough time to do so.

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"Show me someone who says that they have never exceeded a speed limit, and I'll show you a liar, or a menace." (Austin Williams - Director, Transport Research Group)

Any views expressed in this post are personal opinions and may not represent the views of Safe Speed

PeterE, I was not meaning to suggest that the driver of the car was in any way responsible, simply that if there was an exit the only way to take advantage of it would be if the car had ABS or the driver was prepared to drive onto the hard shoulder without braking, not a really good idea.

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Ross

Yes I'm a hoon, but only on the track!!!!

At no time do you ever want a 44 ton trailer to lock its wheels, the trailer only has one place to go, out of control side ways, ABS on trucks is a must have.

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Steve

I'm sorry bmwk12 but Oscar is 100% correct about loose surfaces and ABS.

Absolutely anyone who knows anything about ABS on gravel and snow will tell you that ABS is about the most dangerous thing around. Without ABS the wheel will lock and the tyre will push through the loose stuff down to the hard layer below. In the process a wall of gravel/snow builds in front of the locked tyre assisting in the generation of friction thus assisting to slow the car down even more.

With ABS a car will virtually not slow down at all as the ABS detects that the wheel is constantly locking. If you are approaching a corner too fast there is not point in ABS assisting steering as the car will simply slide off the road no matter what you do with the steering wheel.

For anyone who travels on both surfaces a switchable ABS system is the ONLY way to go. Otherwise I'd leave if off permanently as it is far more dangerous to drive on gravel WITH ABS than to drive on bitumen WITHOUT ABS.

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Ross

Yes I'm a hoon, but only on the track!!!!

Always felt much safer without ABS, much more in control. The only time in 40 years when a trailer went sideways on me was when the yellow brake line burst as I did a quick stop as an old gent ran out in front of my truck (30-odd years ago. Plastics are better quality now!). Tractor braked, trailer tried to overtake me! Fortunately, no damage or injuries.


BTW, my original post about ABS was taken from one web-site and was the general consensus of opinion of all the sites I read!

You are incorrect, a locked wheel on loose gravel is sliding on top of the surface. ABS does not allow the wheel to lock.




Wheels braking will push through to the harder layer, non ABS will spend more time sliding above it. The moment the vehicle loses friction it slides and loses braking effectivness.

ABS maintains the highest amount of friction between tyre & surface, as it prevents the wheels losing friction and sliding.

The moment the wheels lock and slide, friction is lost.



ABS or non ABS is not the point here, you should check and adjust your speed prior to the corner. I would prefer ABS in any cornering situaction, than the total loss of control of a vehicle in a skid.



ABS is a dedicated brake system, that cannot be switched off, you seem to be confusing ABS with traction control.

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Steve

See this chart:



Typical friction characteristics: (a) dry asphalt; (b) wet asphalt; (c) gravel; and (d) packed snow.

From page:
http://www.safespeed.org.uk/braking.html

You can see that locked wheels offer far superior braking effect on gravel. ABS limits slip to about 5 to 15% depending on the system.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Please supply data, that produced the chart.

Vehicle Used, overall stopping distance with & without ABS.

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Steve

bmwk12:- So you know better than all the experts and manufacturers of ABS, do you? Or is it just your opinion? I culled my info. from websites of experts and funnily enough, they coincide with my own experiences; or are you just trolling?

As ever with Safe Speed data, if you follow the link provided the full source report is there (link under the chart). In this case it's a comprehensive technical analysis of "grip" and braking.

I don't imagine for a second that it's based on a single vehicle test, and the characteristics shown in the chart are well known.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Did you not understand the chart? It plots slip against friction so therefore it covers vehicles both with and without ABS - simply choose the degree of slip the system permits and plot a vertical line up the chart to see what percentage of grip this equates to. As everyone has already said, on asphalt ABS compromises a little grip in order to improve control. On gravel it compromises a lot, indeed it can compromise so much that you actually end up with less control!

I'm involved in rallying, a sport in which ABS is considered an absolute no-no. The general principles of achieving maximum braking were once explained quite succinctly to me as...

On tarmac the tyres should be squealing but still turning,
On gravel or loose snow the tyres should be ploughing
On packed snow and ice it won't make a lot of difference what you do, so concentrate on retaining control and steering where you want to go!

The really telling part of the chart is where curves "b" and "c" actually intersect. Yes, that's right, you can stop quicker on gravel than you can on wet tarmac as long as you lock the wheels!

(It would be interesting to see the original test data that created those charts, and in particular what tyres were used for which surfaces)

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ABS is an electronic device and therefore requires power to operate. On most cars with ABS you simply remove the fuse and the ABS stops working. I have done several BMW driving courses and the guys simply remove the fuse to enable the car to lock the wheels in some exercises.

If the ABS can be turned off with a fuse then the fuse can be replaced with a switch.

As an ex motor mechanic I happen to understand a few things about how a car works and this is one of them!

Have you got the message yet that ABS is NOT a good thing on loose surfaces? Why do you think that the WRC cars do not have, and have never had, ABS? Most other forms of motor sport use ABS if it is legal for their category.

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Ross

Yes I'm a hoon, but only on the track!!!!

(Audis always used to have switchable ABS - not sure if they still do...)

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CSCP Latin for beginners...
Ticketo ergo sum : I scam therefore I am!

ABS is more than an electronic device, by removing the fuse, you are turning off the sensor's, you are also taking the electrics away from the control pump.

As ABS systems become more and more complicated, and more controlled by electonics, i really would suggest, that you do not give out such poor advice.

Should anyone want to turn their ABS off, they really should talk to their main dealer mechanic, to find out exacley what else that fuse will effect.


Have you got the message yet that ABS is NOT a good thing on loose surfaces?

Based on what information



Lets look at the most advanced race car, an F1

Both braking & Traction is full electronically controlled.

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Steve

Time for me to join in.

I would argue that F1 cars race on lovely smooth tarmac and rally cars are just as advanced just in different ways. Rally cars are also deisgned to run on almost every type of surface known.
Do you really think that if ABS was better on loose surfaces they would not use it?
I think by the example that Rally cars do not use ABS proves the case that ABS is not better than locked brakes on gravel and other similar surfaces!!

Just my 10 cents

ABS is banned in Formula 1. That's why they lock up the wheels occasionally. However, the drivers are so good that in a 200 mile race, the average driver won't lock a wheel, despite braking from 200 to 60 in 80 metres.

They do have traction control for acceleration, as this allows the driver to bury his foot coming out of the corner without having to worry about the back end stepping out. Many fans of the sport are against the TC, though, as it makes an absolutely horrible sound as the car exits the corner (the fuel supply is completely cut for that revolution of the engine, but then is back on full the next revolution, so the engine sounds like its dying..)

Edit: Also, F1 drivers don't brake by locking their wheels, even on slippery tarmac, because the disadvantages (having to do another 30 laps with flatspotted tyres) outweigh any advantages (shorter braking distance - possibly..)

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-mike[F]
Caught in the rush of the crowd, lost in a wall of sound..

Yep. And the flatspots would be HUGE. The rubber is very soft!

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Indeed - supposedly locking a wheel once can then produce a vibration that stays with them until the next pit stop. Not much fun when you're already in a less than luxuriously comfortable environment..!

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-mike[F]
Caught in the rush of the crowd, lost in a wall of sound..

Well, having done it in a kart during a race I can tell you that even with those dinky little wheels, the vibration can be enough to loosten your fillings