Safe Speed Forums

it will be interesting after this winter of unusually high number of frosts/ icy roads to compare the number of "skidding accidents" from esp to non esp vehicles, although I realise that this information probably won't be collated. ESP is a good thing as long as drivers of ESP vehicles realise that the ESP won't do EVERYTHING for them. The art of car control is knowing what to do in a skid and having experienced several skids you will after a while get a "feel" for correcting it without panicking, over reacting etc. But you do need to know what to do. If everyone who buys an ESP vehicle doesn't know how to correct a skid with the steering wheel will they assume that they don't have to give any input at all?

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My views do not represent Safespeed but those of a driver who has driven for 39 yrs, in all conditions, at all times of the day & night on every type of road and covered well over a million miles, so knows a bit about what makes for safety on the road,what is really dangerous and needs to be observed when driving and quite frankly, the speedo is way down on my list of things to observe to negotiate Britain's roads safely, but I don't expect some fool who sits behind a desk all day to appreciate that.

all ABS will be monitoring wheelspeeds, these days at all 4 wheels, and reducing the pressure independantly in response to slip.
more advanced systems in vans may well use a load sensor (usually averaged rear axle ride height) to adjust thresholds more appropriately.. some systems have been doing the same with steering angle for a while too (kind of a poor man's ESP).

the basics of good ABS control are pretty much a mature technology, the various suppliers do like to claim new features with their confusopoly of TLAs to get the edge on each other and maybe allow them to quote a few fractions of % stopping distance.



as mentioned elsewhere on the thread, the setup of the system will be pretty much specified with the vehicle manufacturer to fit their required brand ID or such.... some are very authoritarian and others alot looser.
as for hearing or feeling the intervention, they are getting alot more refined on both counts so the flashing light may be the only hint you get! (aside from however much over/under steer its setup to allow)

Love it!
I was on a muddy cart track a while ago (long story...) and noticed what I thought was a hint of a misfire. The car felt otherwise quite normal - though a yellow light on the dash (which I now know was VSA cutting in) was flashing like a loose connection at me. I tentatively pressed the disengage VSA button and was fighting the wheel in all directions to stay on track. I soon put it back on again!

ESP requires brake intervention (and throttle intervention) and so requires traction. Therefore I doubt that ESP was a significant factor for Squirrel since there is practically zero traction on ice, rather ESP tried and failed and Squirrels steering was the deciding factor until the car regained grip. Also, like ABS, ESP does not function a low speeds. [don’t know exactly what the minimum speed is but I would imagine that 15mph is considered sufficiently slow not to require ESP]. Also, ESP tries to sent the car in the direction of the steering wheel, so when Squirrel was on opposite-lock, that’s where ESP will send the car if it can.

I think Squirrel is actually singing the praises of ESP at the expense of his own skill.

ESP and opposite lock are in conflict, because when you steer into the slide, ESP calculates that you are going where the steering wheel points and so does not intervene. Some people say that because of this you should not steer into a slide. This is utter rubbish as once you are sliding, (beyond ESP’s abilities) and you are down to your own ability.

If you go into a side ways slide, do not ‘wait’ for ESP to rescue you – ESP has been trying and failed! People describe ESP ‘coming to the rescue’ when in fact the car has recovered due to loss of speed, turning or passing onto better traction.

ESP CAN NOT DEFY THE LAWS OF PHYSICS, it can just take you closer to the limits without you realising it!

Quickly touching ABS and stopping distances. At best it reduces them by 10% but in some conditions increases them – particularly dry roads! It may be of interest to some people that if in an accident, you are more likely to be killed in a car with ABS than without! [This statistic has nothing to do with the fact that there are more ABS cars on the road – it means take 100 ABS accidents and 100 Non-ABS accident, (which will be harder to find as there are less non-ABS cars about), then the fatality rate will be higher in the ABS cars! Consider that the average ABS car has more occupancy protection such as air bags, and ESP, EBD and so on, then this statistic is startling!]

Squirrel has hit on the problem with ESP and to use his words “you get little or no warning before the car breaks the performance envelope”. ESP is fantastic up to the limits, better than any driver, but when you go beyond ESP and slide you are well beyond driver skill and can only try and do the right things in the hope that conditions will change to within ESP’s abilities.

The transmission system is not a factor of ESP, it is tailored to an individual car.
In a “sophisticated AWD”, to which I presume is meant an Electronic Limited Slip Differential as a centre diff, then I have news for you. These cars drives as a front-wheel drive and the eLSD will not transmit torque to the rear axle at speed or cornering as this would effect handling. The eLSD is in fact a traction control system that reduces torque from spinning front wheels, but rather than brake intervention ‘robbing’ available torque, the torque is spread to the rear axle for improved acceleration. They also disengage under high demand such as off-road or snow and ice to prevent over heating and excessive wear.

However I note that a reference is made to Audi A4 and Torsen Diff which is quite different to eLSD. Torsen is considered superior but in practice only able to be fitted to longitudinal engined cars.

ABS v Cadence braking? It’s a no contest – ABS.
ESP v Driver control? Again no contest – ESP.

ESP intervenes to prevent a sideways slide. Torsen (Torque Sensing) Differentials distribute the torque between wheels/axles to find an optimum distribution for traction with no regards to sideways slippage.

And who believes that most drivers don’t activate ABS? Well just how do they know? ABS intervenes with brake pressure well before the familiar pulsing!! There is more to ABS than electronic cadence braking!

Graball: You raise a pertinent point – just how many people will be “saved” by ESP (and ABS)? It is my personal view that a lack of understanding of just what modern car driver aids can do has resulted in drivers raising their perceived acceptable levels too high in belief that technology is their saviour.

When you consider all the speed cameras, reductions in speed limits, traffic calming, road improvements, advances is car handling and occupancy safety, yet road deaths seem not to benefit, then surely something is wrong?

Reducing speed won’t help. People will just drive closer, brake later etc and nullify the safety gain because they think technology is their co-driver.

What is needed is better education. If you can’t drive a manual with an automatic, why can you drive an AWD after passing a test in front wheel drive?

Whilst I give the ABS and ESP the “no contest” thumbs up, I have no objection to non-electronic aided cars. Its just a matter of understand what’s what and driving accordingly although I have personal preference for non-aided cars as this give a rawer experience and enhances driver skill. The aids simply rob the driver of those skills over time as they are not used. If fact I have had ABS electronically disengaged (and yes it is legal as long as you tell your insurer as it is a modification). As well as the power steering dumbed down.

My proposal to get things rolling, is that before taking delivery of a new car, a purchase should pass a government test of understanding relevant to that car. I would expect people to demonstrate that they know that ABS may increase braking distances. ESP has its limits. AWD’s often do not drive the rear axle at speed and cornering. I am sure that the money spent on current ‘initiatives’ would easily fund and police such a scheme.

Ignorance is not bliss.

I would also like to see the driving test and obviuously lessons pre that, to include skid pan driving (proper skid pan not a cradle). The Finns have to go through this and there is no denying that their handling skills are some of the best and this is why they make such excellent motorsport drivers.

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My views do not represent Safespeed but those of a driver who has driven for 39 yrs, in all conditions, at all times of the day & night on every type of road and covered well over a million miles, so knows a bit about what makes for safety on the road,what is really dangerous and needs to be observed when driving and quite frankly, the speedo is way down on my list of things to observe to negotiate Britain's roads safely, but I don't expect some fool who sits behind a desk all day to appreciate that.

Ah those Flying Finns who's national sport is Rallying! But what you have to remeber is that alot of Finnish main roads are dirt tracks. So when the likes of Hannu Mikola and his countrymen, pop over here for the rally of Great Britian - to them its like popping down to the shops.
If we are seriously going to develop British rallying talent, we need to change rallying itself. ie add speed bumps, cameras, pedestrial refuges, traffic calming chicanes and min-roundabouts on every stage to level up the playing field.

Welcome along, Lucy.

Lol....keep it up Lucy. We need a few people on this site that can laugh at themselves....

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My views do not represent Safespeed but those of a driver who has driven for 39 yrs, in all conditions, at all times of the day & night on every type of road and covered well over a million miles, so knows a bit about what makes for safety on the road,what is really dangerous and needs to be observed when driving and quite frankly, the speedo is way down on my list of things to observe to negotiate Britain's roads safely, but I don't expect some fool who sits behind a desk all day to appreciate that.

sorry. i do.
based on anecdotal evidence from friends and family.

but i also work in the industry, i'm fairly sure i can dig up some studies and papers if you're that interested.

you'll have to be more specific with the phrases, they dont sit well with me but are a bit too vague to respond to:
"ABS intervenes with brake pressure well before the familiar pulsing!!"
(as soon as the ABS closes a valve to make any kind of intervention there's an effect on the pedal feel)
and
"There is more to ABS than electronic cadence braking!"
(yup its alot more intelligent than cadence braking)

Ed-M: My first experience with ABS was in a Honda Accord - E-reg, acquired after a long happy relationship with a non-ABS 1983 Accord.

It had what I consider to be a detrimental effect which I described as a dashpot effect. If one stamped on the pedal of a non-abs brake pedal (ie my '83 Accord) all effort went toward moving fluid toward the pads. In my E-reg Accord, there was a notable dashpot effect, presumably pushing back against the ABS pistons, which meant that for the first crucial few hundredths of a second, there was negligible retarding. I got into the habit of overcoming this by "taking up the slack" very early - lots of people momnitoring my brake lights must have thought I was a nervous driver when I did this in preparation for unforeseens that, for the most part, did not develop and did not require me to do more than ease off.

Any thoughts on that - and Lucy, is this the effect you were referring to?

Ed M:
Thanks for your offer of technical paper but in fact have quite enough – but saying that I never say never! So I was wondering what you might be kind enough to get you hands on?

To explain ABS: The first “stage” of ABS is to close the inlet valve preventing further pressure being applied to the brake and this is undetectable to the driver, because the driver will still feel the same pressure under the pedal, but he is now only pushing against the inlet valve rather then the brake calliper. Very often this intervention is sufficient and the inlet valve is reopened for normal braking to resume.

It is this undetectable intervention that, in my opinion, deprives the driver of realising that is braking too hard and therefore travelling too fast, luring him to drive closer to the limits.

However, if this “stage 1” is insufficient the familiar brake pedal pulse stage is activated, which more people are familiar with. In brief, with the aid of a pump to create pressure, inlet and outlet valves create an on/off cadence effect beyond and driver natural ability.

I have an ABS de-activated car and as a result, my wheels lock up “sooner” because there is no stage 1 ABS. However that conditions me to drive slower, whereas with stage 1 of ABS I would be oblivious that I peaking on the edge of traction. Perhaps this is part of the shocking ABS fatality statistic?

The proof is in the eating so to speak. When I first disengaged the ABS, I kept locking up as my driving style had been conditioned to harsher braking. You can try this for yourself by pulling the ABS connector from under the bonnet (your dash board will go hay-wire) and you will find that your car will lock-up before you expect it – because you simply didn’t know that stage 1 of ABS was operating before and have been conditioned to harsher braking – its not bad driving, since such style is appropriate to driving an ABS. My point is people are unaware that ABS is functioning this way and they are closer to the limits than they realise.

Roger:
Having read my thread again and now regretting it was so long, I am not sure which effect of mine you are referring to. However to your scenario.

My experience is such faults or characteristics are dismissed as rubbish or impossible – ABS can’t fail etc etc. Whilst ABS is an extremely reliable electronic device – it has mechanical parts!

However, if fault finding drew a blank, I would check to see if there was some “slack” or give in the upper regions of brake pedal arm. Perhaps you are initially taking up some slack this way?

Then do the brakes need bleeding? Well you don’t know, so I would change the fluid and bleed them. Also the servo may be an issue, but I don’t have a clue about them so I can’t say anymore on that.

Of course it is quite feasible that an ABS valve is “sticking”, reducing pressure to the brakes, until a pressure is reached that “shunts” it out of the way. And I feel that your early brake feathering could well have been a cure to push the valve back with the fluid to make the brake line free from this obstacle for when braking in earnest was required. And at E-reg my bet is such a fault might not be traced by electronic fault finding.

Having considered the mechanics and fail safe positioning of the solenoid valve I can only foresee two ways this could happen;
1 The return spring has failed so the valve is drifting in and out of the brake line obstructing the flow.
Or 2 a faint short that is partially closing the valve but not enough to resist pedal pressure.
Of course 1 & 2 are extremely unlikely but not impossible.

If the fault was cleared for a while after feathering the break, then,1, a “loose” valve sounds the better bet. If the fault immediately returned then I would speculate that was (2), a permanent faint short.

However if the truth is known, its probably none of these suggestions!

I can confirm the official policy of one manufacturer/group in this scenario when under guarantee. It would be all the obvious mechanical checks. If there was nothing obvious, the ABS unit would be replaced as a precaution regardless of the absence of fault finding and even if the fault was intermittent and not detectable at the time of inspection.

So whilst the industry will pronounce ABS failsafe in public, in private they don’t take any chances! Probably because one scare story could send the public into a panic.

However I would stress that ABS faults and failures are extremely rare and would not want anyone to be alarmed by the possibilities I have speculated upon.

I have a mechanic friend who tells me that ABS does fail quite a lot and can cost £800ish to put right but what exactly fails and what symptoms it gives, I couldn't tell you. I wasn't too interested because my cars no longer have it and I'm happy to be without it.

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My views do not represent Safespeed but those of a driver who has driven for 39 yrs, in all conditions, at all times of the day & night on every type of road and covered well over a million miles, so knows a bit about what makes for safety on the road,what is really dangerous and needs to be observed when driving and quite frankly, the speedo is way down on my list of things to observe to negotiate Britain's roads safely, but I don't expect some fool who sits behind a desk all day to appreciate that.

I was referring to ABS intervenes with brake pressure well before the familiar pulsing.
Yes - it was a characteristic. I tried a couple of other Accords of that era, all of which exhibited the effect. I even corresponded (to no avail) with Honda UK on the topic. I am glad that undesireable effect has been designed out of the later ones.

It's lost in the mist of time now, but I'm fairly sure the dashpot effect was ABS, and that there was initial play designed in to the system.

I not only had the fluid replaced and bled through, but also had new discs in casse a minute warp on one or other was effectively pushing pads apart and creating additional play.

I don't think so. Gentle pressure on the pedal actually allowed it to travel quicker to the pad biting point than stamping on it. Significant pedal travel resistance prior to retardation was only felt when you "took a run" at the pedal.

Agreed re fault finding - that was designed to check it did its job, not to see if it buggered up the normal braking aspect. This was a design fault. If you're interested, and I can find them on an old PC, I'll dig out my letters and PM them to you (or post on here if anyone else is interested).


You miss:
3. Design fault. That is what I think it had.

I never tested that explicitly, but I suspect the latter (I think I'd have noticed if the problem went away after one "stamp" for a while.


I agree.

I notice you've got ABS disconnected in one of your cars. I do hope you've also disconnected, or at very least restricted the back brakes too? Non-ABS-equipped cars have a compensator to prevetnt rear lock-up when the weight transfers to tyhe front. Most (though not all) cars with ABS saved that as an unnecessary feasture as ABS trumps it (which it does, unless turned off or disconnected!).

I don't find any need for esp on my small light square cars. however on a long weighty or powerfull car and vans and people movers I recon it is worth concidering. I had a near roll in my works van. The only trouble is that the esp might have let me carry on into the hard object I was trying to avoid..... A house. I would rather have rolled the van in thier garden than hit a house. It takes another option away.

Before I get roasted for this incident it was a horrible corner with a poor road surface in a horrible talbot commer van with the front track much narrower than the rear. This gave the beast horrible responses when breaking on a corner. I simply could not scrub off enough speed prior to the corner. There was deffinatly a degree of driver error too.

If the van had been squarer or had ABS or the road surfice grippier it would not have happened.

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Speed limit sign radio interview. TV Snap Unhappy
“It has never been the rule in this country – I hope it never will be - that suspected criminal offences must automatically be the subject of prosecution” He added that there should be a prosecution: “wherever it appears that the offence or the circumstances of its commission is or are of such a character that a prosecution in respect thereof is required in the public interest”
This approach has been endorsed by Attorney General ever since 1951. CPS Code

The ESP would not have taken the option you chose away from you, but might have provided an alternative from the two invidious choices you've identified here.

Roger, I think the salient points of the correspondence would be interesting for everyone. I image people read without posting sometimes, so in fact there may be more people interested.

However can I anticipate that your letters refer to a design fault and Honda refers to a "characteristic"? lol

My ABS was disengaged electronically by the manufacturer altering the parameters/coding. Bizarrely this is neither illegal nor a MOT failure since the ABS Warning lamp functions as normal. I notified my insurers as well and they didn’t bat an eye lid!

All cars have a permanent brake force proportioning valve for front to rear, in case the ABS Unit (EBD function) fails. My car did not have EBD or one of those mechanical valves between the rear axle and body that operate as the body rises from the axle under hard braking for “fine tuning” of brake bias.

Anton: Those Commer vans? Does anyone know why they made them narrower tracked at the front? It seems to defy common sense?

that's fair enough lucy, i dont have any more evidence for this than your anecdotal experience.

personally i'd be surprised if the threshold between isolating, and dumping/building pressure is great enough to have a great effect.

my anecdotal evidence is things like my mother in law telling me how much better the braking is on her new car because it has ABS.

That effect I believe is detrimental - vital hundredths of a second lost when the vehicle is still travelling at the un-braked speed, which I suggest on dry roads with good fat tyres cannot be made up by ABS =- and may make a serious difference in collission speed.

By cruel fate, the correspondence with Hondas UK JUST preceded my PC days. I would have passed my faded carbons and replies on to the purchaser of the vehicle, sorry.

hi roger,

i didnt respond to your post as i didn't really want to start speculating on what kind of system was in play on the honda 20years ago.

there's no reason (i can think of off the top of my head) on a modern ABS system why all initial brake pressure from the master cylinder shouldnt go straight to the wheels (apart from a stuck valve).