RAY, Your quote:
"Tests have proved that stopping distances for solo cars are increased when ABS is fitted.
Not reduced.
Tests have proved that stopping distances for solo cars are increased when ABS is fitted.
Not reduced.
However ABS will allow you to steer round a hazard under heavy braking."
Please state the source of this incorrect information. Judging by the last statement regarding steering around a hazard, I think someone has confused ABS with ESP.
"Tests have proved that stopping distances for solo cars are increased when ABS is fitted.
Not reduced.
Tests have proved that stopping distances for solo cars are increased when ABS is fitted.
Not reduced.
However ABS will allow you to steer round a hazard under heavy braking."
Please state the source of this incorrect information. Judging by the last statement regarding steering around a hazard, I think someone has confused ABS with ESP.
Just to lighten things ...
If someone has got ESP then they would be extremely safe, as they would know of the hazards before they saw them!
If someone has got ESP then they would be extremely safe, as they would know of the hazards before they saw them!
I take it that was meant as a joke.
Of course, I was not referring to extrasensory perception but to Electronic Stability Programmes (or what Land Rover and some other manufacturers call DSC, Dynamic Stability Control)
Of course, I was not referring to extrasensory perception but to Electronic Stability Programmes (or what Land Rover and some other manufacturers call DSC, Dynamic Stability Control)
We've had this discussion before and I think it went along the same lines then.I'll repeat my post from earlier...
Just to comfirm what Lutz is saying .Some years ago one the the caravan mags tested stopping distances of cars with ABS and cars without, both towing and solo. The shortest stopping distance was achieved by the car with ABS towing a caravan.
Can't remember the explaination why this happens but I do know the test was done and the results were , as Lutz rightly says,
A car with ABS towing a caravan will stop quicker than a car with ABS solo.
Brian
Just to comfirm what Lutz is saying .Some years ago one the the caravan mags tested stopping distances of cars with ABS and cars without, both towing and solo. The shortest stopping distance was achieved by the car with ABS towing a caravan.
Can't remember the explaination why this happens but I do know the test was done and the results were , as Lutz rightly says,
A car with ABS towing a caravan will stop quicker than a car with ABS solo.
Brian
Re annual inspection of caravans.
A better idea would be to have the annual MOT or test (as commercial articulated trailers require)carried out by VOSA. These examiners are experts and there are many testing stations around the country where these tests could be carried out. This would avoid the dodgy dealers doing the test. Another answer would be for dealers to be authorised as testers by VOSA, similar to present MOT testing stations.
A better idea would be to have the annual MOT or test (as commercial articulated trailers require)carried out by VOSA. These examiners are experts and there are many testing stations around the country where these tests could be carried out. This would avoid the dodgy dealers doing the test. Another answer would be for dealers to be authorised as testers by VOSA, similar to present MOT testing stations.
Very good idea Ewan, it would also make the caravan servicing agents pull there socks up and get the job done right, knowing full well that if they carry out any remedial work, if not done up to standard will be refused a certificate of road worthiness by VOSA.
Allan.
Allan.
Unless I'm mistaken, it was a technical article in the Caravan Club magazine about a year ago.
Still no hard facts Lutz!
Taken from the caravan club handbook: To carry out normal road maneuvers with increased care to take in to account the length of the outfit, the vehicles reduced acceleration, and its longer stopping distances when braking. I think that is sound advice don't you Lutz? And will certainly not give any new comer reading these posts a Dangerous false sense of security.
Allan.
Still no hard facts Lutz!
Taken from the caravan club handbook: To carry out normal road maneuvers with increased care to take in to account the length of the outfit, the vehicles reduced acceleration, and its longer stopping distances when braking. I think that is sound advice don't you Lutz? And will certainly not give any new comer reading these posts a Dangerous false sense of security.
Allan.
As I said, I'm not at home at present so I don't have access to the article but Brian (St. Albans) has confirmed the result.
As a non-techie it makes perfect sense to me. Brake heavily solo, and there is a significant weight shift to the front axle. Brake heavily with a caravan, and there is 75kg noseweight plus the increased dynamic weight on the ball caused by the caravan wanting to push into the car. I can see that this will increase the rear axle load and allow the rear brakes to be more effective.
I remember what caused the previous debate - someone said that they had been scared by "under heavy braking the caravan pushing the car forward into a roundabout". Lutz and co explained that this was not possible with correctly functioning caravan brakes.
I remember what caused the previous debate - someone said that they had been scared by "under heavy braking the caravan pushing the car forward into a roundabout". Lutz and co explained that this was not possible with correctly functioning caravan brakes.
I can also recall the article refered to by Lutz and Brian. Just trying to remember which magazine ran the article but it must have been 2/3 year ago. I can also recall the thread on this forum which debated it, one contributor recalled having to carry out an emergency stop with the caravan in tow and said that experience endorsed the facts in the article that stopping distance was improved.
i,d just like to say what lutz is saying is correct.earlier on in this thread it was said" A loaded hgv will stop better/earlier than an unladen hgv"The answer is yes .the brake effeciancy increases by over 50% when loaded .why? nothing to do with ground pressure but because of a load sensing valve.the same applies to cars ,push down on the back LSV opens more ,but front of car does,nt rise up because its not pivoting halfway down its wheelbase.now at which point of braking is the brake most effective?
Simon - you should be pleased that your insurance company told you of their concern. Far better to know before than have a claim denied after an accident!
Whilst the 85% is a "rule of thumb" - anyone who exceeds it is being very stupid unless they have it in writing from their insurance company that they (the insurance company) have considered what is being done and are still prepared to offer cover.
If you can get such a written confirmation - great!
But for those that exceed this "rule of thumb" - beware! you could find yourself uninsured in the event of an accident.
Whilst the 85% is a "rule of thumb" - anyone who exceeds it is being very stupid unless they have it in writing from their insurance company that they (the insurance company) have considered what is being done and are still prepared to offer cover.
If you can get such a written confirmation - great!
But for those that exceed this "rule of thumb" - beware! you could find yourself uninsured in the event of an accident.
Lutz
this goes some way towards explaining the point re abs brakes i was trying to get across.
see this link
http://www.telegraph.co.uk/motoring/main.jhtml?xml=/motoring/2002/08/02/emrip03.xml
Take a brake
From my physics course I seem to remember that maximum braking efficiency occurs just before the wheel stops rotating and then begins to skid or slide. I don't think a non-ABS car would stop sooner on a dry surface with the wheels locked and almost certainly an ABS car will stop better on contaminated surfaces unless the driver is very skilful.
J.A.P., Esher
Drivers are not skilful enough, they just believe they are. In the UK alone, more than 90 per cent of all accidents are caused by human error and it's a sad fact that current basic training standards aren't up to the job of ensuring safety on the road. You are correct in your understanding about when braking is at its most efficient - just prior to the wheels locking. Manually braking like this in an emergency, however, is one of the hardest things to learn. It is known as threshold braking, whereby a driver generates the maximum braking force just prior to wheel lock-up. The sensitivity and cool head required for this are expert-only qualities.
Most drivers faced with an emergency will simply stand on the brake pedal, which does two things in a non-ABS car. First it removes all steering control and second, on anything other than a dry, smooth surface, or freshly fallen snow, it increases the braking distance. By repeatedly stamping on the brake pedal (cadence braking), drivers can mimic the effect of ABS and retain steering control, but again this is a technique that requires expert tuition and much practice and it is never as efficient as ABS.
Best by far is a modern ABS system with electronic brake force distribution, which uses wheel sensors and a computer to measure how near to lock-up each wheel is. It then modulates the brake line hydraulic pressure around the point of lock-up, maintaining almost maximum stopping power to each wheel while retaining steering control. In a critical emergency, braking distance is often academic; it is the ability to steer round a hazard that can save the day, yet few drivers understand this or how to use their ABS brakes to enhance safety.
this goes some way towards explaining the point re abs brakes i was trying to get across.
see this link
http://www.telegraph.co.uk/motoring/main.jhtml?xml=/motoring/2002/08/02/emrip03.xml
Take a brake
From my physics course I seem to remember that maximum braking efficiency occurs just before the wheel stops rotating and then begins to skid or slide. I don't think a non-ABS car would stop sooner on a dry surface with the wheels locked and almost certainly an ABS car will stop better on contaminated surfaces unless the driver is very skilful.
J.A.P., Esher
Drivers are not skilful enough, they just believe they are. In the UK alone, more than 90 per cent of all accidents are caused by human error and it's a sad fact that current basic training standards aren't up to the job of ensuring safety on the road. You are correct in your understanding about when braking is at its most efficient - just prior to the wheels locking. Manually braking like this in an emergency, however, is one of the hardest things to learn. It is known as threshold braking, whereby a driver generates the maximum braking force just prior to wheel lock-up. The sensitivity and cool head required for this are expert-only qualities.
Most drivers faced with an emergency will simply stand on the brake pedal, which does two things in a non-ABS car. First it removes all steering control and second, on anything other than a dry, smooth surface, or freshly fallen snow, it increases the braking distance. By repeatedly stamping on the brake pedal (cadence braking), drivers can mimic the effect of ABS and retain steering control, but again this is a technique that requires expert tuition and much practice and it is never as efficient as ABS.
Best by far is a modern ABS system with electronic brake force distribution, which uses wheel sensors and a computer to measure how near to lock-up each wheel is. It then modulates the brake line hydraulic pressure around the point of lock-up, maintaining almost maximum stopping power to each wheel while retaining steering control. In a critical emergency, braking distance is often academic; it is the ability to steer round a hazard that can save the day, yet few drivers understand this or how to use their ABS brakes to enhance safety.
,d just like to say what lutz is saying is correct.earlier on in this thread it was said" A loaded hgv will stop better/earlier than an unladen hgv"The answer is yes .the brake effeciancy increases by over 50% when loaded .why? nothing to do with ground pressure but because of a load sensing valve.the same applies to cars ,push down on the back LSV opens more ,but front of car does,nt rise up because its not pivoting halfway down its wheelbase.now at which point of braking is the brake most effective?
Where in the thread does it state this? Are you talking from experience? I have yet to come across any HGV vehicle where you can treble its weight and it makes its brakes 50% more efficient! Just get back to basics, remember this man Sir Isaac Newton? And I will reiterate what I have already stated, please do not give miss leading information that could be dangerously misinterpreted by a novice, or even an experienced caravaner, don't forget when we start talking about brakes we are talking about a very important subject, so for safety's sake lets not play games with he said, Ray said, Lutz said, and air on the side of caution, and always presume that when you increase your payload be it towed or otherwise you will increase your stopping distance. One little foot note when the police convert there cars, because of all the extra weight carried, they have the brakes up rated, and that's a fact. Speaks volumes.
Where in the thread does it state this? Are you talking from experience? I have yet to come across any HGV vehicle where you can treble its weight and it makes its brakes 50% more efficient! Just get back to basics, remember this man Sir Isaac Newton? And I will reiterate what I have already stated, please do not give miss leading information that could be dangerously misinterpreted by a novice, or even an experienced caravaner, don't forget when we start talking about brakes we are talking about a very important subject, so for safety's sake lets not play games with he said, Ray said, Lutz said, and air on the side of caution, and always presume that when you increase your payload be it towed or otherwise you will increase your stopping distance. One little foot note when the police convert there cars, because of all the extra weight carried, they have the brakes up rated, and that's a fact. Speaks volumes.
I'd agree with Allan here. I never said that a fully laden HGV would be able to stop quicker than an unladen one. I said a fully laden car towing a caravan would be able to stop quicker than a fully laden car solo, so long as the caravan is capable of stopping itself (which, if its brakes are correctly maintained and adjusted will be the case).
hello allan, as a matter of fact i am talking from experiance,20 years of it and it is FACT.get your self to a "vosa" test station and watch a brake test on a hgv.why do you think proportional valves where introduced?to clean the windows?no to stop A lorries jacknifing and B cars going into skids.please dont you mislead people.
Hello G,
If an insurance company tried to limit its liability for claim on the basis that an outfit was loaded above 85%, then they would be on a very sticky wicket legally, provided the vehicle is rated above 85%.
The only way they could apply that type of restriction and make it stick would be to make a very clear clause in the policy offer statement before the policy is issued (as has happened for Simon at the start of this thread).
Watch out for renewal documentation where they might sneak in something to that effect.
Whilst the lower the ratio generally the better, 85% is not a magical figure that automatically makes an out fit unsafe if it is exceeded. As with any driving activity the driver must be aware of the risks and make allowances for the performance and handling of what ever they drive
If an insurance company tried to limit its liability for claim on the basis that an outfit was loaded above 85%, then they would be on a very sticky wicket legally, provided the vehicle is rated above 85%.
The only way they could apply that type of restriction and make it stick would be to make a very clear clause in the policy offer statement before the policy is issued (as has happened for Simon at the start of this thread).
Watch out for renewal documentation where they might sneak in something to that effect.
Whilst the lower the ratio generally the better, 85% is not a magical figure that automatically makes an out fit unsafe if it is exceeded. As with any driving activity the driver must be aware of the risks and make allowances for the performance and handling of what ever they drive
Seth there is no need to be rude, okay agreed, empty HGV load it and its brakes are more efficient by 50% but what is the load margin over the unladen vehicle? 50%? No, well over 200% running at 44 tons so what happens to the other 150% of momentum that you have just added? That's right it keeps on rolling way past where the 14ton vehicle would have come to a halt, pure physics, no tricks no magic, screw as many LCV as you like in, but you will not stop 44 tons over 14 tons quicker. Way before your 20yrs exp ( at what I do not know as you never mentioned it, and no I am not being pedantic) Hope used to fit a device to lorries(The Hope anti jack knife device) to help reduce the possibility of a jackknife occurring, notice I say help, not to as you say to stop them, as to date there is no way of completely alleviating the problem of any vehicle from whipping round and greeting it's self, And likewise to your comment "B"to stop cars going into skids.( Common daily acurance) So there you are, you have given quite a lot of misleading information, no doubt like Lutz purely unintentionally, and with the best intensions, but never the less, lets all remember that we are talking about safety related issues here, not awnings or what is the best camping chair, and unless anyone has the appropriate qualifications to advice otherwise then please lets all air on the side of safety and respect the fact that a grater given mass is far more difficult to stop in momentum than a lesser one, and we have never mentioned the amount of energy involved in stopping that mass, and we all know what energy produces "heat" put that in the pot and you will reduce your braking effect even further, but we don't want to go down that road.
Allan.
Allan.
Hello Allan,
I too agree with Lutz's principal on this point,
All vehicles should have their braking system designed to cope with the maximum load it will carry. This applies to cars and lorries. We must not forget that the tyres are also a very important part of the braking system so some consideration must be given to these as well.
But let us first consider the size of brake mechanisms. In essence if a vehicle is designed to have an all up mass of 1T then brakes of an appropriate surface area will be fitted. If the vehicle is designed for 2T then the brakes will require twice the surface area to achieve the same rate of retardation. The same principal applies all the way up to 44Tonners. Thus in theory it should be possible for a 44T to stop in the same distance as a 1T car.
Given that a 44T probably has an unloaded mass of only 11T (approx 25%) for much of its life the brakes are larger than necessary. Equally the tyres will be inflated to cope with 44T but at lower loading the tyres are technically over inflated. This is important as it reduces the tyres contact area with the road, and that will affect braking performance.
So a partially loaded vehicle will have over sensitive brakes and a reduced road contact area that will prevent maximum braking efficiency from being achieved, the result is evident in longer stopping distances, and witnessed by the number of skid marks made by unladen trailers when approaching junctions.
The same applies to cars, but the ratio of unloaded to loaded configurations is less dramatic, also most car manufactures recommend resetting tyre pressures depending on load and speed.
I too agree with Lutz's principal on this point,
All vehicles should have their braking system designed to cope with the maximum load it will carry. This applies to cars and lorries. We must not forget that the tyres are also a very important part of the braking system so some consideration must be given to these as well.
But let us first consider the size of brake mechanisms. In essence if a vehicle is designed to have an all up mass of 1T then brakes of an appropriate surface area will be fitted. If the vehicle is designed for 2T then the brakes will require twice the surface area to achieve the same rate of retardation. The same principal applies all the way up to 44Tonners. Thus in theory it should be possible for a 44T to stop in the same distance as a 1T car.
Given that a 44T probably has an unloaded mass of only 11T (approx 25%) for much of its life the brakes are larger than necessary. Equally the tyres will be inflated to cope with 44T but at lower loading the tyres are technically over inflated. This is important as it reduces the tyres contact area with the road, and that will affect braking performance.
So a partially loaded vehicle will have over sensitive brakes and a reduced road contact area that will prevent maximum braking efficiency from being achieved, the result is evident in longer stopping distances, and witnessed by the number of skid marks made by unladen trailers when approaching junctions.
The same applies to cars, but the ratio of unloaded to loaded configurations is less dramatic, also most car manufactures recommend resetting tyre pressures depending on load and speed.
Excellent valid points, but do not forget the LCV & ABS, also play there part in bringing an unladen vehicle to a halt, long gone are the days when you could lock up a trailers wheels at every other road junction. I take on board the points that you have made and in theory very good ones, and as I said earlier " I have no technical knowledge to back this up, just pure through the seat exp of over more than 35yrs driving with all types of trailers to base my findings on"
"All vehicles should have their braking system designed to cope with the maximum load it will carry. This applies to cars and lorries". Yes my car no doubt was, so was my caravan, but in the case of my car it has 4 x 302mm disc brakes fitted with abs and all the other bells and whistles to help it stop, caravan of a similar weight as I tow @ around 92% has in comparison two very small drum brakes that are very old in design and operating principle, so how can that enhance my overall stopping distance? As I have already stated from experience my car loaded or unloaded will stop in a shorter distance than when it is towing a trailer, as you have already stated "All vehicles should have their braking system designed to cope with the maximum load it will carry" so the trailers brakes are there to assist in bringing it to a halt not to improve the overall stopping distance. And as I have said before in makes dame good sense to air on the side of caution and allow a greater stopping distance, surely this is why all the motoring organizations / cc and the ccc endorse this, and surely they cant be wrong as they have what we do not Technical knowledge.
Allan.
"All vehicles should have their braking system designed to cope with the maximum load it will carry. This applies to cars and lorries". Yes my car no doubt was, so was my caravan, but in the case of my car it has 4 x 302mm disc brakes fitted with abs and all the other bells and whistles to help it stop, caravan of a similar weight as I tow @ around 92% has in comparison two very small drum brakes that are very old in design and operating principle, so how can that enhance my overall stopping distance? As I have already stated from experience my car loaded or unloaded will stop in a shorter distance than when it is towing a trailer, as you have already stated "All vehicles should have their braking system designed to cope with the maximum load it will carry" so the trailers brakes are there to assist in bringing it to a halt not to improve the overall stopping distance. And as I have said before in makes dame good sense to air on the side of caution and allow a greater stopping distance, surely this is why all the motoring organizations / cc and the ccc endorse this, and surely they cant be wrong as they have what we do not Technical knowledge.
Allan.
The reason why caravans have smaller brakes than one may expect when comparing with those of cars is that caravan chassis are only designed for 60mph whereas cars are capable of often twice that. In addition, as I have said elsewhere, few drivers have sporting ambitions when towing a caravan and this, too, is taken into account in dimensioning the brakes. Under conditions of normal duty, the brakes on the caravan provide adequate braking performance.
Just to add another note. Because caravan brakes are not equipped with ABS (yet), you will find that their performance is normally good enough to lock the wheels even on a dry road surface during an emergency brake and you can't expect more than that.
Agreed, it does what it says on the tin, no more no less, and will certainly not improve the overall stopping distance over a solo car, or as you say Lutz "adequate braking performance" and correctly adjusted trailer brakes should never lock up under any braking conditions, once you do that you have in effect lost control, and have reduced the braking efficiency of that combination.
Allan.
(starting to go round in circles)
Allan.
(starting to go round in circles)
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