Anyone know if any tests have been done to find out how stopping distances are affected when towing a van in the dry and wet? How much distance should an outfit have from the car infront at 60mph, solo you shoud be able to count 2 secs by using a fixed marker
Serious one - Stopping distances
- Thread starter CaptainKangaroo
- Start date
One of the mags did some tests a few years back.They tested solo with ABS.solo without,towing with ABS and towing without.The shortest stopping distance overall was achieved by the towing with ABS setup.
Physics dictates that stopping distances will increase in the wet for all types of solo or outfits because the friction between the tyre and the road surface will be lubricated by the water. Its also a fact that the greater the moving mass, the more energy the system has, and so it will require more energy to be dissipated to bring the outfit to a halt. The stopping distance is dependant on the effectiveness of the brakes, but it is likely that a car and caravan will require a greater distance to stop than just the solo car.
The above will definitely be true for unbraked trailers where the the car has to provide all the braking effect.
The above will definitely be true for unbraked trailers where the the car has to provide all the braking effect.
but that doesn't make sense due to the total mass of the outfit. I would expect distances to be greater not shorter, can you explain?
I've been looking to see if I can find these results , but no joy yet. I think possibly the distance was shorter due to the additional braking force of the caravan on the back, a bit like a parachute on a drag car perhaps?
Although it sounds strange that a car/caravan outfit can stop quicker than the same car solo, it can be relatively easily explained. When the brakes on the caravan act, the caravan will try to pitch forward, applying more noseload to the towball. The resulting downward force on the towbar will, in turn, increase the rear axle load on the car, providing more available braking performance at its rear wheels. However, this effect only holds true for cars fitted with ABS because they have a variable distribution of braking forces between front and rear wheels. Without ABS, the front wheels are doing most of the braking and an increase in rear axle load is not going to help.
Of course, the whole thing only works if the caravan has very good brakes, too. Nevertheless, even under less than ideal conditions, the braking distance when towing (with ABS) is not likely to exceed the solo result by more than 10% (all other conditions being equal). That braking is worse in the wet, stands to reason, and that applies regardless whether solo or towing.
Of course, the whole thing only works if the caravan has very good brakes, too. Nevertheless, even under less than ideal conditions, the braking distance when towing (with ABS) is not likely to exceed the solo result by more than 10% (all other conditions being equal). That braking is worse in the wet, stands to reason, and that applies regardless whether solo or towing.
Lutz, I'm not convinced by your posting, surely as John L stated the greater mass will require more force to ****** the speed.
I think this would be a good feature in the mag, although the one on sink drainage was riveting.
What say you PC mag?
I think this would be a good feature in the mag, although the one on sink drainage was riveting.
What say you PC mag?
A greater mass will take longer to stop but only if using the same force to stop it ,ie the tow car brakes. But surely in this case the stopping force is also being increased with the caravan brakes, more so with a twin axle ,and if the tow car rear wheels also get more grip all of these factors together with the abs probably explain the shorter stopping distance . Maybe someone else can remember reading the article I mentioned, I distinctly remember the results as the author, for obvious reasons ,made a big thing of it.
This is a no win topic, because there are so many variables to take into account.
I acknowledge Lutz's and Brians technical description of how an outfit can potentially out brake a solo car and I have experienced the grabbing effect of a traler brake acting.
For safety I personally will always assume it will take a greater distance to stop a car and caravan compared to a solo car and make provison in my driving. especially on an downward slope where brake fade can beceome an issue.
I acknowledge Lutz's and Brians technical description of how an outfit can potentially out brake a solo car and I have experienced the grabbing effect of a traler brake acting.
For safety I personally will always assume it will take a greater distance to stop a car and caravan compared to a solo car and make provison in my driving. especially on an downward slope where brake fade can beceome an issue.
John ,I think your assumption is right.Results on a test track,with perfect conditions and using perfect equipment bare no resembulance to the reality of day to day driving.
Key to the whole story is that to get good braking performance, you need to make sure that all the braking effort is actually getting through to the road surface and the tyres aren't skidding due to inadequate wheel load. When car and caravan is braking, there is undoubtedly a load transfer on the car's rear axle and the ABS puts this to good use.
That's also why the speed limit in Germany for cars towing caravans is 80kph without ABS and 100kph with ABS.
That's also why the speed limit in Germany for cars towing caravans is 80kph without ABS and 100kph with ABS.
Lutz, the law in germany is very interesting, they have obviously taken the time to test outfits. Are people in this country who tow with a non abs car aware that the stopping distances are different than those with abs?
I think that the govt ought to test and advise
I think that the govt ought to test and advise
The braking distance is shorter with ABS regardless of whether you're towing or solo but the difference is even more noticeable when towing and/or in the wet.
One can't give a hard and fast rule how much ABS improves the stopping distance because it depends so much on the conditions. ABS is meant to be a sort of insurance policy against the unexpected not any justification for taking advantage of the improvement it gives.
I have had the experience of an emergency stop in a car with ABS and a 1500kg van on the back. what I will say it you will not expect what happens.
firts the car feels like it is not braking at all, so you force the brake and the ABS starts, then you hit a brick wall as the caravan loads the rear and applies its brakes. we went from about 40 mph to zero in a VERY short distance. both my brother and I had seat belt marks from the force.
Then instantly you panic that nothing is behind you as you realise the stopping distance you used was too short for anyone a bit close.
This was on a warm dry day, and was caused when a child ran out of a concealed driveway straight into the main road. the parents have now cut down the hedge to make sure people can see into the drive. they also made us a nice cuppa while I checked the van and car for any damage.
firts the car feels like it is not braking at all, so you force the brake and the ABS starts, then you hit a brick wall as the caravan loads the rear and applies its brakes. we went from about 40 mph to zero in a VERY short distance. both my brother and I had seat belt marks from the force.
Then instantly you panic that nothing is behind you as you realise the stopping distance you used was too short for anyone a bit close.
This was on a warm dry day, and was caused when a child ran out of a concealed driveway straight into the main road. the parents have now cut down the hedge to make sure people can see into the drive. they also made us a nice cuppa while I checked the van and car for any damage.
TRENDING THREADS
-
-
-
-
Awning rail on the house to help with drying air awning at home- Started by Steve1962
- Replies: 5
-
-
-
Facebook
Twitter