Stability - do other factors beside loading and weight matter?

[BaronsHuman]

I've towed a variety of caravans with various cars over the years and mostly without any concerns about the outfit becoming unstable. Predominantly this has been with estates but for the last two years with a freelander TD4, during which I have had a couple of incidents when I felt that the outfit was becoming unstable and the tail was wagging the dog.

The two obvious differences between estates and 4x4's are wheelbase length and centre of gravity height. Would these be significant or have the two incidents been down to other factors? Loading and outfit match being considered a constant, outfits have varied from 75% to the current 87% and I always load in a similar fashion and check nose weight.

Any thoughts would be apreciated

David

 

[colin-yorkshire1]

hi David, many things can cause instability from tyre pressures to wind direction given that the loading, servicing, ect is the same, one has to look at outside forces that put the van out of line while under tow, center of gravity could be a factor as could the vehicle foot print,
and funnily enough the tow ratio, most of the vans I have towed have been in the 85 to 100% range yet I have not had any issues while towing however my present outfit is 71% and it does not tow as well as some of the others, the only difference I can see apart from the weight ratio, is the car has a narrower gate and it is taller than the saloons I usually tow with, everything else is the same, however even considering all the variables I have come to the conclusion that the main difference is noseweight it had to come down from 75kg to 50kg and therefore the weight transfer from central to rear, must be a significant factor.

 

[Lutz]

Leaving weight and weight distribution aside, lateral suspension compliance, especially that of the towing vehicle's rear suspension, has a big influence on stability. This includes the lateral stiffness of the tyres, hence tyre aspect ratio and, obviously, tyre pressure. The stiffer the suspension and tyres, the better. Coupled with this is the rear overhang, i.e. the dimension from rear axle to towball. The larger this is, the less stabe the outfit is likely to be.

 

[colin-yorkshire1]

Hi Lutz, nice to hear from you, there is merit in what you say, the best tow car I ever used was a 1.7 Austin Maxi, it had progressive rear suspension "hydrolasic" and litrally a wheel at each corner, sitting quite wide on the road, the distance between the rear wheel and the towball being about 12in "30cm" considering in those days very few used a stabiliser, or bothered about tow ratios, (guess it was about 80%) or noseweight measurements, caravan stability was not an issue one came across.
given all the variables involved it is impossible to put a finger on what causes it and there are so many factors that can alter it I dont think there is a diffinative answer as all cases will be different.

 

[ProfJohnL]

Colin's revelations about his various outfits weight ratio's and handling characteristics amply demonstrates the main reason why I dislike the constant references to achieving an 85% ratio without consideration to other towing factors.

Good towing is not just down to a notional weight ratio, but its down to all the mechanical considerations Lutz mentions, the way a trailer is loaded to produce a noseweight, road and weather conditions, and of course the drivers driving style and the drivers expectations.

There is no certainty that every vehicle that can tow will actually tow well. Equally give the same car and caravan to two different drivers to load and tow, and one may find it fine whilst the other may have trouble with it.

 

[BaronsHuman]

Thanks for the replies, I guess the number of variables rules out any simple answer.

My question was prompted by some early thinking about my next tow car, I'm torn between sticking with a 4x4 maybe a Sorento or an estate likely contenders being an Audi A6 or Volvo

David

 

[colin-yorkshire1]

hi David,
dont be put off by one experience, yes maybe the COG of a 4x4 is higher but there are so many other factors that can influence the caracter of a tow vehicle, while I am not a 4x4 fan there is no doubt they make fine towcars thats why so many use them.

 

[NigelHutson]

Over the years, the Tow Car Awards event always throws up surprises. There are some superb tow cars out there, and equally there are also some dire ones. When we do the testing, it's under ideal circumstances (weather aside!) in that the cars and caravans are ballasted to give a decent weight together with a maximum noseweight, and it's done on test tracks. Generally speaking the scientific data retrieved from the performance testing backs up the other judges' "seat of the pants" feelings.
There are certain large 4X4's that are absolutely brilliant, but others that at times verge on being dangerous. As a previous post suggests, suspension set up, tyres, and rear overhang play a large part. For example, the previous Kia Sorento (2009-2013?) which we tested (without self-levelling suspension) was in my personal opinion (and I stress that it is my opinion, and not necessarily that of PC) one of the worst vehicles that we'd had. Many owners of the same vehicle have reported instability when SLS is not fitted. Owners with vehicles with SLS seem to be a much happier bunch.
With regards to saloon cars, the Jaguar XF was a huge surprise last year as it was truly excellent. The same applies to the BMW 520 which was a previous class winner. Yes, they're both expensive vehicles, and probably have more sophisticated suspension and lower profile tyres. Most of the winners (both class and overall) over the years have been of European manufacture. Could it be that they understand the towing requirements better than others?
I know that there are cynics out there who believe that the event is sponsored by certain Companies. The ONLY Companies to do the sponsoring are Swift, Al-Ko, Milenco, Witter, Camping and Caravanning Club, and Haymarket (What Car? and PC) - sorry if I've forgotten anyone! It is my aim to maintain my own integrity and I will say things how they are, not what any Manufacturer would want me to say, as I have absolutely nothing to gain by not doing so. When David Motton writes the article for publication, it is always a true reflection of the results (albeit at times some of the judges comments are tempered somewhat as they couldn't be published!). In doing the testing, we also have the wonderful benefit of back to back testing. At times, and driven in isolation, a vehicle may seem pretty good. Back to back either proves that it is good, or quite possibly the opposite.

 

[colin-yorkshire1]

hi Nigel,
while it is always nice to hear things from a different prospective and I for one do read the towcar reviews, it amazes me that the best towcar on paper is often not the best in practice, while the Dog that has everthing against it, comes out on top, so from a proffesional point of view, why is this!!.
my last two towcars demostrate this aptly, the previous one a Megane 1.9dti 80bhp towing a lightweight van (bailey) at almost 96% and just 25kg under the maximum allowed, towed the van superbly without any issues for more than 3 years, despite all the press reviews (2) and towcar comparison sites giving it the thumbs down, I will go so far as to say according to reports it was probably the worst choice I could have made, yet it was brilliant.
my present one a Meriva 1.7cdti 100bhp towing the same van at 74% and 950kg under it's maximum tow weight is nowhere near as good, it will not sustain a decent tow in 5th gear but is happier in 4th this caines the fuel economy and despite it's heavier weight gets pulled around with the van far more, yet reports have as a very good towcar for its class (towing vans 500kg) more than mine,
now we are not talking novice here, so what makes a good towcar!! .

 

[xtrailman]

Modern cars are generally higher geared, this plays a large part in the towing performance.
From personal experience with low profile tyres, yes you might get less side wall deflection, the the 225/45/17 profile tyres i had would tramline badly on the motorway, and the lowered suspension made it tricky towing off road.

 

[NigelHutson]

Hi Colin,
Obviously I can only speak about my own experience. I have towed for many years, and have been involved with the PC Tow Car event since its inception in 2007. As towing is only part of the final marks for this event, some cars that are brilliant as tugs lose out on practicality or What Car?'s opinions etc. Perahps the title "Tow Car Awards" might not be the most appropriate? I think David's intentions are to find vehicles that are excellent at towing, but are good all-rounders, bearing in mind that for the vast majority of us, little time is actually spent towing. But, when you do tow, you want it to be good. There have been some very interesting debates over the years as you can imagine.
Whilst I can't comment on your specific vehicles (I can't remember whether we've tested them or not - and if we have, then the fatc that I can't remember them means that they weren't bad!), there are some cars that I've thought were pretty good as towcars, but then they've lost out in other respects.
As Ray's previous post suggests, a lot of newer cars have such tall gearing (for solo economy) which hinders the use of top when towing. For example, the VW Passat 140 bhp used to be excellent in its class, but since the introduction of the "Bluemotion" technology across the range, it struggles when towing the ballasted caravan. The 170 bhp version though copes brilliantly.
I sometimes question towcar reports, and do wonder whether the vehicles have actually been used to tow, and if so, what have they towed. Again, I will give David Motton full credit, because he does test the cars whilst towing, and puts them through a pretty stiff test regime. That's one of the reasons that I'm very happy to be involved in the annual Tow Car event, because it's not simply a case of regurgitating Manufacturers' blurb. If it was, you can rest assured that I'd blow the whistle!
Nigel.

 

[Lutz]

I'd just like to point out that the title of the thread refers to stability, but replies are tending to centre around performance, which is a completely different issue. There are probably quite a number of relatively stable outfits that are rather sluggish as also good performers that are a pig to tow with.

 

[colin-yorkshire1]

hi Nigel, thanks for the reply, I dont think either of mentioned vehicles has been tested as both were manufactured before the awards started however the Megane was tested by someone (may be autocar) when the model was new and gave it a low rating.although somewehere else made it the car of the year.
but the main area one gets towcar info from initialy is usually outfit comparison sites, although I believe their predictions are based on data only and never actually test them, that is why the towcar reviews are so usefull. pity they only do new cars as it is a long time before some of us get round to owning one.
regarding Lutz's point, yes the thread may of strayed slighlty off track but there is binder, many things make a good tow car other than stability infact I would go so far as to say some modern cars would be inpractical in use had it not been for ATS,
surely the OP question was more to do with why a vehicle widely used as a towcar should be worse than the average run of the mill family estate. towing the same van.

 

[NigelHutson]

Lutz,
Colin had mentioned the performance of his vehicles, to which I was responding. You are quite right, there are some vehicles that might be steady enough but wouldn't pull the skin of a rice pudding, and vice versa (as I refered to in a previous post).
To get back to the OP, although they don't say which Freelander they're refering to (other than td4), I'm surprised that they've had issues, as the Freelander 2 is superb stability wise (let down in the past for practicality -small boot), and having towed with my father's previous 2002 Freelander 1, I/we never had any issues with that either.
I'd be making sure that there's adequate noseweight and that tyres are inflated to their recommended towing maximum first. My own car's handbook says that the tyres must be inflated to the fully laden figures when towing, up from 33/36 to 36/42. It does make a difference. When preparing for the Tow Car event, a whole day is spent on the tyres!
Could it be perceived stability? A car sitting lower to the ground with a firmer suspension may appear more stable than a 4X4 type with a more compliant suspension, but it might not actually be so. On the other hand of course it might.
Nigel

 

[ProfJohnL]

It is very difficult for the ordinary caravanner to quantify the degree of stability an outfit has, except when an outfit looses it completely resulting in a snake or worse. Most of us do not have access to the equipment needed to measure the forces and reactions to be able to measure stability.

What one driver may consider a small wobble, another might consider to be extremely unnerving. An inexperienced driver might react differently actually exacerbating the situation where as a more experienced or trained driver may be able to bring the outfit back under control. So relying on forum reports of instability is not an effective way to quantify the situation.

Designing a test regime involving several people all driving the same outfits does allow for a consensus opinion to be developed. But it also needs careful thought to how the outfits are set up, a standardised set of procedures is essential, such as loading, and road/track conditions, speeds. There is a debate whether the tests explore realistic loads caravanners use, or should they explore the extremes limits of the vehicles specifications????

Practical Caravan have explained the way they do tests. It may not be perfect but at least it is consistent, and that does allow readers to draw some meaningful comparisons.

Ultimately the choice of tow car is a very personal matter, every one has individual preferences which will colour what car or caravan you choose, so whilst PC may pronounce a particular model is towcar of the year, it may not match your individual criteria. However any cars or combinations that are judged by PC as being a poor match is more likely to be echoed by readers experiences.

 

[NigelHutson]

I couldn't have put it better myself Prof John!
Nigel.

 

[brian_c]

Just a bit nervous about jumping in on this thread because I don't have anything constructive to offer. I have followed all the replies to David's post with interest because I may have an opportunity to buy a Freelander 2 Diesel in November from a friend who has it as a company car.
It is not fitted with a tow bar yet and has been well serviced 4 year old in November. I am just concerned that David's post may raise doubts about the towing ability of the Freelander. However Nigel's post seems to endorse the Freelander.
I tow at the moment with a 2litre diesel Focus and a Bailey Ranger Max weight under 1200kg with no problems at all but am aware should I want to get a larger van in the future the weight if not the power of my car will restrict my choice and the Freelander made me think I could expand my options.
sorry if I am getting completely the wrong idea from David's initial post!

regards to all Brian

 

[NigelHutson]

Brian,
The Freelander 2 is superbly stable in my experience as one of the judges, and also when I've borrowed my Dad's 2009 version to tow our 1500 kg Lunar. The first time that I borrowed it, it compared very well indeed with our old Discovery 3 stability wise, and was a very strong performer to boot. Given the choice, I'd go for the auto (as Dad's) as it makes towing much more relaxed.
David hasn't clarified whether it is a Freelander 1 or 2, but my experience of both is very positive.
Go for it!
Nigel.

 

[brian_c]

Thank you for that Nigel. I know his is the manual version 2.2 but I am ok with that. Just got to hope his company don't decide to hang on for another year. He loves the car and even though it is a company vehicle he treats it as if it were his own only 42000 miles as well.
Regards Brian

 

[brian_c]

Duplicate post

 

[BaronsHuman]

Again thanks for the replies and the interesting discussion. The Freelander in question is a Freelander1 and is a great tow car and I would recommend anyone to consider. Neither of the incidents were close to a 'snake', and only provoked a quick lift off the throttle.

I suspect that both were a combination of loading and wind, but have always wondered if the mechanics of the vehicles had any influence.

David

 

[ProfJohnL]

Hello David,

Yes as I hope you will have understood from the posts the mechanics of the tow vehicle will affect the characteristics of the outfit, its more a question of how they influence it.

Every vehicle will be different, and some may be considered better than others. There is a general consensus that the Freelander does manage pretty well.

 

[NigelHutson]

The "incidents" may have been caused by road defects. If either the car or caravan was caught by the ruts we often see on motorways, that could cause a twitch. It might be that the tyres on the Freelander are more susceptible because of the tread pattern and/or sidewall flex than the estate car was?
Nigel

 

[RayS]

One factor which i don't think has been mentioned is the distance from tow ball to caravan axle.
Some years ago iIchanged from a UK made caravan to a German build. The overall van length was virtually the same but the ball to axle distance was significantly longer, due mainly to the longer tow frame at the front of the caravan which was designed to hold a bicycle rack.
The Germain caravan was significantly more stable under tow but the outfit had a larger turning circle.
It would be interesting to know if any of the cars tested in the TCOY event have been tested with more than one of the available caravans - perhaps the shortest and the longest to see if there is any discernable difference in towing performance.

 

[NigelHutson]

Ray,
The simple answer to you question regarding the Tow Car Awards event is "no". All the caravans are kindly provided by Swift, and are standard models from their ranges. As far as the OP is concerned too, it would appear to be the same caravan but with a different car.
I quite agree with you though, that the longer the A-frame the better.
Going back to the Tow Car Awards, the way that the caravans are ballasted means that each car is tested under the same circumstances, as in correct noseweights and where possible using the 85% figure (we'll not go down the pro's and con's of that route thanks, but that's what it is). Obviously there are some cars that cannot tow 85%, and then there are ones where Swift don't manufacture a caravan that can be ballasted to 85%. Nothing's perfect! As they are all tested under the same criteria, then whatever the length of A-frame, the poor ones will always be poor (although perhaps marginally better with a longer A-frame) and the good ones, good (again, possibly better with the longer A-frame). All stabilisers/ATC are removed from the test 'vans to ensure that it's the cars that are being tested, and any inherrant instability is not being masked by other devices.
Nigel.