Snaking

[Alex_5077321]

We recently picked up a new Lunar Lexon CS and set out to France for our yearly holiday. We are towing with a 2004 Automatic Mitsubishi Shogun. We've been caravanning for nearly 9 years, have towed with a Rover, 2 different landrovers and a chrysler voyager. We have always had single axle vans. We've always had van and car serviced regularly. So why did this new van go into very alarming snaking when towing at our usual just below 60mph. It came with an alko stabiliser, which creaked noisily, but we have been assured is fine. Later on in our journey it snaked again at 50mph and again at 45mph when we took it back to where we bought it from. We've checked the loading situation, that was fine, we checked the nose weight, that was fine too. We've checked the tyre pressure on car and caravan, so next we are off to check the car wheel tracking etc.

Anybody else got any more ideas. Or has anyone else got a lunar lexon cs they tow with a mitsubishi?. At the moment not sure if we want to continue caravanning as it was extremely scary!!

 

[Lutz]

For a start I would tow the caravan with a different car. By process of elimination you can then establish whether the car or the caravan is at fault. Assuming loads and load distributions as well as all tyre pressures are OK, I would suspect that the tyres on the Shogun have too much lateral compliance. That is a common shortcoming of 4x4's with relatively small wheels and high aspect ratio tyres. The problem would be aggravated further if it's a SWB 3-door.

 

[ProfJohnL]

Hello Alex,

It is not clear from your posting if the snaking occured on the same journey or after different stops where you may have moved items in the caravan or car.

If it was on the same journey, and the condition arose but at different speeds, I wonder if your outfit is particularly sensitive to rutting that some of our roads seem to develope when the surface is not repaired often enough.

Otherwise something else has changed, and I was surprised by a recent report from my garage that they have found a new caravan where the wheels were badly out of alignment, which made it very twitchy and difficult to tow.

In addition to Lutz's suggestions I would have the caravan axle checked.

 

[Alex_5077321]

For a start I would tow the caravan with a different car. By process of elimination you can then establish whether the car or the caravan is at fault. Assuming loads and load distributions as well as all tyre pressures are OK, I would suspect that the tyres on the Shogun have too much lateral compliance. That is a common shortcoming of 4x4's with relatively small wheels and high aspect ratio tyres. The problem would be aggravated further if it's a SWB 3-door.

Thanks for replying, sorry I didn't make things very clear, still a bit shaken up by the whole incident as you can probably imagine. We are still undecided about what to do next. Keep going over everything that has happened from the day we picked up the new van. We are in Exeter and the van came from Somerset, so we towed our old single axle luna lexon EB (7.2m long) with the LWB shogun up the M5 with no problem whatsoever. As soon as we were on our journey back I was watching the the new van in the mirrors, passenger side, and just happened to comment on how this new van seem to be moving around a lot more than the old one. So this would put the emphasis more on the caravan having a problem, I would have thought. At this stage the caravan was empty. On our holiday journey we had gas bottles stowed in the front locker, a jack under one of the front seats and a small fridge strapped in at the front of the caravan, at the back we had stowed 6 chairs, some wind breaks and a barbecue (all of which being the heaviest items we carry). As soon as we started the journey we heard a clanking, loud knocking noise which seemed to come from the stabiliser (which occured when moving fast or slow, but came and went). The snaking occured about half way to Plymouth as we overtook another car. We came out of the experience faily quickly and travelled to Plymouth at 50mph ok. Once off the ferry in France we had travelled for about an hour and half on single A roads (knocking noise seemed to come and go) and on a straight piece of road at 50mph we lurched into a another violent snake with no apparent reason. Again we recovered, quite quickly, but were very shaken. Continued to Campsite at 45mph. For the journey home with reloaded van with jack, barbeque and fridge in middle of caravan, travelled at 45mph, however, caravan did not feel any more stable and felt very lucky to have made it back in one piece. Our next outing was a trip up the M5 to take the empty caravan back, we travelled at 45mph, were feeling very nervous and on a bridge, a cross wind caught the van and it felt as if we were going to go again. (Knocking noise was absent this time, probably because the van was empty). Anyway, the supplyer has said they have now towed this van at 60mph with no problem, with stabilizer on and off. Bet they didn't drive it for an hour though.

anyway we now have to make a decision as to what to do next. As ours is such a long van for a single axle (7.26m)we are thinking of changing over to a twin axle avondale ranger or not tow at all!

 

[Ted2]

Sorry to be so negative but I might stop you wasting money changing your unit for others as we were persuaded to do..

We also had snaking problems with each of the 3 new caravans we had and we never found a solution.

The first was a Swift Corniche we towed with a Discovery manual. We were told this was snaking because it was a heavy unit to be on a single axle so we traded it in for a Conqueror twin axle towed by the same car. It also snaked regardless of what we did which included changing the tow bar, fitting a stabiliser etc.

This we traded for a Wayfarer twin axle and changed the Discovery to an automatic TD5. That was the worst combination of the lot. Despite we did not exceed 50mph it was so stressful to travel in it. Following a near disaster on the M1 we drove home at 30mph and sold both vehicles.

Now, 5 years later, we tow a Pennine folding camper with a Golf diesel automatic with no stability problems at all.

I know thousands of units sail serenely along the roads with no problems and I as found out the possible solutions are complex and will not be found in a dealers showroom.

As has been said, check the weight of your car and van are suiteable, check noseweight and load over the axles, fit a good stabiliser and keep your speed down until you are confident it is cured.

 

[Lutz]

In Alex's case I would follow John L's advice and have the wheel alignment checked. It certainly sounds as though it's not the towcar that's at fault, as towing the old caravan with the same car was not a problem. The clonking noise probably came from loose items inside the caravan flying around.

Certainly I would let someone competent have a look at the chassis of the caravan before going to the expense of swapping it for a twin axle unit.

Size and weight itself shouldn't be an issue. There are lots of single axle caravans in the 7-7.5m range and they can't all be inherently unstable or else word would have spread around by now. If you don't get any joy from your caravan dealer or from Lunar, I'd get in touch with AlKo (I presume it is an AlKo chassis). From what I've heard, AlKo are very helpful.

 

[BigAl1]

I also have problems of snaking at speeds of 55mph+. I had many near misses when travelling through france into Spain recently. I tow a twin axle Compass with a 2004 Shogun 3.5 auto. Tha van is loaded perfectly including noseweight. Car / van ratio is 80%, tyre pressurs are 2.4 barr but for no reason the van will go into a snake. Mild sidewinds make matters worse and passing lorries a nightmare.

I have noticed that if I approach speeds of 55-60 mph and "let my foot off the gas" the van will become unstable.

Any advise or info would be welcommed.

 

[BrianStAlbans]

Was there not an artical recently about imported Shogans having different towing limits to UK cars.Could this have something to do with the problem?

 

[Lutz]

I somehow doubt whether the towing limits would be different enough to be the real reason for the problem. From similar reports in this forum it does seem, however, that 4x4 owners are having disproportionately more problems with stability than car owners. I have indicated before that this may be due to the relatively high aspect ratio tyres that 4x4 vehicles usually have. They have walls with less lateral stiffness, making them very sensitive to sideways forces from the caravan.

Another reason could be the height of the towball. 4x4's often have a towball set higher than the 350-420mm specified in the standards (they are exempt from this ruling) and if the noseweight of the caravan was measured in the level condition rather than with the coupling at the actual height of the towball, the caravan will effectively have too low a noseweight when hitched up to the car.

 

[Rod_5041370]

You don't say what tyre pressure you are using. I tow a 7.37m, 1600kg, single axle caravan with a Landcruiser and a Toyota Surf without any stability problems but the makers stated tyre pressure is 4.5 bar which I believe is circa 70 psi. Are your tyres at the makers recommended pressures?

 

[Royston]

Alex

The First van that I owned,I took the advise of a friend to get the vans wheels balanced prior to towing,I also did this on my present van, never had the slightest problem.

I agree with the thoughts of both John L and Lutz with regards that its the van and not your car.

 

[ProfJohnL]

For Alan (23 Aug 2005 11:52 PM)

I have no definitive answer to your problem, but playing devils advocate - tow at a speed where the outfit can be safely controlled. If this means 55mph then so be it.

In fact if you tow at a speed where your outfit becomes unstable, then you are breaking the laws because you're obliged to keep your vehicle in a road worthy condition. If its unstable, then by definition it is not roadworthy at that speed.

There is no rule or law that saws all outfits should be able to tow at the legal maximum speed, so may be there is nothing wrong, except your expectation that you can tow at a higher speed.

There are some good sensible tips in this thread so give them a try, but do watch the tyre pressure one carefully. Never exceed the maximum pressure the tyre manufacture moulds into the side wall of the tyre, Rod's 4.5Bar (70psi) seems rather high.

 

[Lutz]

Every vehicle towing a trailer has a critical speed above which it is liable to go unstable. This critical speed is specific to each outfit and is dependent on a number of factors (weights of car & trailer, tyre equipment and pressure, polar moments of inertia, etc., etc.) For example, in the comparison test of the VW Touareg and Merc M that I mentioned elsewhere in this forum, these speeds were 98 and 97kph, respectively (both with the same trailer). For the purpose of the test, the weight distribution was intentionally set to simulate a poorly laden caravan. With optimum weight distribution, these critical speeds will, no doubt, be signifiacntly higher.

 

[Rod_5041370]

4.5 bar tyre pressure.

My caravan was new in May 2005 and there is a plate on each wheel arch stating 4.5 bar.

Tyre pressures of 60psi+ are not unusual for modern single axle caravans.

Twin axles are normally much lower pressure, I also own a 7.7m twin axle where the stated tyre pressure is 2.5 bar.

 

[ProfJohnL]

4.5 bar tyre pressure.

My caravan was new in May 2005 and there is a plate on each wheel arch stating 4.5 bar.

Tyre pressures of 60psi+ are not unusual for modern single axle caravans.

Twin axles are normally much lower pressure, I also own a 7.7m twin axle where the stated tyre pressure is 2.5 bar.

Accepted Rod.

But not all tyres will be rated to that so I stand by my advice to check.

 

[John_5078188]

I have experienced similar problems with my new van.

We bought a new Ace award (24ft Ext)in January - at the same time we traded in our old 2.5D Jeep grand cherokee for a 4.7 V8 model.

Our old caravan was a 18ft (ext)towed without a problem with the older bull dog type stabiliser. The new van is a nightmare even with the more powerful Jeep. I am now in the process of fitting a bulldog to the new jeep and van to assist the Alko stabiliser. We have tried everything. The tow ball has been lowered, the caravan towed empty etc... but noth seems to improve the stability and regular snaking - therefore - two stabilisers. i will let you know how it goes.

 

[Lutz]

Two frictional stabilisers acting in tandem is not recommended and could invalidate the warranty on a new car.

Here we yet again have a 4x4 with stability problems - in comparison, very few reports in this forum ever mention similar problems when towing with saloon cars and estates except when something is seriously amiss.

I expect that a significant improvement would be gained by fitting bigger wheels with lower profile tyres on the towcar.

 

[hymer]

John,

Sorry to hear of the instability problem you are having. Perhaps what works effectively for me may give you some lines of inquiry...

I tow a Hymer 545 caravan (23 ft ext length, single axle, approx. 1500kg laden) with a Mercedes ML270 4x4 and have never experienced any instability. Have towed for 2 years now in wet and dry conditions, at up to 65mph where conditions permit and have been overtaken by/have overtaken lorries and coaches at speed without problem.

The Merc has standard manufacturer-fitted Continental tyres on 17" wheels inflated to 32psi all round; you may have the same combination since the Jeep and Merc are both from the Daimler/Chrysler stable. The Hymer has an Al-Ko 2004 stabiliser, sits level on the towball and I set the noseweight to 100kg. The caravan is fitted with shock absorbers as standard, which I have noticed seem to be absent from most British manufactured caravans. Maybe the shock absorbers are a factor in the stability of the outfit.

Rather than fit "bling" wheels to your Jeep, perhaps you could locate a dealer willing to let you try out another make/model of caravan for comparison with the Ace?

Mike.

 

[Lutz]

Certainly shock absorbers on the caravan are a positive contributing factor. It is not without reason that they are a requirement in Germany to be allowed to tow at 100kph (subject to other conditions being fulfilled, as well). Without them, the speed limit is 80kph.

 

[Caroline3]

Goodness you lot don't seem to be having much luck with the snaking,but we tow a 7.3 metre Elddis Avante with a Volvo V70 and it seems more stable than our last little 2 berth compass ralley The new van has a winterhoff hitch lock/ on it and we have recently towed 3000 miles around France and the van stayed as stable as a rock. I know I am not very technical about these things but the winterhoff certainly seemed to make a big difference to our towing stability.

 

[ProfJohnL]

Goodness you lot don't seem to be having much luck with the snaking,but we tow a 7.3 metre Elddis Avante with a Volvo V70 and it seems more stable than our last little 2 berth compass ralley The new van has a winterhoff hitch lock/ on it and we have recently towed 3000 miles around France and the van stayed as stable as a rock. I know I am not very technical about these things but the winterhoff certainly seemed to make a big difference to our towing stability.

Hello Caroline,

You say the Winterhoff has made a big difference, but have you actually tried to tow the outfit with the standard hitch supplied with the caravan?

 

[Lutz]

John,

Sorry to hear of the instability problem you are having. Perhaps what works effectively for me may give you some lines of inquiry...

I tow a Hymer 545 caravan (23 ft ext length, single axle, approx. 1500kg laden) with a Mercedes ML270 4x4 and have never experienced any instability. Have towed for 2 years now in wet and dry conditions, at up to 65mph where conditions permit and have been overtaken by/have overtaken lorries and coaches at speed without problem.

The Merc has standard manufacturer-fitted Continental tyres on 17" wheels inflated to 32psi all round; you may have the same combination since the Jeep and Merc are both from the Daimler/Chrysler stable. The Hymer has an Al-Ko 2004 stabiliser, sits level on the towball and I set the noseweight to 100kg. The caravan is fitted with shock absorbers as standard, which I have noticed seem to be absent from most British manufactured caravans. Maybe the shock absorbers are a factor in the stability of the outfit.

Rather than fit "bling" wheels to your Jeep, perhaps you could locate a dealer willing to let you try out another make/model of caravan for comparison with the Ace?

Mike.

Although both the Merc and the Jeep have 17" wheels and even if they had the same tyre equipment, that does not necessarily mean to say that the lateral stiffness of the whole vehicle would be the same. If, for example, the suspension has more compliance (and I would expect this to be the case with a US car in the interest of a softer ride), there could still be a big difference in towing stability between the 2 cars. Unless there is opportunity to stiffen the suspension (and I mean sideways not vertically) by using harder bushings, larger wheels and low profile tyres could improve the situation by offsetting the shortcomings elsewhere, such as in the suspension.

 

[martin_5079083]

I'm no expert but could it be a break problem - Not sure how the hand break on a caravan works but it may be worth checking that one of the wheels is not trapped or partially trapped by the break.

Probably totally wrong and the breaks can't jam up but the van that lost it when you stop accelerating did sound like a similar problem I heard in a light machinery trailer a friend was pulling - It took them ages to figure that one out, as the trailer was new but faulted

As some one who is being nagged by his wife to get a caravan I think I'll be requesting a try before I buy option just in case.

Martin

 

[Lutz]

If the brakes were binding, exactly the opposite is likely to happen, i.e. the caravan would actually be less likely to go into a snake until they overheat and fade. You would then be left with absolutely no braking performance from the caravan and the car's brakes would have to do the whole job of slowing down - another potentially dangerous situation.

 

[littleangel]

Hi lex,

We have changed our car to mondeo, snaking none, previous car vectra snaking did occur. some are good and some are not so good I think.