Snaking with stabiliser

[Surfer]

I drive a Volvo S80 D5 kerb weight 1535 kg and tow a 2004 19 foot Lunar caravan with a MTPLM of 1350 kg. The caravan is fitted with an Alko stabiliser and the Volvo has a Volvo fitted detachable tow bar, however I am having a major problem with snaking. I have checked the wheel alignment, balancing and tyre pressure on the car and caravan and also fitted new tyres on the car, but the caravan continues to snake.

Last Friday, I collected the caravan from the dealer and was on my way south on the M5 when just after I had overtaken a slow moving truck, and travelling at a speed of about 60 mph, I indicated to pull into the nearside lane when the caravan began to snake violently, so much so, that I was all over two lanes. I allowed the car to slow down a bit and then accelerated and the caravan stopped snaking. Earlier I had overtaken other high sided trucks and also other caravans and no problem. This shook me up so bad, that I insisted the dealer come and collect the caravan from the site south of Gloucester which they did.

I have had it occur when there has been no other traffic around, i.e. travelling on the M50/A449 south or north. It always seems to occur when travelling at about 55 - 60 mph and comes up suddenly on you without an sort of warning.

I am desperate and would appreciate any input from others who have had a similar experience. The dealer is trying their best, but the problem is very random and intermittent which makes it difficult to trace.

 

[Lutz]

I would strongly assume that the noseweight was way too low or load distribution in the caravan itself was poor.

 

[woodsieboy]

Hi Ian , there are parts of the M5 around south Gloucester on the southbound carriageway that seem to be rutted from heavy lorries, it can cause problems when driving without a caravan in tow, I drive this road 2 or 3 days per week, so with a caravan on the back I presume it will be worse.

 

[OldBean]

Ian - is your tow ball Alko compatible - they need a different type of towball. If your volvo towbar was pre-fitted before you got the caravan with the Alko stabiliser it is possibly not the correct type - ask your dealer to check. If the towball is wrong then the stabiliser would not work at all. You can buy Alko compatible towballs from most dealers. Just a thought, from a very non-techie!!!

 

[DavidMiller_5040289]

Also make sure that you have the correct tyre pressures.

 

[Ian_5040859]

There is no problem with the load distribution and the noseweight of the car is 75 kg and the van about the same. I could put it down to the road surface but the M50/A449 has been resurfaced recently and it happened on that road but not as bad so I think we can rule that one out. The dealer had the car in and everything has been double checked including tyre pressures and problem. At present when towing my rear tyre pressure is at about 2.5 bar which is about .5 bar below the pressure one would normally have if the car was fully laden with 3 adults in the rear. I am running out of options.

 

[PeterT]

Get a very independent engineer to thoroughly check the Lunar chassis for distortion. It might have been distorted when over-tightened down on the transporter, or may have been actually dropped off the transporter, rather than ramped off.

I have a friend whose three (rpt) three Lunars suffered this way (the 2nd and 3rd were 'guarantee' replacements). The third has been disposed of, he now has a Compass. I too have sold my Lunar.

 

[Lutz]

After having gone through all other options, including Peter's recommendations, if you're still left with a snaking problem, fit an electronic stabiliser. I've had mine now for a couple of weeks and it gives me absolute peace of mind. It cuts any snake dead.

 

[Lutz]

You say that you set the rear tyre pressures about 0.5bar below the recommendation for a fully laden vehicle. I would suggest that, as a first measure, you should, when towing, increase the pressures in the rear tyres to the fully laden value, regardless of whether you are actually carrying the full payload in the car or not. That should help. Also, if the back of the car was empty at the time, this could account for at least part of the problem. The general rule that the heavier the car in relation to the weight of the caravan, the steadier the combination, always holds true. Maybe if you load the boot with a nice big sack of potatoes or something of equivalent weight, the handling characteristics will improve.

 

[henryford_5041053]

75kg sounds a bit light for a van of this size. I agree with Lutz - it sounds like it's not loaded safely.

 

[mike_5041102]

Why have you not tried towing the caravan with a different car ? That will tell you if the problem lies in the car or caravan. I had a similar problem, cause was eventually put down to tyres that were virtualy new and possibly incompatible with regard to spring and shock absorber characteristics. Changing the tyres for those recommended by the car manufacturer solved the problem.

 

[ProfJohnL]

Hello Ian, The stability of an outfit is dependant on a large list of caracteristics, some of which you have control over (Nose weight, pay load, speed tyre pressure etc.) and some that you don't (Complianse of the suspension, over hang dynamic wind resistsnace, direction and speed of wind road surface etc). It is dependant on the mix of charateristics being right. Sadly it is concivable that a particular combination of car and caravan will be inherently unstable, and may remain so regardless of all the add on featurs or weight distribution. Firstly I note that you are running your tyre pressures 0.5Bar below the fully loaded maximum for the car. Towing places an emence additional dynamic load on the car. Dont forget that bodies in the car sit between the front and rear axle, so the load is shared, the caravan nose weight sits well behind the cars rear axle so it has a greater effect than a simple body count. I am sure you should be running the tyres at the maximum permitted. May I suggest that you try to borrow a friends car to see how it tows with your caravan. This may clarify if the caravan is particularly sensitive. In addition try redistributing the load within the caravan, Try to keep heavy objects near the axle, (gas bottles must be kept in the proper locker)I would be surprised if the Volvo can't match you van so I think there must be something that you are doing that may be a major factor in teh instability.