Towing - Snake/Wiggle Sensation

[Ricey]

I've towed our caravan a few times now and experimented with different loads, load placing and noseweights, but each journey I experience a slight sensation of snaking/wiggling when I reach 50-55mph.

It's not a dangerous snake by any standard, but it feels like it could develop into a bad snake if I was going any faster. The tyre pressures on the car and van are as specificed and checked with the foot pump gauge and a seperate pen gauge. The payload is usually between 220kg - 260kg (300kg allowed) and I have varied the noseweight between 60-75kg by moving items such as the awning (35kg) from the front dinette to across the axle. I've weighed everything I put in the caravan and made sure that the weight is balanced equally on each side. I don't have any onboard water tanks or underslung spare (spare carried in the car boot).

I have a 21ft, single axle, 6 berth, Wilk caravan and wonder if it is possible that it's the van's fairly flat fronted design which is causing the sensation and would welcome the Forum's thoughts.

Thanks,

 

[Lutz]

You don't say what you are towing with or whether you have used the same towcar together with other caravans in the past. If so, what was your experience with them? I ask because the not only could the caravan be the cause of problem (although you have described all the measures you have undertaken to prevent that), but also the towcar. Cars with lots of lateral compliance in the suspension are more likely to lead to some degree of instability. The cause could be the suspension itself or the tyre equipment, even if the tyre pressures are according to spec. For example, tyres with a high aspect ratio, as often fitted to 4x4's, are more liable to promote instability. In this case, raising the tyre pressures slightly over the recommended values could help alleviate the problem slightly,
One question I do ask concerning the caravan, however, is how sure are you that you have a 300kg payload allowance? Have you measured the unladen weight of the caravan to confirm the MIRO figure?

 

[Ricey]

Hi,
I'm towing with a SAAB 9-5 2.2TiD, running on 225/45/17s unfortunately i haven't towed anything else with this car. I did tow the van with an Isuzu Trooper once, but this was the first time I towed and it was for a relatively short distance so I didn't have anything to compare with and I don't think I even got up to the 50mph mark.

I will try upping the tyre pressure on the car next time out to see if that makes a difference. I haven't checked that the MiRO is correct, I was just going by the handbook and aiming for an 80% towing ratio as a tower with limited experience. To be honest I hadn't even considered that the MiRO wouldn't be correct. Certainly something worth checking.

Cheers,