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Snakes


Paul Dodd

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Has anyone else had a really terrifying snake occur even when using an Alko hitch stabiliser? I was towing at 55mph on a dry, clear, flat motorway - caravan well balanced to a Volvo V70 estate, no big lorries overtaking, no sudden moves on my part - when a really bad snake began for no obvious reason and lasted what felt like about 30 seconds until my ABS brakes brought it gently under control. The stabiliser has only "done" about 800 miles. Ideas, anybody?

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Hi Paul,

 

Firstly, let me say I'm sorry to hear of your experience. From your account, two thoughts spring immediately to mind. A trailer should be perfectly stable without a stabiliser fitted, and the ABS will only operate if you put the brakes on hard.

I am assuming both car and caravan are well serviced. Since you appear to have been towing at a reasonable speed in perfect conditions, the cause of the snake is most likely to be within the outfit. Recheck tyre pressures on caravan, tyre pressures on car should be set for full load, caravan noseweight correct, heavy items over the caravan axle (nothing heavy at the rear), weight ratio around 85% max.

Were there HGV ruts in the motorway? These can sometimes initiate a sway, but steer out of the rut and a correctly set up outfit will recover. Was there gust of wind to unbalance the outfit? Were you travelling downhill?

 

The brakes are the last thing you should touch if a snake occurs. Firmly hold the steering wheel straight and do not try to steer into the sway. Take your foot off of the accelerator and allow the speed to gently reduce until control is restored. If travelling downhill, the brakes may be used very slightly more than needed to prevent speed increase, but not enough to feel the outfit slowing, and certainly not enough to operate the ABS.

Finally, when a trailer is set up correctly and you have a matched outfit, a stabiliser may be used to damp out unexpected coupling movement. It should never be used to stabilise an unstable outfit.

Gordon.

Fourwinds Hurricane 31D Motorhome. Also MGTF135 1. 8i Roadster (fun) & Volvo V70 3.2Ltr LPG (everyday car)
Unless otherwise stated, my posts will be my personal thoughts and have the same standing as any other member of Caravan and Motorhome Talk.

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Hi Paul,

 

Firstly, let me say I'm sorry to hear of your experience. From your account, two thoughts spring immediately to mind. A trailer should be perfectly stable without a stabiliser fitted, and the ABS will only operate if you put the brakes on hard.

I am assuming both car and caravan are well serviced. Since you appear to have been towing at a reasonable speed in perfect conditions, the cause of the snake is most likely to be within the outfit. Recheck tyre pressures on caravan, tyre pressures on car should be set for full load, caravan noseweight correct, heavy items over the caravan axle (nothing heavy at the rear), weight ratio around 85% max.

Were there HGV ruts in the motorway? These can sometimes initiate a sway, but steer out of the rut and a correctly set up outfit will recover. Was there gust of wind to unbalance the outfit? Were you travelling downhill?

 

The brakes are the last thing you should touch if a snake occurs. Firmly hold the steering wheel straight and do not try to steer into the sway. Take your foot off of the accelerator and allow the speed to gently reduce until control is restored. If travelling downhill, the brakes may be used very slightly more than needed to prevent speed increase, but not enough to feel the outfit slowing, and certainly not enough to operate the ABS.

Finally, when a trailer is set up correctly and you have a matched outfit, a stabiliser may be used to damp out unexpected coupling movement. It should never be used to stabilise an unstable outfit.

Gordon.

Your suggestions are most welcome and sensible though I am aware of most of them - believe me I only used gentle braking because I couldn't slow down any other way. The outfit was loaded exactly as we normally load it and we have done long motorway journeys before without incident. Of course there might have been a rut but I think I'd have noticed even if on "autopilot". Tyre pressures all normal. Perhaps the answer is a motor caravan! We had a bad snake years ago on our first caravan and for that reason always used a stabiliser afterwards, but perhaps we're expecting too much of the device?
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Hi, I have to agree with Gordon on this one. Speed was not excessive. Nothing to induce the snake ie passing lorries etc. personally I think you are not running enough nose weight. A good matched and correctly loaded outfit can, without a stabiliser, can safely be driven at British speed limits. You should be able to induce a snake with the steering and if loaded correctly will just come back to straight without a problem. The stabiliser is just a belt and braces against external forces ie lorry, wind etc. Please note I am not saying you should induce a snake just that if you are a very experienced caravanner it would be possible.

 

ps personally I would not use brakes let it damp out itself. Unless you were going downhill or you have got to brake due to traffic in front.

 

Pete

Volvo
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Hi Paul,

 

This may be caused by the butterfly effect. A stable, normal condition can become unstable due to the effect of a very small or unperceivable force. Under certain conditions this small force is effecting something else in the ‘system’ which has a knock on effect. Before you realize what’s going on, you have a snake on your hands.

 

Just pray it doesn’t happen too often.

 

Lloyd

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Guest Hobbybod

Given that you have driven the outfit perfectly OK before, and that tyre pressures on the 'van AND car are OK, along with 'van loading and noseweight, then the build up of a snake is most likely due to some external factor such as:-

 

Intermittent Crosswinds

Regular road surface undulations. (Not on the A34 were you by any chance?)

 

or problems of wear in the 'van or Volvo, e. g.

 

Caravan suspension problem (I had to have a damper replaced on one side of my 'van.)

Worn rubber suspension on the 'van.

Incorrect 'van brake adjustment, e. g. one brake activating before the other, and or too rapidly.

If your Volvo has self-levelling, a problem there and/or in the rear shock absorbers.

An ineffective Alko stabiliser, due to contaminated pads etc. , although you shouldn't really get such a snake with the stabilser OFF.

 

BUT check that you really have loaded the 'van and car as before, and that the noseweight is not excessive.

This latter is a fairly common cause of towing problems as it overloads the car's rear suspension and lightens the front, affecting steering.

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If it was the M5 near Gloucester put it down to ruts in the road as that stretch of road is notorious for it.

 

I Don't know about the M5 iank, but I agree ruts in roads is a major factor for a lot of problems :(

Paul B

. .......Mondeo Estate & Elddis Avanté 505 (Tobago)

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about 3 miles south of M5 J11A (close to Brookthorpe - the Honda Pilots advert) there is a section of road on the southbound carriageway that goes on for about 1/2 mile of badly and irregularly rutted left lane. I pass this everyday in a normal car, occasionally in a westfield kit car (on wide semi slicks) and less often with the van on.

 

In all circumstances you are a passenger in whatever the happens to the vehicle you are in, if your try to correct, it makes it worse.

 

Just keep your speed low and let the vehicle follow the ruts if it wants to.

 

Gav

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about 3 miles south of M5 J11A (close to Brookthorpe - the Honda Pilots advert) there is a section of road on the southbound carriageway that goes on for about 1/2 mile of badly and irregularly rutted left lane. I pass this everyday in a normal car, occasionally in a westfield kit car (on wide semi slicks) and less often with the van on.

 

In all circumstances you are a passenger in whatever the happens to the vehicle you are in, if your try to correct, it makes it worse.

 

Just keep your speed low and let the vehicle follow the ruts if it wants to.

 

Gav

Hi all,

 

I too would put it down to the grooves in the road carved out by heavy traffic.

 

The circumstances described are typical.

 

Scenario is:- there is not much traffic on the road so you are not concentrating quite as much, merryly going along your way and suddenly the outfit feels unstable (the tyres have settled into the groove).

 

You steer to correct slightly with lttle response from your outfit, so you steer a little more firmly, the outfit heaves its self out of the groove and hey presto you have a snake on your hands.

 

your first reaction is to look for a HGV passing you, then you look at the trees to see if there is a coss wind,

there is neither so then start thinking in the imortal words of Sir Terry Wogan "IS IT ME"

 

 

If you are confident your outfit is set up correctly then "No its not".

 

Just make mental note to keep an eye on the inside lane for those tell tale ripples in the carriageway.

 

 

Hope this helps

 

 

Cheers

 

Steve

Jaguar E-Pace 180D HSE R Dynamic - 2008 Swift Conqueror 540

 

"Unless otherwise stated, my posts will be my personal thoughts and have the same standing as any other member of Caravan Talk"

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