Trailer Instability

The load is not properly positioned on the trailer. You may need to move the CG forward to put some more weight on the tongue and hitch.

The other problem may be trailer length that is longer the tow vehicle length.

Good luck.

The weight distribution is wrong move more weight to front of trailer I had similar problem when i started to tow a caravan I put more weight forward in the van problem solved

Cheers

peugeot man

On a long shot basis (but easy to do), I would check the type of tires that are on the trailer. Mixing brands or weight ratings can sometimes cause problems. Next up would be tire pressures. I would also check the wheel alignment as a last resort because the most likely cause is as mentioned, the load is too far back and you need to bring it forward a bit. Check the hitch loading regulations for your type of hitch. I think a your hitch weight should be closer to 150 kg than 70 kg.

Underinflated tires on tow vehicle. Radials/underinflated on trailer. Less than 10% TOTAL towed weight on tongue. Worn shackle hangers on trailer. RE: Sprinter Towing Capacity For the 06 and earlier 2500 (4 wheeler) and 3500 (6 wheeler) model Sprinters, max towing capacity is 5000 pounds. For the 07 model 2500, it's still 5000 pounds. For the 07 model 3500 it's 7500 pounds.

GA

10% is the magic number.

2.7 tons should be 270 kg on the hitch.

If 'attitude' problems manifest - fit spring uplifts to the rear of the tow vehicle. Air bags are a good option.

The most common reason a towed trailer will start to oscillate from side to side is center of gravity of the load on the trailer.

Under-inflated tires can exaggerate the problem but will not cause the problem. With a load properly situated on a trailer, the tires can go completely flat and not cause oscillation.

The center of gravity of the load must be forward of the center of the axle or axle set to remain stable in transit. This simply means more weight has to be forward of the axle than behind it.

This is likely the best answer so far. As someone who has been towing a wide range of trailers of every description with loads varying from 1 ton to 100 tons ( not a misprint ) under almost any condition you can imagine in Alaskan conditions I can tell you that a well balanced load is perhaps the single most important factor in determining just what you might get away with in pushing the envelope. Balance the load with appropriate tongue weight and then tune the system.

Good luck.

GA

Thanks for the commonsense.

As others have said this is a center of gravity problem and the CG being wrongly positioned causes small excursions to be amplified by the excursion they cause.

The best way to fix is to adjust the CG forward to eliminate this. You can also add a shock absorber that introduces loss into oscillation process, damping it out. There are also products sold for this use.

more about the problem and the cure here

Your problem is essentially to eliminate flexure in the flexible mechanical components connecting the rigid mechanical components to the road surface.

First check the tyre numbers ( axles???). Tandem axles?? Correct trailer tongue weight? Load levelers?

Load balancer springing? Lateral (roll) stiffness and spring flex are factors which are not given enough attention. Tyre pressures? They should be at the maximum stated on the sidewall, both for the towing vehicle AND the trailer. This reduces the amount of flexure and thus the steering effect of deforming tyres. Are the tyres actually up to the job? What is the rating? You may need to go to a higher ply rating on the trailer tyres than your Sprinter. Are you using Sprinter compatible wheel assemblies to have commonality in spares?

A lot of trailers aren't actually 'designed'. They are too often made to a style which began waaaayyyyy back and now gets everyone in trouble, such as yours.

I always use high rated automotive springs, because the leaves are wider affording greater lateral stiffness and resistance to deformation when in roll-steer. Add a Panhard rod if you can't upgrade the springs. The bonus is that my trailers give a much softer ride to the load than commercially available units.

The axle(s) bump and rebound geometry should be set so that roll-steer is cancelled.

Have trouble visualising all this?

Get a competent friend to drive the rig and you follow closely behind, with you trailer designer, observing.

Cheers, see how you go,

Stu.

Hi HughMattos,

Basically you can't do anything to resolve the issue with the current kit. You would need a much heavier truck to achieve a higher speed. Anyway I'm not sure just how reliable the braking performance would be at even 30MPH let alone the 40+ you are doing.The oscillatory motion to whish you refer is not purely side to side there is a rotative component present which is caused in part by the interaction of the suspension characteristics of the two vehicles.

There are things to assist in the resolution of these forces which were available some time ago and were used by the caravan towing fraternity.These took the form of small hydraulic dampers introduced alongside the drawbar and connected at an angle to towing vehicle.

Again this cannot be considered a 'one size fits all' solution as the oscillatory process once established will overcome these stabilisers and assuming you were at a higher speed before the on-set of the motion things would get much worse very quickly and put you out of control.

I note your location and the topography of that county is ideal for causing trailer related problems. Recently I was following a 2 axle horse box behind a Landrover across rural Lancashire, he was trying to 'get along smartish' and every little while the trailer would start weaving and he would slow down until things calmed down. I kept my distance as there wasn't a chance of overtaking , and sure enough on a short downward slope it happened. Weaving followed within seconds by pitching as the gyratory forces took over,result horse box on its side against a muddy verge,draw-bar 4 feet in the air and Landrover still attached with its rear wheels in the air.

Although the 2 lane road was busy luckily no other vehicle was involved. The driver and mate scrambled out and went round to the rear of the 'box' and released 4 mature bullocks who took off in all directions!!. I reckon he had topside of 2 tonnes of beef on-board and it clearly was overloading the towing vehicle.

I also note your comment on increasing the drawbar down force, other than compressing the tow truck's rear springs (in the static condition) I would still say that the dynamic condition would not be improved enough to justify any increase in towing speed.

It was a daunting thing to be in close proximity to that horse box but I would hate to see a heavy object like your digger coming asunder from the trailer on a 'Devon Bank'!

Good luck

Massey.

Most of what you wrote was bsolute rubbish. You don't any useful or helpful knowledge on this subject at all, in fact, some of your advice could even be considered dangerous!!

He must simply move his CG forward till the problem is resolved....

The brakes are automatic, either mechanical or electrical and if working correctly, they add remarkably less distance to the normal braking, but he should be aware of this and not to follow trucks and cars to close...

Andy,

Come on, don't sugar coat it. Speak your mind.

I tend to agree with you. It is better sometimes to remain silent and appear unknowing, than to.............................you get the picture.

Can't say I've always followed that advice myself.

LOL

What he gave was a flawed opinion that could be dangerous, nobody should try increasing speed to stop a trailer oscillating, as I said before somewhere, it just adds to the kinetic energy to be got rid of.....eventually.

The accident he saw was a typical result of NOT braking properly......

I must admit years ago, the first time it happened to me, I had read all the advice and for a few milliseconds I was deciding whether or not to actually put it into practise.

My wife was so struck dumb she could not utter a sound (now thats a first!!) Its tempting to do it more often on that score!!

BUT, I followed the advice and braked b"firmly" and it "tamed" the caravan within a half of a cycle.......my caravan has twin axles, but according to the advice, the number of axles does not play a role, it works on both......

It was so bad that time, that I could only steer a relatively straight path by steering wildly left and right, which was otherwise not helping at all.......

I was driving to overtake someone on the A1 going north in the UK, that slowed to 40MPH every time it was a single lane and speeded up to 60MPH when it was dual carriageway......I was doing about 90MPH when the oscillation started.....allowed is 60MPH in the UK for a caravan.....completely my fault (but it did quieten the wife down!!)

Any towed vehicle which won't maintain the speedlimits shouldn't be allowed on the road.

We produced a new monocoque GRP RV trailer and designed the suspension so that it would tow at 100mph fully laden, maintaining the posted advisories in all corners and bends. It surpassed all expectations under test. It is 2800kg GVM and towed by a VW 'toerag'. Suspended over a tandem "axle" layout, independent semi-trailing arms sprung on airbags, with tubular dampers.

In this particular case, I postulate that the trailer is a POS to start with and that it's grossly overloaded for second.

No amount of moving CG or stuffing around will fix either problem.

Flick the thing off, and trade up to a rig that is DESIGNED to perform to specs. Or, at the least, have the trailer modified to safely carry the weight.

A decent prang will effect many lives, not just that of the driver.

Stu.

You could never sell a car in the UK called a "Toerag" as this is an uncomplimentary name for a person you don't like in the UK....seemingly not in Oz.......

The proper name is "Touareg".......

Don't take it to heart Andy.

It's called that all over the UK and the nickname has invaded here too.

Promoted initially by one other than J. Clarkson Esq. in his worldwide aired TV show.

Don't blame me.

I know it's called a Touareg. It was so to indicate it's superior off road capabilities.

Just like the desert dwellers it was named for. But it sort of missed the mark a little.

Hence the nickname.

I guess there is a subtle inference there too in the 'Volkswagen' maker's name. But that's just the other end of the scale. It is certainly no 'peoples car'.

And I don't apologise.

Fort what?

Cheers,

Stu.

I made a statement, I did not ask for an apology. Thats up to you and your lack of manners! I don't take such things to heart.....

I just thought you couldn't spell I really only thought that and wanted to let you know that this was a derogatory term in the UK (which you knew it would appear!)

So the Joke (thats a joke, get a life!!) was lost on most/many people who do not live in the UK, which is probably over 80% of CR4 users......if not more......

Some very good answers so far, my contribution is, to observe any articulated Truck and Trailer for inspiration . The axles are allmost as far back on the trailer as is possible, This is how I make trailers myself for a great variety of purposes ,and my own car transporter will tow at a very illegal speed with total stability, The Articulated Truck Trailer that I used as an example is extreme of course , Set the axles back until things improve then add some more. This is how I arrived at the best solution for my own Trailers.Dont be afraid to put weight on the rear of the towing vehicle , the 70 KGS you mention is too little. A 4x4 Jeep would solve your problems too.

Its always best to tow with an ABS/ESP equipped tow vehicle, it really helps in bad situations.

If you ever get the oscillation at higher speeds again, once you have corrected the CG as many have already correctly mentioned, do not hesitate to brake firmly, this will stop the oscillation immediately. It used to be taught on AA road training and used to be on their website, I could not find it today...

Many ignorant people will tell you to accelerate, don't ever do this, you are putting even more energy into the problem.

All the authorities on towing and this dangerous oscillation, all say that braking firmly, but not an emergency braking, fixes the problems.....

I also tow a caravan (and trailers and car transporters even occasionally!) and have handled such problems with this good advice, time and time again as I tend to drive a bit too fast and then find a great crosswind........

I probably brake too early nowadays after a couple of almost bad experiences.....as soon as the swaying starts......that way it never gets dangerous and is a warning to me that I am not driving correctly for the conditions.

""I tow a 2.2 tonne digger on a 600kg four wheel trailer behind a 3.5 tonne Gross Vehicle Weight, 5.5 tonne Gross Train Weight Mercedes Sprinter van. I set the draw bar down load at 70kg.""

After reading the comments, it appears that the digger does not act as a point weight, and thus has a high polar moment of inertia...with the heavy digger instrument being the tail that wags the dog. If you could articulate the arm so that it was reaching over the digger backwards it would reduce that moment.

Make sure that this does not make any height problems for you on any bridges you may pass under.

I have seen the digger portion taken off the end of the arm and stowed close to the cab.

I wonder if your "digger" is what we call a front end loader?

I looked on the ADAC Germany's website, there it was easy to find, in an article, this was printed in large print (for those who can read German!):-

"Weder Gegenlenken noch Gasgeben: Beim Pendeln hilft nur starkes Bremsens"

I would translate this as follows:-

"Neither steering against, or accelerating: By oscillation helps only strong braking."

I have translated it exactly, which is Grammatically incorrect in English.

It is SO true....but until you have the guts to try it out, you may find it hard to believe!!

The complete article in German can be found here:-

http://www.adac.de/search/GSA_searchResult.aspx?access=p&client=default_frontend&ie=UTF8&num=10&oe=UTF8&output=xml_no_dtd&FormID=master&q=anh%C3%A4nger+fahren

Click on "03. Zug-Nummer", its a pdf....

"I tow a 2.2 tonne digger on a 600kg four wheel trailer behind a 3.5 tonne Gross Vehicle Weight, 5.5 tonne Gross Train Weight"

2.2 tonne digger + 3.5 tonne Sprinter + 0.6 tonne trailer = 6.3 tonne MAM (Maximum Allowable Weight) Gross Vehicle Weight which is ILLEGAL as you are exceeding the GVW

This is overloading

Tony

UK & USA are different in many ways, this is one of them.......I believe he is legal in the USA.....if he is in the USA!!

I agree that there are differences between USA and UK.

My understanding fails at Gross vehicle weight being less than the total weight that is being towed.

To me, Gross means maximum.

What would be meant by Gross Vehicle weight? Taking the OP, how much more would he legally be allowed to tow?

Greetings.

Check to see if you have tow-in in the front axle.

If you don't this is probably your problem.

If you don't you can cut the axle part way on the back side of the axle. Use a come along to pull the axle back until you have about 3/8 inch tow-in and then weld it back up. Or you could go to a shop and have them do it.

This is how a major Horse Trailer manufacturer has made their horse trailers for years.

An old cow poke told me that was why my horse trailer pulled at 60 mph behind my truck loaded with horses was a smooth as could be and the one next to me wandered all over the road at 45 mph. He used to work at the factory and had hauled horses and livestock for over 50 years.

Hope this works. I owned another brand that didn't have any tow-in and it was miserable.

The love of money is the root of all evil and putting tow-in in an axle means usually it takes a far more expensive axle to provide tow-in and you guessed it they didn't do it.

Thank you to all for your helpful comments.

Yes the loading situation is not ideal, towing a digger and trailer behind a vehicle - which does have ABS and Traction Control - with a 2 tonne towing limit is not ideal. I remove the buckets and all heavy items from digger into the van to increase the load on the van rear axle, and to reduce the combined mass of the trailer.

All tyres - van and trailer - are pumped to max allowable pressure.

I try to use the digger hydraulics to lift the digger mass off the tyres to reduce the secondary flexibility between the digger mass and the trailer. However, this does raise the CofG by probably 10 cm.

I will try putting more front end load on the drawbar, but I do have to be mindful of the vehicle tow bar design spec.

I am interested in the comments on tyre types. My trailer has 165 X 80R13 tyres on two axles. I note that more expensive digger trailers now use three axles with 195 X 50 R13 wheels and tyres which gives a very much lower ride height and much smaller sidewalls. Does anyone have experience with these newer trailers.

I am interested in the physics of the front axle tow-in theories. The trailer has the rubber torsion beam axles mounted solid to the chassis frame with no shockers. Before I get the workshops to cut and weld the axle does anyone have any comments on the science of how toe-in on the front axle may affect stability?

Any further comments would be appreciated.

My personal take is that the manufacturer has already taken "toe in" into account.....

Any "Cut & shunt" work, may make the trailer really dangerous. At best, you will get increased tyre wear.....at worst - who knows.

I have towed tandem axle trailers for many, many years. With the right balance (it can be a matter of a few inches) they tow well. I have even towed with overload.

My caravan has as good as no nose weight while static and tows like a champion, verxy stable, it only gets to sway from driving far too fast and/or cross winds.....