Tongue Weight in the UK: 5%-to-7%

[DavidNJ]

The paper: An experimental investigation of car-trailer high-speed stability

This is from the University of Bath. It is on point but didn't test with a WDH. They looked at tongue weight (they call it nose mass), trailer mass, moment of inertia, tire pressure and axle position. These are the folks who made some of the 'model car on a rolling roadway' videos.

Interestingly, the percentage tongue weight they tested for was -0.8% to 10.5%. They found "an increased nose mass improved the system stability, although the improvement becomes less significant when the nose mass rises above 6–7 percent of the total weight."

Another finding: "when the trailer inertia increases, the damping of the combined car–trailer system decreases dramatically. The inertia effect suggests that, when a driver is loading a caravan, the mass should be placed as close to the centre of gravity as possible in order to minimize the resulting increase in inertia."

Their conclusions:

CONCLUSIONS
Very little work has been published on the experimental measurement of high-speed car–trailer stability. In this study, extensive experimental measurements were carried out on a combined car–adjustable-trailer system. By adjusting the trailer settings, the effect of different trailer parameters on the system stability was examined. It was found that the dominant factors affecting stability were the trailer yaw inertia, nose mass (load distribution), and trailer axle position. The tyre pressure also affects the stability, although the effect is less significant. It is interesting to see that the trailer mass alone does not dramatically affect the stability; however, as a heavier trailer normally has a larger yaw inertia, a limit should be placed on the relative car–trailer masses.

A friction stabilizer is shown to be helpful in improving the system stability, although in these tests the stability was not increased hugely. In addition, high-speed towing tests were carried out on cars fitted with an ESP which automatically brakes individual wheels and controls the engine throttle position should the vehicle dynamic response differ from that expected. These tests demonstrated that, if the dynamic response ‘error’ exceeded a preset threshold level, the ESP operated and the highspeed stability was improved by controlling the car yaw oscillation associated with trailer instability.

This begged the question: what is the noseweight standard in the UK? Answer: 5%-to-7%. And they don't seem to be picky. They basically say it is the 5%-to-7% or constrained to the lowest of what the tow vehicle, hitch, or trailer is rated for.

These are two articles and a video:

How to measure and adjust your caravan’s noseweight

Caravan Club Leaflet: Noseweight

 

[DavidNJ]

Interesting...Airstream in the UK has 3 models. They all have a 150kg hitch limit. The biggest has a Maximum Technical Permissible Laden Mass (MTPLM) of 2400kg and a Optional Upgraded MTPLM of 2680kg. They represent tongue weight percentages of 6.25% and 5.60%. Max.

 

[Johnvan]

I’m pretty sure weight distribution hitches are illegal in Europe so the trailer axles are further forward to reduce the tongue weight.

Do an image search for “caravan Europe “ and you’ll see a lot that have the axles further forward.

 

[DavidNJ]

They are not common, but they seem to exist:

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