Double axle caravans

Or even

If you can't blind them with science baffle them with bull

It would be pure coincidence if the caravan were standing level when ready to be hitched up to the car and even more so when it is actually attached. Differences in loading conditions in the car and the caravan result in different standing heights and consequently different attitudes of both car and caravan. There is no reason why both should be level. Production tolerances in the suspension units also have an effect so that even when standing on its own and level, the axle loads of a twin axle caravan are unlikely to be the same.

It would also be pure coincidence if the noseweight were at the level required after initial loading of the caravan without some need to jiggle around with the load to get it right.

For that reason the axle loads on a twin axle will never be the same.

My Bailey T/A has a 90kg nose weight ex factory before any load is applied. The OP seems to think that because it is a t/a the nose weight is zero before loading - which is not the case.

Yes, that was the impression that I got, too.

The other thing to point out is to be aware that dips and humps in the road cause the nose of the a frame to pitch up and down as the pair of axles follow the topography. This can be quite uncomfortable on some roads, especially if your caravan wheels are following, or weaving , following longitudinal dips in the road caused by Lorry traffic.

Srgds

My pal who has a TA Sterling asked to borrow my Milenco noseweight gauge. When his van was loaded as he normally did. The Gauge showed 150kg, much to his amazement!!!!

Some judicious adjustment of materials about the TAs and we managed to get an acceptable 80kg on the nose. He is away atm so will check on performance on his return!

Imo  there has to be a sensible nose-weight or the tail will wag the dog. To have the nose-weight as a negative would be tending to disconnect the outfit - not a good idea.

Is it Bull? (wrong) If you think so it would be more useful to say why you disagree.

May be too wordy for some but I thought it was an interesting discussion on the axle load distribution of twin axle caravans and the assertion made that the rear axle would be carrying more load when towing.

Level caravan (however unlikely) = equal axle load, Nose down attitude very likely/desirable when towing = more load on Front axle than the rear.

Level caravan doesn't necessarily mean that the axle load is equal. It all depends on how the suspension is set up and on the spring rate production tolerances.

Also, why should a nose down attitude be any more desirable than a level one, or even a slightly nose up one? Standing height tolerances of both car and caravan can, under adverse conditions, result in a slight nose up condition even though all dimensions are within those specified in the regulations.

Stephen P You are absolutely correct in your assumptions - a twin axle is no different from a single when it comes to nose weight. You must always have nose weight bias regardless of what axle configuration you have. The axles will adjust to marginal height differences. When you load the van check the the nose with a scale try to get it tto near the maximum the tow bar allows. On a caravan with an AlKO chassis the suspension is not compensated between the two axles therefore the front will invariably always have more weight on it since it starts to compress before the rear and the rear loses some of the load ( you can easily check this by using a weight bar to see how much difference there is. Axles with a compensated system will ensure that the load is equal and this does mean tyre wear and braking is better balanced. Alas this does not apply to the former. There is a small advantage though in that your mover will work much better when turning since the rear axle will not resist as much. Don't be misled by height adjustments on the nose - if it is too high then you are simply lifting the front axles off the load but you still have your positive load on the nose - you must still ensure it is not over the limit and don't forget you are trying to lift the weight of the front axle unsprung weight, it is better to have a slightly down position on the nose ie low on the height , the reason for this is that any pitch will always push downwards on the tow car, however, braking torque will tend to push down on the nose so not a serious problem.

When I first started towing our twin axle, I loaded it to achieve a 120kg noseweight which is within limits of the Winterhoff hitch and the limit of the car (150kg on a Range Rover Sport)

The car has air suspension so after connecting the caravan and starting the car, the rear would rise to the level predetermined by the level sensors which is the same as if the car is solo.

However, due to the height of the fixed towbar, despite the noseweight and the air suspension, the attitude of the caravan was slightly nose down and you could visibly see the tyre deflection and position of the front axle wheels versus the rear axle wheels, that the front caravan wheels were carrying a greater load.

Towing like this was ok but there was quite a bit of pitching over bumps in the road.

I purchased a GAP diagnostics IID tool which allows changes to the suspension heights which can be saved as presets. Hooked up the caravan with the same 120kg noseweight and then using my phone, connected to the IID tool via Bluetooth, adjusted the rear height of the car so that the caravan was level. Now the wheels on the caravan looked to have equal tyre and suspension deflection. Driving the combination was so much better, a lot less pitching and it felt much more stable.

Now every time I tow, it’s just a case of plugging the tool into the car and selecting the preset I saved on my phone. All that changes effectively, is the towball height to give a level riding caravan.

I have no idea why this set up tows so much better, I can’t for one moment explain the physics behind it. The noseweight hasn’t changed, just by raising the rear of the car lifts the towball height to achieve a level caravan, and bingo, the towing experience is drastically improved.

Can anyone explain?