Newbee needs help - How High should my towball be off the gro...

[Lutz]

Ray, the maximum allowable height of a towball when the car is fully laden is 420mm and the minimum height of the coupling when the caravan is standing level is 395mm. This automatically results in a potential slightly nose up attitude, which would be even greater if the car is not fully laden but at kerbweight.

Referring to your excerpt out of the the AlKo manual Page 2: However a nose up ="high skid risk together with poor braking" Load too far back.

Nose down="Steering and braking ability reduced, increased loading on the rear axle and chassis of the tow vehicle"Load too far forward.. That's exactly the point that I was trying to get over. It suggests that the nose up attitude is due to the load being too far back. This may be the case, but need not necessarily be so.

We've got to give both car and caravan manufacturers tolerances on their dimensions, so expecting the outfit to always stand level is rather utopian.

 

[ProfJohnL]

At the risk of being accused of going back on my word, I feel that I should comment on Ray's last posting in the order it appears.

As far as I can tell from reading the posts, Neither Lutz or I assume that a nose up attitude suggests the nose load is too small, Lutz was giving his opinion that others who see the condition may consider the nose load to be too low and that view may be based on a belief it should be level or nose down.

If a an outfit is presented nose up, then it might raise questions about nose load or hitch height but it would be wrong jump to a conclusion that either the nose load is too low or that the tow ball is set to high. The correct response should be to measure the conditions compare them to the permitted limits and regulations and draw a conclusion from the factual evidence.

I find it hard to believe there is no Visible difference in attitude of Ray's outfit when the nose load is changed between 80 and 100Kg. It may only be a small difference, but by adding load to the hitch the rear suspension of the tug must respond, and unless you have self levelling suspension there would be a measurable change in the height of the tow ball and a corresponding change to the attitude of the caravan or trailer.

Based on the quotation from the Bailey caravan hand book, it is clear that Bailey design that caravan to ride level or nose down. That is their choice. Bailey must be aware of the EU regulations that specify the permitted range for the height of a tow ball, and they will have arranged their design of caravan to tow level or nose down with compliant heights of tow ball. It follows therefore that if their caravan is nose up, then something must be wrong. Obviously one possibility would be the tow ball set too high and by logical extension it would be out of the permitted EU range. It should not be assumed that this line of thought applies to all makes of caravan or trailers. Other manufactures may have different views on attitude.

The Alko manual is only illustrating how extreme poor loading of their chassis may affect an outfit. If these extremes were tried, It would not be possible to archive the recommended nose weights, and so the outfit would be illegal anyway.

With regard to nose loads, I stated that the EU has regulations on nose loads, that is not the same as the EU setting nose loads. Ray is correct that the respective manufactures rate their own products, but the EU regulations tell us that you must not exceed the lowest limit of any of the items involved in the tow hitch assembly.

Finally, I regret that this thread has exposed a difference of opinion and become rather embroiled in what are academic differences.

The essential answer to the original question is ; the centre of the tow ball must be between 350mm and 420mm from the ground with the loaded caravan attached.