Get on Top of Towball Heights

FAQ – Get on Top of Towball Heights with CBS AUTOMOTIVE Cambridge

How do you measure towball height?

We at CBS AUTOMOTIVE Cambridge towball height is measured as the vertical distance between the ground and the centre of the towball. This must be measured on flat and level ground also, the laden condition of the vehicle must be known. (Note; In the case of “coupling height”, this is the position of the centre of the towball location when within the coupling head).

What height should the towball be?

CBS AUTOMOTIVE Cambridge follow The EC Directive 94/20/EC states that the towball height should be between 350 and 420mm with the vehicle in the ‘laden’ condition. Laden condition may have been defined (by the manufacturer) as either fully laden (the maximum technically permitted mass of the vehicle as shown in the vehicle handbook), or, conventionally laden (defined as 68.5kg per specified passenger seat and 6.5kg of luggage per specified passenger and located in the centre of the luggage storage area). Alternatively, the towball may be at the height or height range specified by the vehicle manufacturer in the homologation documents and possibly the vehicle handbook. Our tow bar specialists are always on had to help should you have any further questions.

What height should the trailer/caravan coupling head be?

The EC Directive states that this should be 385 to 455mm with the trailer in the ‘laden’ condition. ‘Laden condition’ in this instance is when the trailer is loaded to its maximum specified mass, with this evenly distributed over the loading area.

Should my caravan (or trailer) be level?

Not necessarily! Many think (incorrectly) that it is essential to have the trailer chassis perfectly level and go to great lengths to try and achieve this. However, from the previous two questions it can be seen that there is inherently a wide height range for both the towballs and the trailer couplings. Also, the specifications are written to promote a tendency towards a slightly ‘nose down’ attitude of the trailer, with the medium of the range for the trailer being 35mm higher than the medium of the height range of the towball on the towing vehicle. Furthermore from the permissible ranges and laden definitions it can be seen that the difference can be extreme

e.g. –   Towball at 350mm (fully laden vehicle) and trailer coupling at 520mm (not untypical of an unladen trailer)……a difference of 170mm! –

Towball at 510mm (unladen long suspension travel vehicle) and 385mm trailer coupling height (for fully laden trailer)…..a difference of 125mm!

The situation is further complicated by the fact that the towbar/towball is controlled by an EC directive, whilst it is currently not mandatory for the trailer to be EC approved – and very few are. We at CBS AUTOMOTIVE Cambridge only fit tow bars which carry full approval.

My towball is too low. What can I do?

Maybe the towball is in the correct height range and the trailer coupling height is incorrect. For some reason, this is automatically assumed to be the ‘fault’ of the vehicle/towbar – measure and check!

Unless there is a grounding or stability problem there is no technical reason to do anything. However if it is necessary, then in the case of an EC type approved towbar the options are:

Use a different towball location (some vehicles have two or more different towball fixing heights).

Check with CBS AUTOMOTIVE Cambridge that the towbar has been installed correctly and whether there is any scope to loosen and retighten any components to raise the height – on some towbars this can regain up to 40mm in height!

Check the vehicle suspension. This can wear and settle over time. Are spring assisters or suspension changes or adjustments possible? – Modifying the trailer coupling height should be considered. – If the issue is the jockey wheel grounding, can this be repositioned? – Does the vehicle have sports’ suspension, often 15-50mm lower than standard models? Check against the chassis number with the dealer or just call us and we can check for you.

My towball is too high. What can I do?

As in the previous question, it may just be the trailer/caravan that is non-compliant – measure and check! Similarly, in the case of EC type approved towbars there are limits as to what can be changed. Options include:

Use a different towball location (some vehicles have two or more different towball fixing heights).

Possibly use a drop plate (some towbars are tested and EC type approved for use with drop plates – check the towbar installation instructions).

Alternatively, if it is a commercial vehicle it is currently not mandatory to have an EC compliant towbar and it may be possible to use a drop plate (always check with the towbar manufacturer).

Can I use a ‘raiser plate’ to increase the towball height?

No! To do so could significantly increase the leverage on the towbar/towball interface, and could result in damage or failure of one of the towing system components.

It would also almost certainly invalidate the EC approval of the towbar. There are very few instances where a raiser plate can be used. Also these must be with written permission of the towbar manufacturer and use is usually limited to special applications where a pin and jaw (not towball), is raised to the same position as the towball.

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