21 April 2017
Towball Heights | The position of the tow ball on your car is not a random choice by the the towbar manufacturer, or the towbar fitter. It is pre-determined by the car manufacturer, and by EC Directive Regulation 55. So it is not something that we can change at will to suit your individual caravan or trailer.
How to measure towball height.
Tow ball height is measured as the distance between the ground and the centre of the towball.
It is important to make sure your car is parked on level ground when taking the measurement.
What height should the towball be?
The EC Directive Regulation Number 55 (The standard that all towbars are designed to) states that the tow ball height should be between 350 and 420mm from the ground with the vehicle in a 'laden' state.
The 'laden' state means when the vehicle is loaded with passengers and luggage. The weight used to place the car in its laden state is specified by the car manufacturer in the homologation documents for the vehicle.
This means that when the car is empty of passengers and luggage, the towball can often be much higher than 420mm. In some cases, such as a sport version of a specific model, the towball height will be lower as the vehicle has been lowered. Again, this is deemed by the manufacturer, and you may find more information in your vehicle's user manual. A manufacturer will sometimes state the height of the towball, and this is decided due to the suspension and recommended tyre pressures.
What height should a trailer/caravan coupling be?
The EC Directive states that this should be between 385 and 455mm with the trailer in its laden state. The laden state, in this case, is specified as when the trailer is loaded to its maximum specified mass evenly distributed over the loading area.
Should the trailer or caravan be level while towing?
It is a common misconception that it is essential to have the trailer chassis perfectly level while towing and people often go to great lengths to try and achieve this.
However, from the information above it can be seen that there is inherently a wide height range for both the tow balls and the trailer couplings. So it is not unusual for there to be a height difference between your tow ball and the hitch on your trailer or caravan.
Remember from above, towball heights are 350-420mm, and trailer hitches are between 385-455mm from the ground, so it's perfectly normal for the trailer hitch to be 35mm higher than the tow ball. This gives the trailer/caravan a slightly 'nose down' pitch while towing
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 tow ball on the towing vehicle.
Furthermore, from the permissible ranges and laden definitions, it can be seen that the difference can be extreme.
For example, if your car is fully laden with passengers and luggage, the tow ball could be as low as 350mm. If you try and hitch up to a large unladen trailer then the trailer hitch may be as high as 500mm from the ground.
In other words, the trailer hitch would be 150mm higher than the tow ball on the car, but both the tow ball and the trailer hitch are at perfectly legal and acceptable heights.
My towball is too low. What can I do?
First, measure the height of the tow ball. If it is with the 350 to 420mm range it is correct, and the issue may lie with the trailer or caravan.
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 tow ball location (some vehicles have two or more different tow ball fixing heights).
- 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.
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 both the tow ball and the trailer hitch height to identify where the problem lies. In the case of EC type approved towbars, there are limits as to what can be changed. Options include:
- Use a different tow ball location (some vehicles have two or more different tow ball fixing heights).
- Possibly use a drop plate. (Some towbars are tested and EC type approved for use with drop plates, but not all.).
Can I use a ‘raiser plate’ to increase the towball height?
No, under no circumstances should you raise the height of your towball.
To do so could significantly increase the leverage on the towbar/towball interface. This 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.
It would also almost certainly invalidate the EC approval of the towbar.
