What are typical symptoms of a worn coupling bolt and what can I do?

As trailer couplings can differ in their design, especially from different manufacturers, it is essential to refer to the relevant product documentation from the respective manufacturer. 

The following examples follow Ringfeder's recommended guidelines to support optimal compatibility and reliable performance. 

What are the typical symptoms of a worn coupling bolt, and what could be causing them? 

1. The coupling bolt moves up and down slightly when the traction vehicle pushes and pulls at the drawbar. 
2. The coupling bolt’s wear or eye marks are incorrectly positioned (not centred on the designated wear surface) due to a worn wear plate and/or incorrect drawbar height.
3. The coupling bolt’s wear/marks from the eye are below and above the coupling bolt’s biggest diameter. This is caused from a drawbar that is connected at the wrong height
4. Quick wear, which leads to play between the vehicle and trailer; constant jolting between the vehicle and trailer may occur.

What signs can be observed? 

1. Observe any vertical movement of the coupling bolt when the vehicle pushes and pulls at the braked trailer. 
2. Check the coupling bolt’s wear pattern. 

Picture 1, green field in the middle displays the correct wear amount. 

Picture 2, red field indicates a drawbar eye that is too low due to a worn wear plate 

Picture 3 shows a drawbar that is connected at the wrong height relative to the coupling, i.e. wear both above and below the coupling bolt’s green field. 

How can I find out whether the wear limit has already been reached? 

There must be no vertical movement of the coupling bolt when the vehicle is pulling or pushing the braked trailer. There should be no wear outside the minimum diameters, specified by the manufacturer of the coupling. Below you’ll find an example for Ringfeder 40mm and 50mm couplings. 

It is not always possible to notice a worn coupling bolt from the drivers cabin. When driving in combination with a central axle trailer and a rigid drawbar a worn coupling bolt can sometimes be felt in the cabin but with a hinged drawbar it is highly improbable.  

Therefore, a regular check of the coupling bolt by measuring is highly recommended. 

What should I do if the above applies? 

• If the wear on the bolt is too low or the wear plate’s minimum height is indicated, it must be replaced. When the wear to the eye for the bolt is too great, the drawbar’s balancing force will be reduced; the eye must rest firmly in the coupling mouth. 
• If the wear looks like it does on coupling bolt no. 3, the drawbar is at the incorrect height relative to the coupling, in which case its attachments should be rebuilt; the drawbar should be horizontal in the operating position. 
• If the bolt is outside of the specified limits in terms of the smallest diameter, the  coupling bolt must be replaced. 

What should I do if the above does not apply? 

If you cannot recognise the causes described above, we recommend that you take a look at the inspection guidelines, which can be found for Ringfeder here Support | Ringfeder. 

Both the operating and assembly instructions may contain helpful information, which you can find for Ringfeder on the website, in the online product catalogue for the corresponding coupling. 

In case of doubt, however, it is always advisable to visit a qualified workshop.