08 Feb 2022

How Do Braked Trailers Work

If you’re thinking about buying a trailer, the chances are that you have come across over-run brake systems. Over-run braking systems are fitted on all caravans and trailers that are above the 750Kg weight capacity. It’s important that you understand what over-run brake systems are so that you can choose a trailer appropriately. 


If you’re looking to buy a half-pipe or scrap trailer, get in touch with Colson Trailers today. 


Without further ado, let’s get into ‘how do braked trailers work? 

What are braked trailers? 

It would be considered unsafe if there wasn’t a way to apply brakes to your wheeled attachment while driving, particularly when driving downhill for example. On a lorry trailer, brakes are activated through a compressed air system. Unfortunately, this method cannot be used on cars, which is why a new way of breaking was invented. 


Often known as ‘over-run’ braking systems, a braked trailer has brakes fitted that will be applied through a mechanical linkage that is connected to the tow bar. This system is great as when the car brakes, a force is applied to the tow bar which in turn activates the linkage to apply to the trailers brakes.

How do braked trailers work? – The full explanation

The braking system works, starting with the tow ball which exerts a mechanical force between the towing vehicle and drawbar. If the trailer is being pulled forward, the force will be in the direction opposite to travel. The system works when you break, by being activated when the trailer tries to continue at the same speed, travelling forward in comparison to the towing vehicle. By doing so, the drawbar and spring are compressed. When the compression is activated it forces the lever to rotate which then will pull on the brake rod, activating the brakes.


As you may assume, the harder you apply the brakes, the more braking effort is applied. The opposite effect happens when you speed up, as the force being transferred eases, so does the braking effort.

What should we look out for?

To a certain extent, this system is self-regulating, although there are some problems to this mechanism and keeping yourself informed on this can help you stay safe when towing a trailer. 


The system that we talked about before is only self-reliant due to a sprung damper system. If the mechanism was an un-dampened spring, the braking system would not be effective at all. If this was the case, as you brake, the trailer would slow faster than the towing vehicle, releasing the brakes which would, in turn, cause the towing vehicle and trailer to keep bumping into each other. 


Don’t worry, the systems are advanced and will not crash into one another every time you decide to tow your trailer. To stop this from occurring, a damper or shock absorber is used to reduce the bouncing of the spring. For this to be effective, the spring and damper rates must be correct in regards to the caravan rate. 

What should we expect for the future of braked trailers?

In the future, it is expected that towing vehicles will become lighter, while trailers will become heavier. Due to this, it’s obvious that towing to the limit of any tow vehicle will be more likely. We are starting to see the future in Australia, New Zealand, America and Canada, where power assisted systems for trailers above certain weights are required. You can get power-assisted systems relatively easily today, with many different options available. There are also many companies that specialize in electronic braking systems. 

Thank you for reading our blog ‘How do braked trailers work?’. If you’re looking for half pipe trailers or scrap trailers for sale, take a look at Colson Trailers today.