What’s under your trailer? We take a look at the working parts of the axle

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We all know that the axle is one of the most important components of any trailer, but what is it exactly, apart from a shaft that connects the wheels to the chassis.

The trailer parts or running gear – the axles, brakes and suspension – are a crucial component of your touring experience and need regular maintenance and checks, so it is important to become familiar with them.

Let’s crawl under your trailer now and take a look at its axle.

The basic axle is a round or square shaft (it’s most likely round on light caravans and trailers). It is usually fixed to its surrounds with the wheels rotating around it.

Beam axles come in different styles. The ‘straight’ beam is the simplest and most common, used mainly for domestic and boat trailers.

The ‘overlay’ beam axle, on the other hand, has stub axles welded on top of the main structural beam. This has the effect of lowering the trailer height, allowing greater stability and lower wind resistance.


Trailers over a certain weight are required by law to have brakes. If your axle is braked, you will be able to see the brakes on the inner side of the hub face, usually connected by means of a brake flange.


Very basic axles have no added suspension capabilities, but it is most likely your trailer or caravan will have either leaf spring or rubber torsion suspension.

Leaf springs such as the Rocker Roller spring leaf suspension system will be attached with U bolts to the axle, adjacent to the wheel hub. The placing is important – not so close to the wheel hub that they rub against the tyre, but also not so far away that they become a leverage problem, possibly causing the axle to bend.

Some axles have built-in suspension capabilities, such as the Independent Rubber Suspension axle, which is a hexagonal axle tube housing rubber elements held in place by an inner tube. Suspension movement between bump and rebound compresses the rubber elements thus providing dampening of road shocks.

So, it seems ‘axles ain’t axles’. While they all perform the backbone function of connecting the wheels to the trailer, many also provide the neural pathways for braking and suspension capability, making the world of difference to your towing experience.

Is it time to upgrade the brakes on your trailer? Electric brakes might be the answer.


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