Why Trailers Extra Wheels Remain Suspended Above The Road and Don't Touch the Ground

If you have ever observed a heavy truck or trailer along the highway, you may have noticed that some wheels do not touch the ground.

At first glance, it may seem as if they serve no purpose. However, transport experts explain that these wheels, known as lift axles, are designed to be used only when necessary.

A lift axle works with a special system that allows the driver to lower it when carrying a heavy load and raise it when the trailer is light.

When lowered, the axle ensures the weight of the goods is distributed across more tyres. This reduces the pressure on each wheel and helps prevent damage to both the tyres and the road surface.

On trucks, these additional tyres are commonly called pusher axles, while on trailers they are referred to as tag axles.

Unlike the main drive wheels, they are not powered by the engine but instead serve as supportive wheels to help balance the load.

Transport regulators in different countries set weight limits depending on the number of axles a truck has.

For example, in some regions of the United States, a truck with three axles can carry up to 55,000 pounds.

But if the truck includes a lift axle, the legal limit rises to about 70,000 pounds. This means that having more axles allows transport companies to move heavier loads while still following the law.

Besides controlling weight, lift axles also save costs in the long term. When not in use, they are raised, which reduces tyre wear and fuel consumption.

If they stayed lowered all the time, they would create extra rolling resistance, forcing the truck to use more fuel.

Despite their advantages, there are some drawbacks. If lowered when the trailer is not carrying a heavy load, they can wear out faster and increase fuel usage unnecessarily.

They can also make it harder for trucks to turn smoothly, since the additional tyres may scrub against the road while cornering.

In Kenya and other countries, trailers with extra wheels are required to undergo inspection by road safety authorities before being allowed on highways. This ensures the lift axle system works properly and complies with load regulations.

Lift axles may appear confusing to the ordinary road user, but they remain an important feature in modern transport.

They strike a balance between carrying heavier goods, protecting roads, and keeping trucks efficient.