What is a tri-axle?

What is a tri-axle?

A tri-axle vehicle is a heavy-duty truck, tractor, or trailer with three axles grouped together at the rear. Tri-axle vehicles are primarily used to haul heavy loads. The multiple axles and wheels allow for better weight displacement and stability. Dump trucks, tow trucks, and cement mixers usually have a tri-axle design.

The most common tri-axle configuration includes a tandem axle with an air-lifted third axle. In this design, truck drivers can move the lift axle up and down via in-cab controls, so the tires aren’t on the ground if the truck isn’t loaded. Lifting the extra tires in the air when the truck is empty helps save on tire wear and fuel consumption.

When it comes to lift axles, state laws and overall weight capacities may vary, so interstate operators need to understand regulations in their surrounding areas. Some states don’t allow lift axles. They must be kept elevated, significantly lowering how much a driver can carry across state lines.

What is a tri-axle trailers?

Tri-axle configurations are also used for heavy capacity trailers. For instance, because heavy equipment used in construction cannot operate on public roads, high-capacity flatbed trailers must tow them to job sites.

Tri-axle trailers connect to a truck or tractor via a gooseneck hitch or fifth-wheel hitch. Tri-axle trailers sometimes also connect a gooseneck trailer to a fifth-wheel hitch with a kingpin coupler.

What’s the difference between a tri-axle and a quad-axle?

When researching tri-axle commercial vehicles, you may come across quad-axle axles vehicles as well. What’s the difference between these types of vehicles? 

Tri-axle configurations

Tri-axle configurations are smaller and more lightweight. While that may translate to lower tolls and costs, they also have lower maximum operating weights. In trucking, tri-axles are commonly used for local hauling and construction work. For example, a tri-axle dump truck has better maneuverability in smaller spaces than quad-axle dump trucks.

Quad-axle configurations

Quad-axle vehicles usually have two-powered and two-unpowered axles. Quad configurations can support heavier payloads and generally cost more to maintain. Even though they have higher costs, they’re a better choice for longer hauls and interstate transportation. Due to their size, they aren’t recommended for construction sites where maneuverability is tight.

6 key benefits of a tri-axle vehicle

A tri-axle vehicle offers many benefits around its ability to carry more weight safely and efficiently, while also contributing to improved stability, reduced road impact, and enhanced regulatory compliance. Here are a few key benefits fleet managers need to know:

1. Increased load capacity: The primary advantage of a tri-axle is the ability to carry heavier loads. The extra axle and associated wheels distribute the weight of the cargo over a larger surface area. This allows heavy-duty tri-axle vehicles to haul more cargo than their two-axle counterparts, helping to reduce the number of trips needed to transport material.

2. Improved stability and control: The additional axle of a tri-axle vehicle enhances the stability of the vehicle, especially when fully loaded. This increased stability leads to better control, particularly on highways, uneven terrain, and during turns. Furthermore, it can contribute to improved braking performance and reduced risk of tipping.

3. Better weight distribution and reduced road wear: The extra axle of a tri-axle vehicle helps to spread the vehicle's weight more evenly across more tires. This reduces the pressure exerted on each individual axle and the road surface, leading to less wear and tear on roads and bridges.

4. Enhanced traction: With more wheels in contact with the ground, tri-axle vehicles have better traction on the road, especially on loose or slippery surfaces. This can be particularly beneficial in construction, logging, and other industries where vehicles operate in challenging conditions.

5. Improved regulatory Compliance: In various areas across the US, transportation authorities have regulations regarding the maximum weight allowed per axle. Using a tri-axle configuration allows vehicles to comply with these regulations while still carrying substantial loads that might exceed the weight limits for a two-axle vehicle.

6. Optimized fuel efficiency: Some tri-axle vehicles are equipped with a liftable third axle. When the vehicle is empty or lightly loaded, this axle can be raised off the ground. Lifting an axle reduces tire drag and can lead to improved fuel efficiency and reduced tire wear when the extra load capacity is not required.  

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