Off Road Trailer Axle and Suspension Guide


In North America, the history of travel trailers can be traced back to the early 1920s. In those days, trailers became known as Caravans with very few creature comforts. As trailers became more livable in the 1930s and 1940s, they earned the name ‘house trailer’.

Pop-up / tent trailers have been around since the early 1900s. As more people began to travel in their newly owned automobiles, the tow-behind trailer became a popular necessity. Manufacturing of tent trailers increased during the 1960s and 1970s.

Teardrop trailers first appeared in the 1930s. While some teardrop trailers are not off-road specific, many come with off-road tires and a more rugged construction. All storage and living space are contained inside the trailer while the kitchen is accessible from the outside.

UGOAT trailers – Utility Go-anywhere Off-road Adventure Trailer – are designed as a tough-as-nails option for traveling deep into the backcountry (way off-road!). 

In this article, we’ll answer some questions about the Axle-less trailer suspension system.

Off Road Trailer Axle and Suspension

How does the Axle-Less suspension work?

It all began with the US military. They had a problem. 

Trailers that were used to pick up the injured on the battlefield had limited use. The medics needed a trailer that could go where an off-road vehicle could go.

Turns out it was the straight axle that presented all kinds of limitations. They wanted a suspension that would allow the trailer to navigate smoothly, without incident.

Early designs for this military rescue trailer were the beginnings of a new concept for off-road trailer suspensions. As you will see, this radical departure from a conventional leaf spring suspension has led to a number of benefits for the off-road community.

Let’s take a closer look at how each separate component works together to create the safest and smoothest off-road trailer suspension on the market.

Steel Hanger: The hanger facilitates a simple, bolt-on installation. Each hanger comes with 3 laser-cut holes, a template to mark the frame where holes need to be drilled for mounting. Additionally, the steel hanger has a 2” square hole through which a steel pipe can be fed for frame reinforcement. 

Control Arm: A control arm is a critical component of an independent suspension system, controlling the motion of each separate wheel, allowing the tires to articulate smoothly. Without a control arm, the ride would be rough. The control arm on the Axle-less suspension holds the jounce spring, the rebound spring and the outboard arm in place.

Premium urethane bushings help to fasten the control arm securely to the hanger. The urethane bushing adds to the overall quietness. As a result, you won’t have to listen to any annoying squeaks and rattles when towing your trailer.

Jounce Spring: Aeon® rubber springs are the heart of every Timbren solution. That’s because rubber springs have certain characteristics that you don’t get with metal and air: Progressive spring rate and shock-absorption.

The jounce spring used in the Axle-Less suspension is Timbren’s latest development in rubber spring technology. Its unique wedge-shaped design works perfectly with the up and down motion of the control arm. Made entirely of natural rubber, the jounce spring delivers a perfect combination of strength, stability and smoothness.

Rebound Spring: The rebound spring is a single-convoluted Aeon® hollow rubber spring that plays an important role. This ‘hidden’ spring puts constant tension on the much larger jounce. That way - full or empty – the trailer always maintains a smooth ride. The unique characteristics of a hollow rubber spring apply to the rebound: Progressive spring rate and shock absorption. Both jounce and rebound springs contribute to a quiet, controlled ride even on rough terrain.

Outboard Arm: The last piece of the suspension puzzle is the outboard arm. The outboard arm comes with built-in camber. Metal shims help to make any necessary adjustments. If the spindle gets damaged, replacing it is a snap. Just undo the four bolts, remove the damaged arm and bolt the new component in its place.

Summary: The Axle-Less is basically five components that work together to produce what many agree to be a better off-road trailer suspension. It’s better because it allows for:

  • Maximum ground clearance
  • A smooth, quiet ride
  • Greater control even on the roughest terrain.

Off Road Trailer Axle and Suspension

How to retrofit a trailer with the Axle-Less suspension?

Once you have removed the old leaf spring suspension from the frame, you’ll need to grind the edges of the frame to make them smooth enough to install the Axle-Less.

After these preliminaries, you’re going to need to decide which model number is the correct one to purchase. The Axle-Less suspension comes in various weight ratings, everything from 400 lbs. up to 5200 lbs. Here’s how to determine the correct one for you.

Get an accurate weight of your trailer fully loaded. Then add 20%. For example, if your trailer weighs 2600 lbs., an additional 20% comes to 3120 lbs. (2600 + 20% = 3120)

The next size up from 3120 is 3500. Therefore, the model number you’re going to need is:

If you plan to go off-road or overland camping, you’ll need to choose an HD model. HD models have heavier-gauge steel and a more robust design. Not only that, tire size will also determine which spindle you’re going to need. A regular tire is 235 mm (or 9.25 inches). Anything wider will require a longer spindle. Here are the configurations available for the 3500HD models:

Off Road Trailer Axle and Suspension

Timbren Axle-Less suspension how much does it weigh?

Timbren Axle-Less suspensions come in 9 different weight classifications. Here are the shipping weights for each classification:

All Axle-less products are shipped in boxes, making them courier-ready.

Off Road Trailer Axle and Suspension

How to install the Axle-less suspension?

There is a right way and a wrong way to successfully mount an Axle-Less to your trailer. Here are four important steps to follow when installing an Axle-Less suspension.

  1. Bolt the outboard arm to the control arm with supplied fasteners using appropriate torque values.
  1. Make sure the trailer frame is perfectly square. You can check by measuring from the rear right corner to the front left corner, and from the rear left corner to the front right corner. If both measurements are equal, the frame is square. (Measurements must be within 1/8th of an inch.)
  1. Install hangers to the trailer frame. 
  • Mark frame rails where the centerline of spindles should cross
  • Confirm measurements are equidistant from the front center of the frame
  • Clamp hangers to frame making sure the spindles line up with marks on the frame
  • Using holes in the hanger as a template drill 3 holes into the frame
  • Bolt hangers to frame with appropriate fasteners and torque values
  1. Reinforce frame with either an additional frame bracket bolted to the inside of frame or by sliding a cross-member through both hangers and bolting it using appropriate fasteners.

Off Road Trailer Axle and Suspension

How much weight can Axle-Less handle?

It’s important to note that – as outlined in the section “How to retrofit a trailer with the Axle-Less suspension?” – each weight category can handle a certain amount of weight within certain parameters. The following are the weight categories for Axle-Less:

Use the following parameters when determining which Axle-Less Trailer Suspension is best for you:

Get an accurate weight of your trailer fully loaded. Then add 20%. For example, if your trailer weighs 2600 lbs., an additional 20% comes to 3120 lbs. (2600 + 20% = 3120)

The next size up from 3120 is 3500. Therefore, the model number you’re going to need is ASR3500S05. If you require a drop spindle arm or a lift spindle arm, choose one of the following:

Off Road Trailer Axle and Suspension


If you read through the above Q & A, hopefully, you have a clearer understanding of the Axle-Less trailer suspension system. Click here for more info on how to purchase the Axle-Less suspension.

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