The Anatomy of Healthy Cars: A Service and Repair Blog
A Spring In Your Step: Should You Have Your Trailer's Leaf Springs Replaced With Torsion Springs?
by Brittany Marshall
The suspension system is one of the most important parts of any load-bearing trailer, providing cushioning against bumps and dips in the road to provide a smooth towing experience and protect whatever cargo your trailer is carrying. However, you have a couple of options when it comes to the kind of suspension system your trailer uses, and traditional reliable leaf springs are giving way to more compact torsion springs for many trailer applications.
However, while leaf-sprung axles are an old and venerable technology, they still have several advantages over modern torsion springs—conversely, torsion springs excel in some aspects but also have disadvantages compared to leaf springs. As such, if you are considering replacing your trailer's leaf springs with torsion springs you should take stock of the pros and cons of their use before you buy and install them.
What are the advantages of keeping your trailer's leaf springs?
Simplicity: Leaf-sprung axles are simple mechanisms, with the entire axle held up on robust metal springs. This simplicity allows leaf springs to be inspected and maintained easily, and minimises the amount of moving parts that may need to be replaced over the service life of your trailer. Damaged or worn components can be repaired or replaced relatively easily.
Increased turn stability: Keeping the entire axle suspended gives increased stability over individual springs, allowing for less rocking and leaning around corners and making loading (especially if you're carrying heavy loads) easier and safer.
Decreased ride height: Because the springs are constantly compressed by the weight of the axle, a leaf-sprung trailer will sit lower than a torsion-sprung one. This further increases stability and decreases your overall ride height, very useful if carrying tall or unusually shaped loads.
Even tyre wear: Distributing the trailer's suspension across the whole axle also allows tyres to wear more evenly on both sides, preventing unexpected blowouts. This is a particular boon on multi-axle trailers that routinely carry heavy loads.
What about the disadvantages?
Constant maintenance required: Unlike torsion springs, leaf springs are not self-enclosed, and require frequently maintenance (particularly lubrication) to stay in top working condition.
Corrosion: Because of their open construction leaf springs are also open to the elements, and prolonged exposure to moisture (particularly in coastal areas) can promote damaging corrosion.
What are the advantages of replacing leaf springs with torsion springs?
Zero maintenance: Torsion springs do not require lubrication, and their enclosed construction protects them from most external sources of damage. Most are also supplied with galvanized coatings to protect them from rust, so you can run torsion springs for a long time with little oversight.
Smoother ride: Because torsion springs are fitted over the trailer's axle(s) and work individually, they are much better at responding to bumps and grooves in the road, leading to a smoother and quieter ride.
Uneven load bearing: Individual suspension for each trailer wheel also allows torsion springs to cope far better with uneven loads, and can cope far better with the stresses of sharp corners and bends.
Adjustable ride height: While torsion springs will cause your trailer's load to sit higher than it would on a leaf-sprung trailer, this ride height is adjustable, letting you adapt to low bridges and other obstacles on the road.
And the disadvantages of replacing them?
More expensive: Torsion springs are more expensive and difficult to fit than leaf springs, especially if you are seeking to convert a leaf-sprung trailer to a torsion sprung one.
Difficult repairs: While torsion springs are highly durable and reliable, they are very difficult to repair if damaged and generally have to be replaced instead; this can be a complicated and expensive task, and should only be undertaken by professionals in most circumstances.