A simple guide to Leaf springs and Torsional suspension
Trailer suspension – a simple guide to leaf springs and torsional suspension
When it comes to suspension, you no doubt want reliability and durability, as well as a product that isn’t going to hit you too hard in the hip pocket. The two most common forms of suspension for trailer axles are leaf spring and torsion. Both have their advantages and disadvantages, which we’ll go into more detail about here.
The default option for all Fabplans products, leaf springs have been around since Roman times – and for good reason. They are more cost effective to manufacture, easy to repair or replace, dependable and more durable than torsion suspension. Leaf springs are made up of high tensile steel plates and depending on the setup, they can carry huge loads while reducing stress on the trailer chassis.
Leaf springs have flat, rolled leaves that are stacked on top of each other in several layers that are then installed below the axle for the suspension system. They are built to an upper load limit and need to be matched to the total trailer and load weight. If the load rating is too low, the springs will quickly fail. If it’s too heavy, the ride will be stiff and harsh, causing structural stress to both the trailer and load. The load on a tandem leaf spring set-up provides a load sharing arrangement between each set of wheels, which means any extra load on each wheel will be partially transferred to the others, maintaining an even weight distribution.
Different capacity leaf springs
Leaf springs need more maintenance than torsion suspension. Some may see this as a disadvantage, but this is often the reason people prefer them. Torsion suspension does not have replaceable or repairable parts so if it ever becomes faulty, you have to replace the entire system.
If you have more than one axle on your trailer, a leaf spring setup is the most reliable option for a steady ride. Leaf springs are also preferable if your trailer is stored on uneven ground, as it will hold up better over the long term because of the independent nature of each spring.
Torsion suspension uses an inner rubber core for its suspension mechanism. It combines the axle and suspension in one assembly, providing an adjustable ride height and a rubberised suspension system. Four rubberised cords are inside the axle housing which handle suspension travel and shock absorption. As each wheel moves up and down, the rubber cords resist the torsional stress, or twisting motion, offering an even wheel suspension system for a smooth ride.
Torsion suspension packages provide an independent suspension solution, which means if there is more weight on one tyre than the other, it can lead to heat build-up and possible blow-outs. Because of this, torsion suspension is preferred for lighter loads and on-highway use. Due to the fact they do not offer weight equalisation, they are not suitable for heavier loads, rough roads or off-highway use.
As mentioned above, torsion axles are not repairable and do not have replaceable parts, which means the whole system needs to be replaced if you ever experience any damage. On the other hand, torsion suspension requires very little regular maintenance – standard wheel bearing maintenance and lubrication is usually all that is needed.