Teardrop Trailer Axles: Leaf Spring vs. Torsion
Teardrop trailer axles are normally divided into two different types: Spring axles ("leaf spring") and torsion axles. While these two types of axles perform the same basic job, the way they go about suspending and cushioning the trailer load is completely different.
Leaf Spring Axles
This type of trailer axle will be immediately recognizable to nearly anybody who has been around motor vehicles for any length of time. Much like the name suggests, spring axles are constructed of stacked flat springs bolted to the trailer frame with the axle then bolted to the springs.
But rather than having the spring over the axle (like on a pickup truck), trailers normally have the axle slung over the springs. This decreases the ride height of the trailer, which is important for many reasons. Load stability is greater on a lower trailer, and they’re easier to load and unload as well.
Spring axles are by far the most popular option when it comes to trailer suspension systems. They’re inexpensive and relatively easy to maintain and can be found almost in stock anywhere in almost any configuration.
Rather than relying on the traditional tensioned and sprung flat steel plates of the spring axle, torsion trailer axles take a different approach entirely.
No metal springs of any type are used; rather, a series of long rubber cords are situated inside a square tube with an inner core piece that the torsion arms are secured to. This type of axle can be difficult to understand just by reading about them. In this case, a (moving) picture really is worth a thousand words:
As you can see, the above video shows the cross section of a torsion axle. The outer square steel tubing is the part that’s actually secured to the frame. The inner square piece is secured to the respective wheels via the torsion bars.
When the wheel moves up and down on bumpy or uneven ground, the inner bar compresses the rubber cords along the length of their bearing surface. The contact points are simply the corners and edges of the center support.
Benefits of the torsion axle include:
- Maintenance free design. Lube your wheel bearings and that’s it!
- No metal-on-metal contact points
- Independent wheel suspension
- Quieter during travel
- Ride height can be easily changed via adjustable torsion bars.
- Cross-bar construction is directly mounted to the frame, and adds stiffness
- Great corrosion resistance, as torsion axles are usually galvanized inside and out
- Warranty typically lasts longer than leaf spring axles