What's the Difference Between Slipper and Eye-Eye Leaf Springs?

When building or maintaining a trailer, one of the most important components to get right is your suspension setup. The type of leaf spring you choose can significantly affect ride quality, handling, and long-term durability.

Two of the most common types found on trailers in New Zealand are slipper springs and eye-eye springs. Each has its own advantages depending on your load, terrain, and trailer setup.

Let’s break down the key differences so you can choose the right spring set for your trailer.

What are slipper springs?

Slipper springs are a simple and rugged suspension option. They have a round eye on one end that mounts to a fixed hanger, and a flat, open tail on the other that "slips" into a rear hanger or bracket. This allows the spring to flex and slide as the trailer moves, without the need for extra shackles or pivoting arms.

Common features of slipper springs:

  • Fewer moving parts = lower maintenance

  • Cost-effective solution for most single and tandem axle trailers

  • Simple installation

  • Ideal for farm trailers, boat trailers, utility trailers, and trade rigs

Slipper springs are especially popular for light commercial and agricultural trailers thanks to their durability and minimal upkeep.

What are eye-eye springs?

As the name suggests, eye-eye springs have a circular eyelet at both ends. One end mounts to a fixed hanger while the other connects to a shackle plate or rocker arm, which allows for greater articulation as the trailer rides over uneven surfaces.

Benefits of eye-eye springs:

  • Improved ride comfort on bumpy terrain

  • Better load equalisation in tandem axle setups

  • More articulation, ideal for long-haul or off-road use

Eye-eye springs are commonly found on tandem axle trailers that transport heavy or fragile loads - especially when smooth handling is a priority.

Feature Slipper Springs Eye-Eye Springs
Mounting Eye at one end + open tail Eye at both ends
Parts required Minimal hardware Includes shackles and rocker arms
Ride quality Firmer, more basic Smoother with more articulation
Maintenance Lower maintenance More parts to maintain
Best for Farm, utility, and light commercial trailers Heavy-duty or tandem axle trailers

Which is right for your trailer?

Choosing the right spring depends on how you use your trailer.

Go for slipper springs if you:

  • Want low-maintenance simplicity

  • Use your trailer on farms, worksites, or short hauls

  • Have a lighter single or tandem axle trailer

  • Want to keep build costs down

Choose eye-eye springs if you:

  • Prioritise smoother ride quality

  • Are building a tandem axle trailer with rocker load-sharing

  • Frequently tow heavy loads long distances

  • Expect your trailer to handle rough terrain regularly

Need help selecting a spring set?

Whether you're replacing worn-out leaf springs or building a trailer from scratch, Treadway has the parts and know-how to help.

Check out our full range of trailer spring sets, including:

Still not sure? Give our team a call or flick us a message - we're here to help you get your trailer suspension sorted.