When upgrading your 4x4 suspension, one of the most common questions we get is: What spring weight do I actually need? With so many different constant load spring options available, it can feel a little overwhelming trying to work out which setup will best suit your vehicle.
Choosing the right spring weight is important because it directly affects your ride height, comfort, handling, and overall load-carrying performance. Whether you use your 4x4 for touring, towing, work, or weekend adventures, selecting the correct spring setup ensures your suspension performs the way it should.
In this guide, we’ll cover some of the basics when it comes to determining the best constant load spring size for your vehicle and setup.
What Does Constant Load Mean?
Constant load refers to the amount of weight a spring is designed to carry while still maintaining the intended lift height, with most 4x4 lifts typically around a 2-inch lift.
For example, if your vehicle has a 500kg constant load rear leaf spring, that means the spring is designed to maintain a 2-inch lift while carrying approximately 500kg of weight in the rear. This constant weight could include things like:
- Canopies
- Drawer systems
- Fridges
- Toolboxes
- Roof racks (where applicable)
- Rear bars with spare wheel carriers
- Long-range fuel tanks
- Towing ball weight
The key word here is constant, this refers to weight that is regularly on the vehicle, not just occasional loads for a weekend trip.
Common Constant Load Spring Options
Most suspension manufacturers offer several constant load spring weight options depending on how your 4x4 is set up. Typical rear spring loads include:
Light Constant Load (Around 100kg)
Ideal for vehicles with minimal accessories and only light added weight, such as:
- Basic tub setup
- Small toolbox
- Light touring gear
These are a common choice for daily drivers that only occasionally carry extra gear or weight in their setup.
Medium Constant Load (Around 300kg)
One of the most common spring options, perfect for vehicles with moderate permanent weight such as:
- Canopy
- Fridge
- Drawer systems
- Rear bar
This setup suits many touring vehicles and dual-cab utes.
Heavy Constant Load (500kg to 600kg+)
These heavy constant load springs are designed for serious load-carrying applications, including:
- Full touring builds
- Service bodies
- Heavy canopies
- Work vehicles
- Constant towing with significant ball weight
These heavier-duty springs are ideal when your vehicle is permanently carrying substantial weight.
How to Determine the Right Spring Weight
The best way to choose the correct spring weight is to work out exactly what is permanently fitted to your vehicle and what load it regularly carries. Ask yourself: What’s in the Back of Your Vehicle?
The easiest way to start is by listing the weights of all of the permanent accessories such as:
- Steel canopy or alloy canopy
- Drawer system
- Fridge and fridge slide
- Toolboxes
- Rear bar
- Recovery gear
- Long-range fuel tank
- Camping gear stored full-time
Even smaller items can add up quickly.
Are You Towing?
If you tow a caravan, camper trailer, or work trailer regularly, ball weight becomes a major factor on how big of constant load your springs need to handle, Tow ball weights can commonly range from:
- 150kg
- 250kg
- 350kg+
This weight sits directly on the rear suspension and should absolutely be considered when selecting your spring rate. If you tow often, especially with heavier ball weights, a heavier constant load spring may be the better option.
Don’t Over-Spring Your Vehicle
A common mistake is choosing springs that are too heavy “just in case.” If your springs are rated for more weight than you actually carry, your vehicle may sit too high and ride harshly, especially when unloaded.
The goal is to match your spring rate to your real-world everyday setup, not your once-a-year holiday trip. Getting this balance right gives you:
- Better ride comfort
- Improved handling
- Correct ride height
- Better towing stability
- Longer suspension life
Need Help Choosing the Right Setup?
If you’re looking at upgrading your 4x4’s suspension and need help determining the right setup for your vehicle, it’s always best to speak with suspension specialists who understand real-world applications. Make sure to get in touch with our team of suspension experts, and we can help you choose the ideal spring weight and suspension package for your build, whether it’s for touring, towing, work, or everyday driving.