Finding the Right Size Coil Spring for Your 4x4

Upgrading or replacing the suspension on your 4x4 is one of the most important decisions you can make for vehicle performance, safety, and comfort. Whether you use your vehicle for touring, towing, off-road adventures, or daily driving, choosing the correct coil springs is essential for maintaining ride height, load carrying capacity, handling, and suspension articulation. 

What Are Coil Springs?

Coil springs are a key component of your 4x4 suspension system. They are heavy-duty steel springs designed to absorb impacts from rough terrain, support vehicle weight, and maintain proper ride height.

In most modern 4WD vehicles, coil springs are fitted alongside shock absorbers to provide both flexibility and control. While the shock absorber controls movement and dampens bouncing, the coil spring supports the vehicle’s weight and absorbs suspension compression.

The Main Functions of Coil Springs

• Support vehicle weight
• Maintain ride height
• Improve ride comfort
• Allow wheel articulation off-road
• Help maintain tyre contact with the ground
• Assist with load carrying and towing stability

Different coil springs are designed for different applications. A touring vehicle carrying constant accessories such as bull bars, winches, roof racks, drawers, or long-range fuel tanks will require a different spring rate than a lightly equipped weekend 4WD.

Why Choosing the Correct Coil Spring Matters

Selecting the wrong coil spring can negatively affect both performance and safety. Choosing the ideal coil spring balances ride comfort with load support and intended vehicle use.

Springs That Are Too Soft

If the spring rate is too soft for your setup, you may experience:

• Excessive body roll
• Suspension sagging
• Bottoming out
• Poor towing performance
• Reduced ground clearance
• Premature suspension wear

Springs That Are Too Heavy

Overly stiff springs can also create problems, including:

• Harsh ride quality
• Reduced suspension flex
• Poor traction off-road
• Increased stress on suspension components

West Coast Suspensions Coil Spring Sizes

How to Measure Coil Springs

Correctly measuring a coil spring helps ensure proper replacement or upgrade selection. Below are some of the most commonly referred to measurements when it comes to coil springs.

Free Height

This is the total height of the spring when it is not under load. Measure from the top coil to the bottom coil while the spring is removed from the vehicle.

Outside Diameter

Measure across the widest point of the spring. This helps determine compatibility with spring seats and suspension mounts.

Wire Diameter

Measure the thickness of the steel coil itself using vernier calipers or a micrometer. Thicker wire generally indicates a heavier spring rate.

Number of Coils

Count the active coils in the spring. This affects spring compression and ride characteristics.

Installed Height

Installed height is measured when the spring is fitted and carrying the vehicle’s weight. This measurement helps determine sag and spring performance over time.

Coil Spring Maintenance

Like all suspension components, coil springs require regular inspection and maintenance. Although coil springs are extremely durable, harsh off-road use, overloading, corrosion, and age can eventually reduce performance. Below are some key maintenance tips to keep them in top shape:

Regular Visual Inspections - Look for Uneven ride height, Bent or damaged coils, Coil contact marks.

Clean After Off-Road Driving - Mud, salt, and debris can trap moisture and accelerate corrosion. Washing the underbody after beach driving or muddy tracks helps extend spring life.

Check Suspension Alignment - Incorrect wheel alignment or worn suspension bushes can place additional stress on springs.

Avoid Constant Overloading - Repeatedly carrying loads beyond the spring’s designed capacity causes premature sagging and fatigue.

Inspect Shock Absorbers - Worn shocks can increase stress on springs by allowing uncontrolled suspension movement.

How Often Should Coil Springs Be Replaced?

There is no fixed replacement interval for coil springs because lifespan depends heavily on usage and conditions. However, many 4x4 coil springs begin showing wear between:

• 80,000km and 150,000km for heavily used vehicles
• Longer for lightly used touring or daily-driven vehicles

Choosing the right coil spring for your 4x4 is about more than simply lifting the vehicle. The correct spring setup improves comfort, handling, load carrying ability, and off-road performance while protecting other suspension components from unnecessary wear. If you need help find the right components for your vehicle, get in touch with our friendly team of 4x4 suspension experts.