Coilover Spring Selection & Setup

Coilover suspension is often seen as a dark art; the realm of hardcore off-roaders and race teams. In reality, it’s a highly tunable, flexible system that can completely transform the handling, comfort and capability of your 4WD. If you’ve decided that OE suspension just won’t cut it, this guide will help you understand the fundamentals of coilovers, spring rates, and tuning principles so you can set your rig up correctly from day one.

Why Coilovers?

The biggest advantage of coilover shocks is adjustability. Unlike fixed-rate OE struts, coilovers are fully serviceable and tunable. With machined component design.

They allow you to:

• Swap springs in a wide variety of rates and lengths.
• Dial in preload to achieve your desired ride height.
• Fine-tune suspension behaviour for different terrain or loads.

Springs are available in multiple free lengths (typically 10–18 inches) and spring rates ranging from 80 lb./in right through to 800 lb./in. Superior Engineering carries a wide range to suit most 2.0 and 2.5 inch body coilovers, giving you the flexibility to build a suspension package tailored to your driving style and vehicle weight.

Dual-Rate Coilovers Explained

For off-road applications, dual-rate setups are most common.

These use two coils stacked on one shock:

• Tender spring (top coil): Softer, provides comfort and compliance over smaller bumps.
• Main spring (bottom coil): Stiffer, progressively takes over during heavy compression or larger impacts.

The combined rate of both springs determines how the suspension behaves in the first portion of travel, before the tender coil compresses fully and hands over to the main spring.

Refering to the Spring Rate Formula
Example: A 150 lb./in top coil stacked with a 250 lb./in main coil equals a 93.75 lb./in initial rate. Once the tender coil compresses fully, the shock runs on the main 250 lb./in coil alone.

Step-Up Rate (SUR) and Shock Tuning

The difference between the two coil rates is known as the Step-Up Rate (SUR). It controls how aggressively the suspension firms up as it transitions from dual-rate to single-rate operation.

Slower vehicles: 100–200% SUR.
Faster rigs: 200–300% SUR.

The transition point is set using the threaded dual-rate nuts on the shock body. Adjusting these rings changes when the slider engages, giving you control over when the tender spring stops contributing.

Coil Length and Travel

Coil length should match shock travel wherever possible. For example, a 14-inch travel coilover should ideally run two 14-inch coils. If mounting hardware permits, running a slightly longer bottom spring can improve slider position and reduce the risk of the spring unseating at full droop.

How to Select Spring Rates

The starting point is knowing the sprung weight on each end of your vehicle. With that, plus details like shock travel, mounting angle and desired ride height, you can calculate a target spring rate.

See the below example:

• Sprung weight front: 1000 kg.
• Shock travel: 14 in (with 6 in shaft showing + 1 in preload).
• Mounting angle: 80°.

Calculation gives an initial rate of ~124 lb/in. This could be achieved with a 200 lb/in tender spring and 350 lb/in main coil.

Ride Balance and Pitch Control

Front-to-rear spring rates affect more than just height, they also control pitching (the bobbing motion of the vehicle). Incorrect balance can ruin traction and stability.

• Slow flexy crawlers: softer, more droop-biased setup.
• All-purpose off-road rigs: balanced rates, moderate preload.
• High-speed off-road / highway use: firmer rates, higher suspension frequency to control body movement.

A good rule of thumb is to run the rear frequency 10–20% higher than the front for stable handling.

Preload and Setup Tips

• Start with ½–4 inches of preload to keep coils seated and maintain correct droop.
• Lower preload improves handling and reduces sag under load, but can reduce down-travel force.
• Higher preload helps push wheels down into bumps but may stiffen ride unnecessarily.

Conclusion

Coilovers aren’t guesswork, they’re a tunable system that, when set up correctly, can deliver unbeatable ride quality, off-road performance and vehicle control. By understanding spring rates, step-up rates, coil lengths and preload, you’ll take the “mystery” out of coilovers and set your rig up like the experts do.

Superior Engineering stocks a wide range of 2.0 and 2.5 inch remote reservoir coilovers, premium coil springs, and all the hardware required to build your ideal suspension system. Whether you’re chasing flex for crawling, balance for touring, or control for high-speed desert running, we’ve got the knowledge and components to help you get it right the first time.