What Are Coilovers?

A coilover is a suspension system that integrates a shock absorber and a coil spring into a single assembly. The name comes from "coil spring over shock." Unlike traditional suspension setups where the spring and damper are separate components mounted at different points, coilovers package everything together, making them compact, easy to install, and highly tunable.

Coilovers are standard equipment in motorsports, from track days and autocross to drifting and rally racing. Their popularity has spread to the street performance community because they allow drivers to adjust ride height, damping characteristics, and spring preload without replacing major suspension parts. For anyone looking to improve handling, lower their car, or dial in a specific driving feel, coilovers are the most direct path to those goals.

How Coilovers Differ from Standard Shocks and Springs

To appreciate coilovers, it helps to understand what they replace. A conventional strut-based suspension uses shock absorbers and coil springs as separate parts. The spring supports the vehicle's weight and absorbs road impacts, while the shock controls spring oscillation. Ride height is determined by the spring's free length and its seat position, which is often fixed.

Coilovers replace both components with a threaded body that allows the spring seat to move up and down. This design gives you direct control over ride height independent of spring preload. Additionally, many coilovers include adjustable damping (compression and rebound), letting you fine-tune how the suspension responds to bumps, cornering forces, and braking. This level of adjustability is simply not available with standard shocks and springs.

Key Components of Coilovers

Shock Absorber (Damper)

The shock absorber is the heart of any coilover system. It controls the rate at which the suspension compresses and extends. Without a damper, a coil spring would bounce uncontrollably after every bump, making the car unstable and unsafe. The shock converts suspension motion into heat through hydraulic resistance, providing the damping force that keeps the tire in contact with the road.

Coil Spring

The coil spring supports the vehicle's static weight and absorbs energy from road irregularities. Springs are rated by their spring rate, measured in pounds per inch (lb/in) or Newtons per millimeter (N/mm). A higher spring rate means a stiffer spring that resists compression more forcefully. The spring rate directly affects ride comfort, cornering grip, and weight transfer characteristics.

Adjustable Spring Seats (Perches)

Threaded spring seats allow you to change the spring's installed height. Moving the seat up or down alters the ride height of that corner of the car. This is the primary mechanism for lowering or raising the vehicle. Some coilovers also allow preload adjustment, which changes the spring's initial compression before the car's weight is applied.

Mounting Hardware and Top Hats

The top mounting point connects the coilover to the vehicle's chassis. Many performance coilovers use pillow ball mounts or camber-adjustable top hats, which allow for alignment adjustments not possible with factory rubber mounts. The lower mount attaches to the steering knuckle or control arm, completing the structural connection.

Understanding Compression

Compression, also called bump damping, occurs when the suspension compresses as the wheel moves upward relative to the chassis. This happens during braking, cornering, and when hitting bumps. Compression damping controls how easily the shock absorber shortens under load.

Compression Damping Explained

Compression damping is created by fluid passing through internal valving in the shock as it compresses. The resistance generated slows the suspension's compression rate. If compression damping is too high, the suspension becomes harsh and resists absorbing road imperfections, leading to a jarring ride and reduced traction on uneven surfaces. If it is too low, the suspension compresses too easily, causing excessive body roll, brake dive, and a floaty feeling.

High-Speed vs Low-Speed Compression

Many modern coilovers offer separate adjustment for high-speed and low-speed compression. Low-speed compression refers to slower suspension movements, such as those caused by body roll in corners or weight transfer during braking. High-speed compression handles rapid movements, like hitting a pothole or a sharp bump. Being able to adjust both independently allows you to fine-tune ride quality without sacrificing cornering support.

For beginners, a good starting point is to set low-speed compression moderately stiff for responsive handling, while keeping high-speed compression softer to absorb sharp impacts. From there, make small adjustments based on how the car feels during your typical driving.

How Compression Affects Handling

Compression settings directly influence transient response. Stiffer compression during corner entry can reduce body roll and improve turn-in response. However, too much compression on the front can cause understeer by preventing the tires from loading properly. On the rear, excessive compression can promote oversteer by reducing rear grip during corner entry. Understanding these dynamics is key to dialing in your setup.

Understanding Rebound

Rebound, also called extension damping, controls how quickly the suspension extends after being compressed. Once a bump has been absorbed, the spring wants to return to its natural length. Rebound damping governs the speed of that return motion. Proper rebound settings ensure the tire maintains contact with the road throughout the suspension cycle.

Rebound Damping Explained

When the suspension compresses, the shock's internal fluid passes through valves that restrict flow. On the rebound stroke, fluid flows in the opposite direction through similar valving. The resistance created during extension is rebound damping. If rebound is too fast, the suspension extends too quickly after a bump, causing the tire to bounce off the road surface. If rebound is too slow, the suspension "packs down" and stays compressed after consecutive bumps, reducing suspension travel and grip.

Signs of Improper Rebound Settings

  • Too fast rebound: The car feels bouncy, especially after hitting a bump. The rear end may skip sideways over undulations, and the car may feel unstable under hard braking.
  • Too slow rebound: The car feels sluggish and "planted" but in a vague way. After cornering, the suspension takes too long to return to level, causing delayed response to steering inputs. Over consecutive bumps, the suspension becomes stiffer as it packs down.

Setting Rebound for Different Driving Conditions

On smooth racetracks, faster rebound helps the suspension return quickly between turns, improving responsiveness. On bumpy roads, slower rebound prevents the suspension from extending too fast and losing contact with the pavement. For street driving, a balance between control and compliance is ideal. A common recommendation is to start near the middle of the adjustment range, then test by driving over a known bumpy section. Adjust two clicks stiffer at a time until the bounciness disappears without making the ride harsh.

Spring Tension Explained

Spring tension refers to the stiffness of the coil spring, determined by its spring rate. The spring rate is the amount of force required to compress the spring one inch. A 300 lb/in spring requires 300 pounds to compress it one inch. The spring rate, combined with the vehicle's corner weight, determines the suspension's natural frequency and static ride height.

Spring Rate and Ride Quality

Higher spring rates produce stiffer suspension, which reduces body roll and weight transfer during cornering. This improves grip and stability in high-speed maneuvers. However, stiffer springs transmit more road vibration to the chassis, reducing comfort. Lower spring rates provide a smoother ride at the expense of more body roll and less precise handling. The goal is to choose a spring rate that matches your driving needs and vehicle weight.

For a typical street car, spring rates between 200-400 lb/in are common on the front and 150-300 lb/in on the rear, depending on weight distribution. Track-focused cars often run 400-800 lb/in or higher. Beginners should favor softer rates initially and increase stiffness as their driving skills and understanding of chassis dynamics develop.

Spring Preload: What It Is and Why It Matters

Spring preload is the amount of initial compression applied to the spring when the suspension is at full extension. Preload does not change the spring rate, but it does affect the ride height and the amount of force required to begin compressing the suspension. Some coilovers allow preload adjustment by rotating the spring seat. Adding preload raises the car slightly and increases the force needed to start compression. Reducing preload does the opposite.

It is important to avoid excessive preload, which can cause the spring to coil bind at full compression, damaging the suspension and creating a harsh ride. As a rule, set preload so that the spring is snugly seated with light tension at full droop, then use ride height adjustment to achieve the desired height.

Coilover Adjustability: Compression, Rebound, and Ride Height

Ride Height Adjustment

Lowering the ride height lowers the vehicle's center of gravity, reducing body roll and improving aerodynamics. It also changes suspension geometry, which can affect camber, caster, and bump steer. Dropping a car too much can cause control arms to angle upward, leading to poor bump travel and reduced grip. A modest drop of 1 to 2 inches is typical for street performance cars. Always verify alignment after changing ride height.

Damping Adjustments

Most coilovers offer damping adjustability via a knob or screw on the shock body. Some provide separate adjustment for compression and rebound; others combine them into a single adjustment. Entry-level coilovers may have fixed damping, while high-end units offer independent high-speed and low-speed adjustment for both compression and rebound.

When adjusting damping, make small changes. A general method is to set all dampers to their softest setting, then drive the car on a familiar road. Gradually stiffen the compression and rebound together until the car feels controlled without being harsh. Then fine-tune each corner individually to balance the car's behavior in left and right turns.

Types of Coilovers: Street vs Track vs Rally

Street Coilovers

Designed for daily driving, street coilovers prioritize ride comfort and durability. They typically have softer spring rates (200-400 lb/in), moderate damping adjustment, and corrosion-resistant materials. Many include rubber top mounts to reduce noise, vibration, and harshness (NVH). Brands like BC Racing, Tein, and KW offer popular street coilover kits.

Track Coilovers

Track coilovers are built for maximum performance on smooth surfaces. They feature stiffer springs (400+ lb/in), more aggressive damping curves, and metal pillow ball mounts for precise steering feedback. They may lack provisions for street comfort and often require periodic rebuilds. Brands like Ohlins, Moton, and JRZ are common in competitive motorsports.

Rally and Off-Road Coilovers

Rally coilovers are designed for rough terrain and high suspension travel. They feature heavy-duty construction, remote reservoirs for increased oil volume, and high-speed compression adjustability to handle large impacts. Spring rates are often progressive to maintain comfort over uneven surfaces. Brands like Reiger, Proflex, and AST are popular in rallying.

For most beginners, a quality street-focused coilover is the best choice. It offers the adjustability needed to learn suspension tuning without the harshness and maintenance demands of race-spec equipment.

Common Coilover Mistakes Beginners Make

Lowering Too Much Too Quickly

One of the most common errors is slamming the car as low as possible for looks without considering suspension geometry. Excessive lowering can cause the control arms to angle sharply, reducing grip, increasing tire wear, and bottoming out the suspension over bumps. Always maintain enough suspension travel to avoid hitting the bump stops during normal driving.

Ignoring Corner Balance

Coilovers allow you to adjust ride height independently at each corner, but setting them all to the same perch height does not guarantee equal corner weights. A corner balance scales the car to ensure diagonal weight distribution is even, improving handling balance. This is especially important for track use but also beneficial for street cars. A professional corner balance is worth the investment.

Mixing Spring Rates Improperly

Using mismatched spring rates between the front and rear can create unpredictable handling. A rear spring that is too stiff relative to the front can cause snap oversteer. A front spring that is too soft can produce excessive understeer. Stick to spring rate pairs recommended by the manufacturer or consult with suspension professionals.

Neglecting Regular Maintenance

Coilovers require periodic inspection and maintenance. Common issues include oil leaks from damper seals, worn bushings, and corrosion on threaded bodies. Clean the threads regularly and apply anti-seize to prevent seizing. Inspect for leaks every few months. Track users should plan for damper rebuilds every 20,000-30,000 miles or sooner if performance degrades.

How to Choose the Right Coilovers for Your Car

Start by defining your driving goals. Daily driver? Weekend canyon carver? Track enthusiast? Your budget and expectations will guide the choice. For a first set of coilovers, aim for a mid-range kit from a reputable brand. Avoid ultra-budget options, as poor damping control and durability issues can create safety risks. Look for features like stainless steel bodies, threaded adjustment, and corrosion-resistant hardware.

Consider the spring rate range offered. A kit that allows spring changes is more versatile than one with fixed springs. Also check the damping adjustment range. A good rule: the kit should offer at least 20 clicks of adjustment to give you meaningful tuning range. Read reviews from owners who use the car similarly to how you plan to drive yours.

For further reading, check out Racecar Engineering's Coilover Buyer's Guide for technical insights on damper selection. The Turnology Beginner's Guide to Coilovers offers practical setup advice. For spring rate calculators and suspension math, QA1's Spring Rate Calculator is a useful tool.

Installation Considerations

Installing coilovers is a moderate-to-advanced DIY job. It requires basic hand tools, spring compressors, and a torque wrench. However, proper installation also involves removing suspension components, compressing springs safely, and torquing fasteners to spec. If you are not comfortable with suspension work, hire a professional. An improperly installed coilover can detach while driving, causing loss of control.

After installation, a wheel alignment is mandatory. The ride height change will alter camber, caster, and toe. Drive the car for a few days to allow the suspension to settle, then get an alignment. Many shops will perform a corner balance and alignment together for a better handling result.

Breaking In Your Coilovers

New coilovers require a break-in period. Drive the car normally for 200-500 miles to allow the damper seals and internal components to seat. During this period, avoid aggressive driving or setting the dampers to extreme positions. After break-in, recheck ride height and fasteners, then adjust damping to your preference.

Conclusion

Coilovers are one of the most impactful upgrades you can make to a car's handling, ride quality, and appearance. By understanding compression, rebound, and spring tension, you gain the ability to tailor your suspension to your exact driving style and conditions. Start with conservative settings, make incremental adjustments, and document your changes to learn what works. Whether you are lowering your daily driver for a sportier look or setting up a dedicated track car, mastering these fundamentals will help you get the most from your coilover investment.