FOX vs KING
OEM FIT COILOVERS
It’s a question we hear all the time. In this article, we’ll break down some of the key differences between the two brands to help you understand how they compare. Our goal is to provide clear, helpful information so YOU can make the best choice based on your budget, build, and how you use your vehicle.
*Before reading, the coilover examples we will be referencing are:
Vehicle: 2016-2023 Toyota Tacoma
Shocks: Front Extended length coilovers (most common)
Fox 2.5 Coilover, Remote Reservoir 0-3” Extended length with DSC (FOX-880-06-418)
Compressed Length: 17.59″ | Extended Length: 22.48″
King 2.5 Coilover, Remote Reservoir 0-3” Extended length with Adjuster (KRS-25001-119A-EXT)
Compressed Length: 17.3″ | Extended Length: 22.6″
Springs
FOX: The springs come in a silver finish, matching the look of Eibach’s full line of silver coil springs. If different rates are needed, AccuTune Offroad offers a wide range of Eibach options made from high-quality wire using precision manufacturing processes. Heavier rate springs are not included and must be purchased separately.
KING: These shocks come with blue springs, and blue replacement springs are available directly from King. Silver Eibach springs are also compatible and offer a great look with high-quality performance. If heavier rate springs are needed, shocks can be special ordered with upgraded spring rates at no additional charge.
Shock Body
FOX: These shocks feature a durable steel body with a zinc plating finish to help resist corrosion and extend longevity in harsh conditions.
KING: These shocks feature a strong steel body with cadmium plating, offering enhanced corrosion resistance and a rugged finish designed to withstand demanding environments.
Notes: Both zinc and cadmium plating offer similar levels of corrosion resistance, helping to protect the steel shock body from rust and wear in harsh conditions. The choice typically comes down to manufacturer preference and finish appearance.
Shafts / Piston Rods
FOX: 17-4 H900 Stainless Steel, Surface Hardened, 45 HRC
KING: 1045/1050 Steel Chrome Plated, Through Hardened, 23 HRC
One of the most common issues we see with shocks is oil leakage, typically caused by a damaged piston shaft. When the shaft gets nicked or gouged—often from sand, rocks, or road debris—it can cut into the seals and lead to fluid loss. That’s why surface hardness is so important. A harder shaft is more resistant to damage and better able to withstand impacts over time.
The Fox stainless steel shafts are a standout in this area—they’re about twice as strong as King’s shafts and can handle significantly more abuse. This added durability helps protect the seals and extend the life of the shock.
Hardness is measured on the Rockwell C (HRc) scale, which evaluates how deeply a steel surface can be indented under a specific force. The less it deforms, the higher (and harder) it rates on the scale. In the case of shock shafts, a higher HRc means better resistance to surface damage—and ultimately, better long-term reliability.
Pistons
FOX: Fox uses linear piston designs in their shocks, which provide a consistent and predictable damping curve throughout the range of travel. This allows for smoother control and a more balanced ride, especially when paired with custom valving. While some factory shocks may come with digressive characteristics, Fox’s linear pistons are ideal for tuning a wide range of setups making them a great choice for drivers seeking comfort, stability, and performance across mixed terrain.
KING: These shocks are designed with a linear compression curve, offering consistent and predictable damping throughout the suspension travel. While some shocks may come with digressive valving from the factory providing firm low-speed response and softer high-speed absorption—we revalve them to a linear setup for improved ride quality, better control, and smoother transitions over varying terrain. This tuning approach is ideal for drivers who want balanced performance both on and off-road.
Shock Seals
FOX: Buna
KING: Buna & Urethane
Both shocks feature high-quality urethane wipers. Fox employs two Buna main seals, while King uses a main Buna O-ring paired with a urethane secondary U-cup. The King sealing system generates significantly higher friction, which can negatively impact ride quality. To counteract this, King charges their shocks to 150 psi, but this higher pressure can lead to cavitation problems.
Shock Oil
FOX: Conventional Oil, rated up to 400F, viscosity index of 370
KING: Conventional Oil, rated 14 to 230 F, viscosity index of 150
Fox oil provides significantly better lubrication across a wide temperature range and is far more resistant to heat-related breakdown. High lubricity and thermal stability are essential for long-lasting performance. The viscosity index (VI), which indicates how much damping fades with heat, is 370 for Fox—an exceptionally high rating that ensures consistent performance. In contrast, King’s VI of 150 is average, making their shocks more susceptible to fade when temperatures rise.
Bearings & Bushings
FOX: Fox coilovers use FK Rod Ends bearings at both the top and bottom, sealed with an O-ring for enhanced durability. In comparison, OEM-fit Smoothie shocks primarily use bushings.
KING: King shocks feature bearings in all mounts except for stud mounts.
Notes: In corrosive environments, bushings tend to be more durable and easier to replace. However, in racing conditions, bearings offer greater durability and performance.
Internal Top Out
FOX: At full extension, Fox shocks feature a rubber top-out bumper that prevents hard metal-to-metal contact. This rubber bumper reduces noise and smooths out the stroke, offering a noticeable improvement—especially on lifts of two inches or more.
KING: At full extension, King shocks use internal metal-on-metal stops. While this doesn’t damage the shock, it can be felt and heard when the shock reaches full extension.
Remote Reservoir Hose Fittings
FOX: Uses -6 hose fittings with a combination of hard 90° and soft 90° fittings.
KING: Also uses -6 hose fittings with hard 90° and soft 90° fittings.
Notes: Larger hoses allow better oil flow and improve ride quality. The -6 hose (3/8″ tube ID) is sufficient for this application.
Remote Reservoir Hoses
FOX: Black cloth-wrapped hose.
KING: Blue rubber hose with white label printing.
Notes: Both hoses offer similar strength. However, King’s hose is easier to handle and makes mounting the reservoir simpler.
Reservoir Mounts
FOX: Yes, mounts using OEM bolts. Black powdercoated
KING: Yes, mounts using OEM bolts, silver finish with zinc plating
Shock Adjusters
FOX: DSC (Dual Speed Compression) adjuster: Enables manual adjustment of both high-speed and low-speed compression settings. [TECH about DSC Adjusters]
KING: Mid-Speed Adjuster: Single knob that allows adjustment of mid-speed compression.
[TECH about King Adjusters]
Shock Tuning
Both Fox and King OEM coilovers come with soft valving by default, which can result in a bouncy ride and less-than-ideal handling. While this setup may be acceptable for mostly stock vehicles without additional modifications, we believe there’s significant potential for improvement.
Depending on your vehicle and how you plan to use it, we can custom valve your shocks to deliver the ultimate performance tailored to your needs.
If you’re interested in having your Fox or King shocks professionally custom valved, contact us today to learn more:
(619) 722-8555 | Sales@AccuTuneOffroad.com
SUMMARY:
Both Fox and King offer excellent OEM shocks that can be tuned, rebuilt, or upgraded. Rebuild kits are typically stocked by suspension shops or readily available from the manufacturers.
So, what might make you choose one over the other?
Fox is one of the largest shock manufacturers in the off-road industry, producing shocks for everything from mountain bikes and snowmobiles to factory-equipped trucks like the Ford Raptor and Jeep Rubicon. Fox uses superior seals, shock oil, and shafts, making them a premium, albeit more expensive, option. Their shafts are more durable, featuring surface hardening that stands up well to harsh conditions like snow and road salt. Fox’s DSC adjuster is among the most advanced on the market, allowing precise tuning for towing or fine adjustments.
King Shocks is a renowned, family-owned brand that’s 100% designed, manufactured, and assembled in the USA since 1996. Known for their high-performance race shocks, King brings trophy truck technology to their OEM line at a reasonable price. Their anodized blue components make a bold statement, and their shocks are easily tunable, rebuildable, and upgradeable to fit your needs.
Both brands have unique strengths, and with AccuTune’s expert tuning, either choice will deliver outstanding performance.
Related Tech Articles
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Should I Get DSC Adjusters?
