You: “Should I get Fox Shocks or King Shocks for my Bronco?”
AccuTune Offroad: “Yes!”
It’s a common question, but there isn’t a one-size-fits-all answer. In this article, we’ll break down some of the key differences between Fox and King shocks for 2021+ Ford Broncos. Our goal is to give you the information you need to make the best decision for your budget, build, and lifestyle. At AccuTune Offroad, we can custom-valve either option to match your specific Bronco and driving style. Whether your Bronco is a daily driver, a prerunner, or your go-to adventure rig, we’ll tune your shocks to deliver the performance you need.
FRONT Fox Shocks (2 or 4 door 2021+ Bronco)
P/N: FOX-883-06-212 or FOX-883-06-209
Compressed Length: 18.79 “ | Extended Length: 24.26”
Total Shock Travel: 5.47”
Max recommended shock length at ride height: 22.50”
Note: Both part numbers share the same lengths
REAR Fox Shocks (2 or 4 door 2021+ Bronco)
P/N: FOX-883-06-213 or FOX-883-06-210
Compressed Length: 19.24” | Extended Length: 27.21”
Total Shock Travel: 7.97”
Max recommend shock length at ride height: 23.00”
Note: Both part numbers share the same lengths
FRONT King Shocks (2 or 4 door 2021+ Bronco)
P/N: KRS-25001-392 or KRS-25001-392A
Compressed Length: 18.50 “ | Extended Length: 24.60”
Total Shock Travel: 6.10”
Note: Extended lengths are too long & cause issues, read below for our solution
Max recommended shock length at ride height: 22.50”
Note: Both part numbers share the same lengths
REAR King Shocks (2 or 4 door 2021+ Bronco)
P/N: KRS-25001-393 or KRS-25001-393A
Compressed Length: 18.50” | Extended Length: 27.00”
Total Shock Travel: 8.50”
Max recommend shock length at ride height: 23.00”
Note: Both part numbers share the same lengths
Fox Coil Springs
FOX shocks for the Bronco come in their signature silver finish. If you need new spring rates, Eibach offers a full line of high-quality silver springs made with precision wire and top-tier manufacturing. Heavier rate springs are available separately.
Stock Spring Specs (Both 2-Door and 4-Door Models):
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Front Springs: 16.55″ x 3.630″ x 365 lb
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Rear Springs: 15.50″ x 3.570″ x 185 lb
The stock FOX rear coilover springs are too soft for both 2-door and 4-door Broncos, even at stock weight. At AccuTune Offroad, we offer spring rate options tailored to your Bronco’s weight and setup, ensuring optimal performance and ride quality.
King Coil Springs
KING coilovers for the Bronco come in their signature blue finish. Replacement blue springs are available from King, and coilovers can often be special ordered with heavier rate springs (if available) at no additional charge, though this may increase lead time. Silver Eibach springs are also compatible and provide a clean look.
Stock Spring Specs:
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Front Springs: 16.00″ x 3.00″ x 550 lb
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Rear Springs: 4.00″ x 3.00″ x 500 lb / 14.00″ x 3.00″ x 350 lb (Combined rate: 206 lb/in)
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Updated 8/23: Rear spring is Progressive 16.6” with rates of 167 lb / 225 lb
KING spring rates have shown strong performance results and are well-suited for both 2-door and 4-door Broncos, providing excellent ride quality and support even with heavier setups.
Shock Body
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FOX: One-piece 6061-T6 aluminum, hard-anodized
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KING: Steel body with zinc plating and aluminum top cap
Both FOX and KING shocks are built strong and durable for extreme off-road use. The FOX hard-anodized aluminum bodies resist corrosion far better than zinc-plated steel and excel at dissipating heat when pushing your Bronco hard on fire roads or desert trails. KING’s steel bodies are tough and reliable, offering solid performance, though they don’t dissipate heat or resist corrosion quite as efficiently as FOX’s aluminum design.
Shock Shaft Bumpers
Both FOX and KING coilovers include shaft-mounted bump stops, which serve as the primary bump stops on a Bronco since these trucks don’t have traditional frame-mounted bump stops like other vehicles. KING’s bump stops perform very well, providing consistent support and preventing harsh bottom-out events. FOX’s stock bump stops, however, are too soft, which can make bottoming out feel abrupt. At AccuTune Offroad, we offer upgraded bump stops for FOX coilovers to better control bottom-out events and improve overall ride quality.
Shafts / Piston Rods
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FOX: 1045 steel, chrome plated
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KING: 1045/1050 steel, chrome plated, through hardened
KING rear shocks on the Ford Bronco also include shaft guards, providing extra protection for the shafts and springs against debris and sand thrown up by the front tires. Both FOX and KING shafts are durable and designed to handle extreme off-road conditions, but KING’s through-hardened steel and added guards give extra durability and protection for aggressive off-road use.
Fox Pistons
The stock Bronco coilover shocks, front and rear, come with powder metal pistons. While functional, we’ve found that these pistons can make the Bronco feel too soft and less controlled than it could be. The main difference between piston designs is how much oil can flow through them, which affects damping performance. Both designs have their benefits, but for this application, we prefer the 9-Hole Race Piston. AccuTune Offroad’s Custom Upgrade Package includes 9-Hole Race Pistons, delivering improved ride quality, better control, and overall enhanced performance for your Bronco.
King Pistons
Rear KING shocks on the Ford Bronco come stock with digressive pistons. Digressive valving is designed to provide a firmer ride by allowing less oil flow at low speeds and more at high speeds. While this can be beneficial in certain off-road scenarios, many customers find it too harsh for everyday driving. For a smoother, more controlled ride, we recommend switching to KING’s standard linear pistons—the same design used in the front coilovers.
This simple upgrade, combined with AccuTune Offroad’s custom valving, significantly improves ride quality and overall performance. AccuTune offers this Linear Piston upgrade to help your Bronco deliver a more balanced, comfortable, and capable driving experience both on and off-road. Learn more about Digressive Valving HERE
Shock Seals
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FOX: Buna seals, dual main seals, high-quality shaft wiper
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KING: Buna main o-ring with urethane secondary u-cup, high-quality shaft wiper
Both FOX and KING shocks use high-quality shaft wipers to keep dirt and debris off the shaft. FOX employs two Buna main seals, providing smooth operation with minimal friction. KING’s sealing setup—with a Buna main o-ring and urethane secondary u-cup—offers excellent durability but can introduce more friction, which may slightly affect ride quality.
Shock Oil
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FOX: Conventional oil, rated up to 400°F, viscosity index (VI) of 370
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KING: Conventional oil, rated 14–230°F, viscosity index (VI) of 150
FOX shock oil provides superior lubrication across a wide temperature range and is far less likely to break down under heat. High lubricity and thermal stability are essential for maintaining long-lasting performance. The viscosity index (VI) indicates how much damping can fade as the shock heats up. With a VI of 370, FOX shocks maintain consistent damping even under extreme conditions, delivering exceptional performance. KING’s VI of 150 is average, meaning their shocks are more prone to fade when temperatures rise during aggressive driving or extended off-road use.
Internal Top Out
Both FOX and KING shocks feature an internal rubber top-out bumper when fully extended. This rubber bumper prevents hard metal-to-metal contact, helping the shocks operate more quietly and smoothly. It also cushions the suspension when it fully droops over rough terrain, improving ride comfort and protecting the components from unnecessary stress.
Remote Reservoir Hose Fittings
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FOX: -8 hose fittings, using hard 90° and soft 45° fittings. Note that the reservoir fitting may limit the full adjustment range on the preload collar.
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KING: -8 hose fittings, using soft 90° fittings.
Larger diameter hoses allow more oil flow, which generally improves ride quality. For Bronco coilovers, -8 hose fittings (1/2″ tube ID) are sufficient to provide proper flow and performance.
Remote Reservoir Hoses
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FOX: Black rubber hydraulic hose
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KING: Blue rubber hose with white label writing
There’s no significant difference in strength between the two hoses. However, KING’s hose is more flexible, making it easier to route and mount the reservoir during installation.
Fox, Front Reservoir Mount
The FOX front remote reservoir is mounted on a bracket behind the inner fender. This location keeps it well-protected from potential damage, though it can be a bit difficult to access for adjustments or maintenance. One of the biggest advantages of this placement is tire clearance—no matter how large your tires are, the remote reservoir is positioned so it won’t come into contact with them, ensuring both safety and reliability on and off-road.
King, Front Reservoir Mount
KING mounts their front remote reservoir low on the frame, which is a traditional location for many of their OEM-style coilovers. While functional, this placement can be problematic on Broncos that have been modified to fit larger tires, as the standard KING reservoir mount may interfere with tire clearance and won’t work without adjustments.
Fox, Rear Reservoir Mount
The FOX rear remote reservoir is tucked under the inner fender, with the DSC adjuster knobs facing downward. This placement makes it easier to access compared to the front reservoir, allowing for simpler adjustments and maintenance. (Note: the inner fender liner is removed in this photo for clarity.)
King, Rear Reservoir Mount
KING rear shock reservoirs are mounted parallel to the frame, following their traditional layout used on most other coilovers. A single reservoir clamp is used, which can make installation faster and simpler. The compression adjuster is easy to reach, and the reservoir’s positioning provides a great location for branding visibility.
Shock Adjusters
FOX: DSC, Dual Speed Compression adjuster. Allows you to manually adjust the high speed and low speed compression. [TECH about DSC Adjusters]
KING: Mid Speed Adjusters. One knob to adjust mid speed compression.
[TECH about King Adjusters]
King, 2021+ Bronco Installation Guide
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The KING reservoir placement, both front and rear, is generally more accessible than FOX’s design, making adjustments and maintenance easier.
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The Bronco used for testing had a body mount delete kit installed, which provides additional clearance for the reservoirs.
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Be cautious with the front KING coilovers: their length is slightly too long for the OEM CV axles—approximately 5/16″ over what the CVs can reliably handle. Extra care is needed when handling the CV axles during installation.
Fox, 2021+ Bronco Installation Guide
Install Tips & Tricks from AccuTune Offroad
FOX Front Coilovers
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The instructions suggest removing the wheel well liner, but in our experience, it’s not always necessary.
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Installing the reservoir clamps can be challenging due to the tight space in the wheel well.
Tip: Loosely attach the reservoir to the bracket first, then install the bracket with the reservoir onto the vehicle. This method is easier than following the sequence in the installation guide. -
Avoid using an impact gun on the sway bar link nut, as it can gall easily.
FOX Rear Coilovers
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Removing the wheel well liner, as suggested in the instructions, makes removing the old coilover and installing the FOX coilovers much easier—especially when handling the reservoir.
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The “speed nuts” used to attach the reservoir bracket to the frame can be finicky. They may need to be compressed with pliers before mounting on the backing plate, and even then, they fit loosely, making installation more difficult than it should be.
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Installing the reservoir clamps in the rear is also tricky due to limited space.
Tip: Loosely attach the reservoir to the bracket first, then install the bracket with the reservoir onto the vehicle for an easier process.
AccuTune Offroad Upgrade Options
AccuTune Offroad Upgrade Package:
This upgrade package includes FOX Race Pistons, new Eibach bump stops front and rear, and Eibach coil springs for the rear coilovers. Correct spring rates help properly support your Bronco’s weight, while AccuTune Offroad’s custom valving combined with FOX 9-Hole Race Pistons significantly improves ride quality. This package is a must-have for anyone looking to achieve the best ride quality on a 2021+ Ford Bronco. We offer upgrade packages for 2-Door Bronco and 4-Door Bronco.
AccuTune Offroad Upgrade Package:
For the smoothest ride with KING shocks on your Ford Bronco, we highly recommend upgrading the rear shock pistons to linear pistons. This simple change provides a much smoother ride both on the street and off-road. The front shocks already come with linear pistons, so the upgrade is only necessary in the rear.
For the front shocks, we suggest adding our “CV Saver” modification. This limits the front shocks by approximately 0.30″, preventing CV axles from binding at full droop. This adjustment is easily performed while the shocks are opened for custom valving, ensuring optimal performance and durability.
FOX vs. KING Shocks: What Sets Them Apart
Both FOX and KING offer excellent suspension products for the OEM and aftermarket off-road market. Most of their shocks can be tuned, rebuilt, or upgraded, with rebuild kits typically stocked by suspension shops or easily acquired from the manufacturer. So how do you choose one over the other?
FOX Shocks
FOX is arguably the largest and most recognized shock manufacturer in the off-road industry, with a reputation spanning everything from mountain bikes, snowmobiles, and UTVs to Trophy Trucks and factory options on vehicles like the Ford Raptor, Jeep Rubicon, Ford Bronco, Polaris RZR, and CanAm X3. FOX uses high-quality materials, making their shocks more expensive than many competitors, but the investment reflects the performance and durability you get. Their DSC adjuster is one of the most advanced shock adjusters available, allowing precise tuning for towing or fine adjustments. FOX Performance Elite Series shocks come standard with DSC adjusters and aluminum bodies to prevent corrosion.
At AccuTune Offroad, our engineers spent weeks testing and tuning FOX shocks to optimize comfort and performance. Standard tuning reduces road feel and smooths out small bumps, while our upgrade package—including enhanced bump stops, pistons, and springs—delivers significant improvements in ride quality, bottom-out resistance, and overall performance. If you value high-quality shocks with advanced adjustability and premium materials, FOX is an excellent choice.
KING Shocks
KING Shocks is a well-known, family-owned shock brand in the off-road world, designed, manufactured, and assembled in the U.S.A. since 1996. KING’s high-performance shocks are found on top-tier race trucks worldwide, and their OEM-fit shocks bring race-proven technology to daily drivers at a reasonable price. KING coilovers come with proper spring rates, rear shock shaft guards, and finned reservoirs, all finished in their iconic anodized blue aluminum for both performance and style. Many race components carry over into their OEM line, allowing your daily driver to benefit from Trophy Truck technology.
When tuning KING shocks, AccuTune Offroad focused on valving adjustments and rear piston replacements. These modifications yielded a much smoother highway ride with less vibration, improved control over bigger bumps, and better bottom-out performance. One issue we encountered was front CV joints binding due to the shock lengths being slightly too long, which even caused CV failures on our test vehicle. To solve this, we offer CV Savers that can be installed inside the front shocks to prevent binding. If you want a shock that combines outstanding performance with iconic off-road style, KING is the package for your Bronco.
The Bottom Line
Both FOX and KING offer tunable, rebuildable, and high-performance shocks, but the choice comes down to your priorities. FOX delivers premium materials, advanced adjustability, and a reputation for performance across a wide range of vehicles. KING brings race-proven tech to your daily driver, with strong performance, great aesthetics, and a slightly more affordable price point. AccuTune Offroad can custom-tune either option for your 2021+ Ford Bronco, ensuring optimal ride quality, comfort, and capability no matter which brand you choose.
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Custom Shock Tuning
If your interested in having you Fox or King Shocks custom valved, contact us today to learn more (619) 722-8555 | Sales@Accutuneoffroad.com
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