You: “Should I get Fox Shocks or King Shocks for my Bronco?”
AccuTune Offroad: “Yes!”

This common question is pretty broad, so in this article we will go through some of the main differences between the two brands and the shocks they offer for a 2021+ Ford Bronco. This article is intended to educate and allow YOU as the customer to make the best decision for your budget, build and lifestyle. AccuTune Offroad will custom valve either option for your specific Bronco and how you plan to drive it. Whether you use your Bronco as a daily driver, prerunner or to venture off and explore the outdoors, we can tune for your needs.

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

*See below for Recommended Upgrades from AccuTune Offroad

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

*See below for Recommended Upgrades from AccuTune Offroad

  • Kit: 21+ Ford Bronco, King 2.5 Coilovers W/Adjusters, Shock Package

    From: $4,732.00


  • Kit: 21+ Ford Bronco, Fox 2.5 Performance Elite Series Coilover Shock Package, DSC



Fox Coil Springs

FOX: Silver color. Eibach has a full line of silver springs if new rates are needed. They use high quality wire & manufacturing. Heavier rate springs need to be purchased separately.

Spring rates below are for both 2-door and 4-door models.

Front Springs: 16.55″ x 3.630″ x 365lb

Rear Springs: 15.50″ x 3.570″ x 185lb”

Fox spring rates for the rear coilovers are too soft and are not ideal for 2-door and 4-door models, even with stock weight. AccuTune Offroad has spring rate options depending on the weight of your Bronco.

King Coil Springs

KING: Blue color. Blue replacement springs are available from King. King Coilovers can be special ordered with heavier rate springs (if available) for no additional charge, but may have a longer lead time. Silver Eibach springs also fit and look great.

Front Springs: 16.00″ x  3.00″ x 550lb

Rear Springs: 4.00″ x 3.00″ x 500lb / 14.00″ x 3.00″ x 350lb / Combined rate: 206lbs/in
*Update 8/23: Rear spring is Progressive 16.6”  Rate’s 167lb / 225lb

Spring rates on King’s Bronco shock have provided positive results and will work well for both 2 & 4 Door models.

Shock Body

FOX: One-piece 6061-T6 Aluminum hard anodized

KING: Steel Body, Zinc plating, aluminum top cap

Both shock bodies are strong and durable for extreme off-road use. The hard-anodized aluminum one piece bodies resist corrosion a lot better than their zinc-plated steel counterparts, and they are also better at dissipating heat when you are blasting fire roads.

Shaft Bumpers

Both Fox and King have shaft bump stops. These are the main bump stops on the suspension for a Bronco since they do not have a frame mounted bump stop traditionally found on other vehicles. Kings bump stop works great, while the Fox bump stop is too soft making bottom out events too harsh. AccuTune Offroad offers upgraded bump stops for the Fox coilovers that will help prevent bottom out events from being too harsh.

Shafts / Piston Rods

FOX: 1045 Steel Chrome Plated
KING: 1045/1050 Steel Chrome Plated, Through Hardened
King rear shocks on the Ford Bronco come with shaft guards which will help protect the springs and shafts from getting sand blasted from the front tires. 

Fox Pistons

The powder metal piston comes standard on these Bronco coilover shocks front and rear. With these pistons, we found the Bronco feeling too soft and not as controlled as it could be. The main difference between these two pistons has to do with the amount of oil that can flow through it. There are benefits to each design, but for this application we prefer 9-Hole Race Piston. The AccuTune Custom Upgrade package comes with 9-Hole Race Pistons for better ride quality & overall performance.

King Pistons

Rear King shocks for the Ford Bronco come standard with Digressive Pistons. [more info on digressive valving] This type of valving tends to offer a more firm ride that has not been desirable from our customers. For a smoother ride, we recommend switching to one of King’s standard Linear Pistons. This same piston already comes standard in the front coilovers. This simple upgrade, along with AccuTune’s valving will make a big improvement on ride quality. AccuTune Offroad offers this Linear Piston as an upgrade for even better ride quality & overall performance.

Shock Seals

FOX: Buna
KING: Buna & Urethane
Notes: Both shocks use a high quality shaft wiper. Fox uses two Buna main seals. King uses a main Buna o-ring and urethane secondary u-cup. The King sealing package has more friction which can cause issues with ride quality. 

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

Notes: Fox oil offers substantially better lubrication across a wide range of temperatures, and is less likely to break down due to heat. High lubricity and resistance to breaking down are critical for a long lifespan. Viscosity index (VI) is a measure of how much the damping will fade due to heat.  Fox’s VI of 370 is very high and provides exceptional performance.  King’s VI of 150 is an average rating which means it is much more prone to shock fade when getting hot.


Internal Top Out

FOX & KING: When the shocks are fully extended, both Fox and King shocks have an internal rubber top out bumper that prevents hard metal to metal contact. This rubber bumper help the shocks be quieter and smoother when the suspension fully droops out over rough terrain. 

Remote Reservoir Hose Fittings

FOX: -8 hose fittings, using hard 90s and soft 45 degree fittings.
Reservoir fitting may not allow full adjustment range on preload collar.

KING: -8 hose fittings, using soft 90 degree fittings.

Bigger hoses flow more oil and ride better. -8 hose is adequate for this application. (-8 Hose Fitting = 1/2″ Tube ID)

Remote Reservoir Hoses

FOX: Black rubber hydraulic hose

KING: Blue rubber with white label writing

Notes: No real difference in strength. King hose is easier to manipulate and mount the reservoir.

Fox, Front Reservoir Mount

Fox front remote reservoir is mounted to a bracket that sits behind the inner fender. It’s certainly out of the way from getting damaged, but may be a little too hard to access. A huge benefit to this location, is tire clearance. No matter what size tires you plan to shove into this fender, the remote reservoir should never be at risk of getting hit with the tire.

King, Front Reservoir Mount

King mounts their front remote reservoir down low on the frame, which is a traditional location for most of their OEM fit coilovers. Unfortunately this is in a spot that is commonly modified to fit larger tires and the standard reservoir mount from King will not work.

Fox, Rear Reservoir Mount

Fox rear remote reservoir is tucked up under the inner fender, with DSC adjuster knobs facing down. This location is easier to access than the front.
Note: inner fender liner is removed in this photo.

King, Rear Reservoir Mount

King rear shock reservoirs are mounted parallel with the frame, again in a traditional fashion like they do with most other shocks. There is only a single reservoir clamp used, which can make the install a bit quicker. Compression adjuster is easy to access and branding location is perfect.

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

Install Tips & Tricks from AccuTune Offroad:
-The reservoir placement for both front and rear were much more accessible than Fox.
-Bronco we used for testing had the body mount delete kit on it and that affords more room for the reservoir.
-King’s front coilover length is too long for the OEM CV axles. I think they’re approximately 5/16″ longer than what the CV’s can reliably handle. So be careful when handling the CV axles.

Fox, 2021+ Bronco Installation Guide

Install Tips & Tricks from AccuTune Offroad:

Fox Front Coilovers
-Instructions suggest removing the wheel well liner, but we didn’t find it necessary.
-The reservoir clamps are very difficult to install, especially within the confines of the wheel well.
Tip: Loosely install the reservoir onto the reservoir bracket, and then install the bracket with the reservoir onto vehicle. This is instead of installing the reservoir earlier on in the installation guide.
-Do not use an impact gun to remove the sway bar link nut, as it tends to gaul easily.
Fox Rear Coilovers
-Instructions suggest removing the wheel well liner, and it makes removing the old coilover and installing the Fox coilovers much easier, especially the reservoir!!
-The “speed nuts” used to fasten the reservoir bracket to the frame, are finicky. They likely have to be squished with pliers before installing them on the backing plate, and even then, they fit loosely which makes installation harder than it should be.
-The reservoir clamps are very difficult to install, especially within the confines of the wheel well.
Tip: Loosely install the reservoir onto the reservoir bracket, and then install the bracket with the reservoir onto vehicle. This is instead of installing the reservoir earlier on in the installation guide.

AccuTune Offroad Upgrade Options

AccuTune Offroad Upgrade Package:

This option includes Fox Race Pistons and new Eibach Bump Stops front and rear along with new Eibach coil springs for the rear coilovers. Proper spring rates will help support the vehicle weight, while AccuTune Offroad custom valving with Fox 9-Hole Race Piston really makes a big improvement on ride quality. This is a must have if you want the best ride quality on your 21+ Ford Bronco. We offer upgrade packages for 2-Door Bronco and 4-Door Bronco.

AccuTune Offroad Upgrade Package:

For the best riding King shocks on your Ford Bronco, we highly recommend upgrading pistons in the rear shocks. Switching to a linear piston will offer a much smoother ride on the street & off-road. Front shocks already come with this piston, so the upgrade is only needed in the rear. For the front, we recommend adding our “CV Saver”. This modification will limit the front shocks about .30″ to keep the cv axles from binding at full droop. This simple modification will be added while we have the shock opened up to replace the valving.


Both Fox and King have great suspension products to offer the OEM market. Most of their shocks can be tuned, rebuilt or upgraded. Rebuild kits are usually stocked by suspension shops or can be easily acquired from the manufacturer. So what are some things that would make you pick one over the other?

Fox is considered one of, if not the largest shock manufacturer in the off-road industry. They have a strong reputation for making shocks for everything from Mountain Bikes, Snowmobiles, UTVs, and Trophy Trucks to Factory options on trucks like the Ford Raptor, Jeep Rubicon, Ford Bronco, Polaris RZR and CanAm X3. Compared to other aftermarket shocks, Fox uses higher quality materials, but are considered one of the more expensive options on the market. However, with price comes quality and you “get what you pay for”.  In addition to the high quality materials Fox uses, their DSC Adjuster is one of the most advanced shock adjusters on the market. For towing or fine tune adjustments, the DSC Adjusters are a great feature to have. Fox Performance Elite Series shocks come standard with DSC adjusters and aluminum bodies which will help avoid corrosion.

Here at AccuTune Offroad, our Engineers spent several weeks testing and tuning the Fox shocks in order to get the best possible comfort and performance out of them. Our standard tuning (no upgrade kit) improves comfort on road by reducing road feel and helps soak up small bumps. If you’re looking for the ultimate performance with these Fox shocks, we offer an upgrade package that includes better bump stops, pistons and springs. With these upgrades and our custom tuning, you can expect significant improvements in on-road smoothness, more bottom out resistance, and improved bottom out feel. If you love the Fox brand, and want to invest in high quality shocks that perform well, AccuTune Offroad has you covered.

King Shocks is one of the most well known shock brands in the off-road industry. They are Family Owned & Operated – 100% Designed, Manufactured & Assembled in the U.S.A since 1996. Their high performance shocks can be found on top tier race trucks all over the world. King offers a great variety of OEM fit high performance shocks at a reasonable price. These shocks look great, can be tuned, rebuilt and upgraded to fit your needs. King carries over most of their race parts to their OEM line so your daily driver can have a touch of trophy truck technology. For these Bronco shocks, King has done a great job providing the full package you expect. These King Coilovers come with proper spring rates, rear shock shaft guards and come standard with finned reservoirs that look great. The iconic King anodized blue aluminum components definitely stand out and look amazing.

When it came time for tuning the King Shocks, we jumped right into changing the valving in all the shocks and replacing the piston in the rear shocks. After quite a few valving changes, we were able to make big improvements to on-road comfort and performance. With our final valving changes in place, we experienced a much smoother ride on the highway with less vibrations. The new valving in the shocks allowed us to drive faster and more controlled through bigger bumps without bottoming out. One issue we encountered while installing the front King Shocks were the CV joints binding when the shocks were fully extended (the CV joints actually broke on our test vehicle). Unfortunately the CV joints binding on the front axles were due to the shock lengths being too long. To prevent this from happening, we offer CV savers that we can install inside the shocks. If you want the coolest off-road shocks that perform as good as they look, AccuTune Offroad has the King shock package for you.

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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 |

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