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Home > Technical Info > Technical Articles > Fox Vs. King

Fox Vs. King

Fox Shocks vs. King Shocks

Off Road Engineering is proud to bring you a comparison of the two top off road racing shocks on the market today.

          

As we continue to receive questions regarding the differences between the two major shock brands of today's off road racing market, we've decided a comparison must be done to put the opinions in perspective. Here is what Fox, King, and Off Road Engineering had to say about Fox's Pro Series 2.5" Coil Over Shocks, and King's Prerunner Series 2.5" Coil Over Shocks.

                          

Technical Specifications

Disassembly of both brands was relatively straightforward. The tools necessary were: Crescent Wrench, Shock End Cap Spanner, Small Flathead Screw Driver, Large Internal Snap Ring Pliers, Small Allen Wrench, and a Rubber Mallet.  
FOX: The bearing assembly body is made of 6061 aluminum. The Slit in the side of the bearing assembly made purging the air out of the shock easy. The seals are made of Buna. The internal bearing is made of bronze with a teflon coating. Retails for $35 complete w/seals. (Part # 812-07-002-a) or $20 w/o seals (Part# 203-00-003-b) KING: The bearing assembly is made of 6061 aluminum. The aluminum washer on top of the main seal of  Kings Bearing Assembly retains the main seal. King's Shock seals are made of Buna. The internal bearing or guide bushing is made of bronze with a teflon coating.
FOX: The Spring Divider from Fox is made from injection molded glass impregnated nylon and Retails for $15. (Part # 234-00-035-a) KING: The Spring Divider or Floater is made out of either urethane, injection molded glass impregnated nylon or billet aluminum, depending on what you order from KING. The polyurethane divider retails for $15 The nylon divider retails for $15 and the aluminum floater retails for $50 The spring divider pictured is nylon and significantly thicker.
FOX: The dust cap is made of 6061 aluminum anodized blue. The Scraper seal is made of a compound called "Buna". KING: The dust cap is made of 6061 aluminum, and the scraper seal is made of a compound called "Buna"..
FOX: The Snap Ring from Fox is one heavy duty unit. These are made of steel and gold zinc plated. Retail is $2 (Part #038-00-008-a) KING: These are standard snap rings made of spring steel.
FOX: While this type of lower spring seat involves more parts, it allows maximum coil spring length to be utilized. The spring seat is made of 6061 aluminum and anodized blue. The retaining clips are made of steel. The spring seat retails for $25 (Part# 234-00-032-a). The retaining clips retail for $9ea (Part# 234-00-031-a) The o-ring retails for $1 (Part# 029-00-031-a) KING: These lower spring seats are of solid design. They install by slipping over the shaft and lower eyelet, and are made of 6061 aluminum. One drawback of this design is reduced usable shock travel. Shown is the 2" raised lower spring seat. Retails for $30
FOX: The IFP (Internal Floating Piston) from Fox is substantially lighter than King's. This reduces the momentum of the oil as it plunges in and out of the reservoir. The wear band is made of teflon. The IFP retails for $20 w/o-ring (Part# 805-00-001-a) or $18 w/o o-ring (Part# 223-00-005-b) The wear band retails for $3.50 (Part# 002-00-005-b) KING: The wear band is made of hard teflon and the Floating piston is made of 6061 aluminum. The solid aluminum floating piston is heavy, but additional machining translates to additional price.
FOX: The working piston is made from hard anodized 6061 aluminum and the wear band is made of a hard plastic called "PEET" The piston's overall diameter was measured at 2.268". The wear band's height was measured at .37" KING: The working piston is made from 6061 aluminum and the wear band is made from a teflon bronze composite. The pistons overall diameter was measured at 2.379" the wear bands height was measured at .5"

FOX: The compression side of the working piston has four ports covered by seven shims varying in thickness based on the shock's valving. The ports are ovalized as well as conically bored. The minimum flow area we measured is .844 in.

 

The rebound side of the working piston has four circular ports bored conically. The shim stack consists of six shims of varying thickness based on valving chosen. Each port was measured at .31" in diameter yielding a total flow area of .302 in.

KING: The compression side of the working piston has six ports covered by six shims that vary in thickness based on the shocks valve rate. The diameter of each port is .375" making the minimum flow area .663 in the ports are bored straight.

 

The rebound side of the piston has three ports at .329" diameter each. There are six shims that vary in thickness on the rebound side based on valve stacks used. Total area for flow on the rebound ports is .255 in The ports are bored straight.

FOX: The heim spacers from Fox are made of 4130 chromoly steel. KING: The heim spacers from King are made of 4130 chromoly steel.
FOX: The shaft spacers are machined from 6061 aluminum. KING: The shaft spacer is made of 6061 aluminum tube.
FOX: The reservoir end cap is made of 6061 aluminum and anodized blue. Fox utilizes a special brass schrader valve with an o-ring seal built in. Shock pressures can vary widely depending upon setup. KING: The reservoir end cap is made from 6061 aluminum and anodized blue. The schrader valve uses a standard stainless steel 1/8" NPT thread pitch and seals with teflon tape. Shock pressures can vary widely depending upon setup.
FOX: These valve shims are made of Sandvik 20 steel and then tumbled to remove any sharp edges. The shims can vary in diameter from 2" - .8" and in thickness from .006" - .015". Shim stacks are different from compression to rebound in number and size. Shims sell for $1 ea or slightly less in a stack. They are also available in a kit for $200. KING: The engineering Dept. at King would not disclose the material their shims are made of, but based on our observations we would guess spring steel. Shim stacks utilize six different diameters: 1.75", 1.6", 1.45", 1.3", 1.15", and 1.01". Thickness options are: .008", .010", .012", .015", and .020".  Shims sell for $2.75 ea or $16 per stack.
FOX: These stop washers keep the shock from overextending. The washer is made from stamped steel. KING: These stop washers keep the shock from overextending. The washer is made of stamped steel.
FOX: These washers are designed to be adjustable for the different height and type of shim stacks utilized. Fox uses a lock nut to retain the working piston and shaft assembly components. These are torqued to 35 ft/lbs. KING: The top nut on the shaft is a heavy duty jam nut. Red Locktite is used to keep the nut from backing off. Different height washers are available for purchase from King. Maximum torque is significantly higher.
FOX: The reservoir from Fox has the advantage of more oil capacity and greater surface area for cooling. The ribs also provide extra strength. Fox reservoirs are made from low carbon DOM steel tubing. Length is 14". KING: The reservoir body is made from 6063 drawn aluminum tube. While aluminum radiates heat better we have found that the tube and the floating piston have .005" looser tolerances, thermal expansion slightly exacerbates this. This is the main reason we find small amounts of oil bypassing the floating piston and moving into the nitrogen chamber. Length is 10.75".
FOX: The eyelets from Fox are made of 6061 aluminum and always come with a rubber bump stop. Fox also utilizes FK Rod Ends for their spherical bearings. KING: The eyelets are made from 6061 aluminum with rubber bumpers available upon request. King would not disclose the bearing manufacturer used.
FOX: 17-4 Stainless steel shafts are utilized on all Fox Shocks except for the 1.25" and 1.625" shaft air shocks. The shafts on the 2.5 shock pictured is .875" in diameter. KING: The material used would not be disclosed but we believe the shafts to be made of  steel and hard chrome plated. A nice advantage of King shocks is the chamfered edge where the seal assembly slips over. This makes for easy reassembly without galling the wiper seal.
FOX: A close up of the spring seat retaining clip groove and rubber bumper. KING: An unfortunate effect of damaged chromed steel shafts is rust pitting. If not properly lubricated and protected the rust will continue to corrode the shaft and possibly damage the seals and internal bearing.
FOX: The reservoir lines are made from Aeroquip High Pressure Hose and Steel reusable fittings. The hose is -10 and pressure rated to 1750 psi with 6 layers. All Fox shocks utilize o-ring sealed steel JIC fittings. One drawback of this heavy duty hose is it is less flexible.  KING: The reservoir lines are made from Aeroquip Racing Hose and crimped steel fittings. The hose is -10 and pressure rated to 250 psi with 3 layers. King Shocks use pipe thread with teflon tape to seal their fittings. One drawback of the low pressure hose is the relatively small amount of compression ratio adjustment available.
FOX: The shock body is made from low carbon DOM steel tubing then honed and threaded. Fox top caps are smaller in diameter than the body allowing spring hardware to be removed from the top of the shock. This makes converting to triple rate easier.  We measured the tubing at 2.557" x .120". KING: The shock body is made from low carbon DOM steel tubing then honed and threaded. The top cap must be removed to install or remove coil hardware. This makes triple rate hardware more difficult to install. We measured the tubing at 2.62" x .127".
FOX: Seal kits for this shock retail for $15. KING: Seal kits for this shock retail for $20


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