2019-2024 FIT4 F-S/P-Se 3Pos w/Adj Damper Cartridge Rebuild
Required Parts
- 025-03-023 Oil: Suspension Fluid, 5wt, Teflon Infused, 1.0 US Quart
- 025-03-072 Oil: AM, FOX 20 WT Gold, T22238, 32 oz
- 803-01-323 Seal Kit: MY19+ 32/34 SC 8mm shaft FIT4 Cartridge Rebuild
- 803-01-431 Seal Kit: MY20+ ALL 32/34 Non-SC 8mm Shaft FIT4 Cartridge Rebuild
- 803-01-432 Seal Kit: MY20+ ALL 36 8mm Shaft FIT4 Cartridge Rebuild
- 803-01-549 Seal Kit: MY21+ ALL 38 8mm Shaft FIT4 Cartridge Rebuild
Required Tools
- 398-00-320 Tool: 8mm Shaft Bullet, 32 FIT Cartridge
- 398-00-681 32 Damper-side and ALL 32-34-36-38-40 Spring-side Removal Tool
- 398-00-682 34-36-38-40 Damper-side Removal Tool
- 398-00-702 Tooling: Fork Topcap Socket, 26mm, 3/8 Drive
- 398-00-918 Tooling: 2022 TC Fork Air-Damper Nut Torque Tool (Only Needed for 32 Taper-Cast)
- 803-00-147 Kit: Shaft Clamps, 07 FORX, Set #2 (32 X Body, 36, 40 Forx)
- 803-00-276 Service Kit: Hand Bleed, Syringe and Tube, 2010 32 Fit RL-RLC Cartridge
- 820-09-084-KIT Service Tooling: 2022 TC Fork Air-Damper Shaft Removal Assembly KIT (Only Needed for 32 Taper-Cast)
Supplies Needed
- 10mm Socket
- 11mm Crow's Foot
- 11mm Wrench
- 12mm Crow's Foot
- 12mm Wrench
- 15mm Socket
- 19mm Crow's Foot
- 19mm Wrench
- 2.5mm Hex Wrench
- 2mm Hex Wrench
- 6mm Hex Wrench
- Magnet
- Mallet
- Park Tool FR-5 or FR-5.2 (Only needed for 32 Taper-Cast)
- Propane Torch
- Ratchet
- Red Loctite 263
- Seal Pick
- Torque Wrench
- Ultraplex LT2 or Stay Lube SL3125 Blue waterproof grease
- Waste Oil Basin
WARNING: Always wear safety glasses and protective gloves during service to prevent potential injury. Failure to wear protective equipment during service may lead to SERIOUS INJURY OR DEATH.
WARNING: FOX products should be serviced by a trained bicycle service technician, in accordance with FOX specifications. If you have any doubt whether or not you can properly service your FOX product, then DO NOT attempt it. Improperly serviced products can fail, causing the rider to lose control resulting in SERIOUS INJURY OR DEATH.
WARNING: FOX suspension products contain pressurized nitrogen, air, oil, or all 3. Suspension misuse can cause property damage, SERIOUS INJURY OR DEATH. DO NOT puncture, incinerate or crush any portion of a FOX suspension product. DO NOT attempt to disassemble any portion of a FOX suspension product, unless expressly instructed to do so by the applicable FOX technical documentation, and then ONLY while strictly adhering to all FOX instructions and warnings in that instance.
WARNING: Modification, improper service, or use of aftermarket replacement parts with FOX forks and shocks may cause the product to malfunction, resulting in SERIOUS INJURY OR DEATH. DO NOT modify any part of a fork or shock, including the fork brace (lower leg cross brace), crown, steerer, upper and lower leg tubes, or internal parts, except as instructed herein. Any unauthorized modification may void the warranty, and may cause failure or the fork or shock, resulting in SERIOUS INJURY OR DEATH.
NOTE: The Factory and Performance Elite FIT4 damper can be found in a number of different fork chassis options. Images for this procedure were shot using various damper cartridges. Some images of the damper in this procedure may appear different than yours. Please follow the procedure below for a complete damper rebuild.
Removal From Fork Chassis
Step 1
Hold the black Open Mode Adjust knob from turning while you unthread the set screw counter-clockwise with a 2.5mm hex.
NOTE: Compression Adjust knobs may be Black, Blue, or Orange.
Step 2
Remove the 2.5mm hex screw followed by the Open Mode Adjust knob and the Compression Selector knob.
Step 3
Regardless of fork configuration, use a 2mm hex wrench to turn the set screw counter-clockwise. Remove the knob and set it aside.
Step 4
Use a 10mm or 15mm socket (depending on fork chassis) to unthread the bottom nut counter-clockwise. Remove the bottom nut and crushwasher. Discard the original crush washer that may be stuck to the bottom nut.
For 32 Taper-Cast: Use the TC Nut Torque Tool (PN: 398-00-918) to unthread the bottom nut counter-clockwise. Take care not to damage the painted finish on the lower leg when using the TC Nut Torque Tool.
Step 5
Use Damper Removal Tool 398-00-681 or 398-00-682 depending on fork chassis to dislodge the shaft from the lowers. Make sure that you have approximately half of the available threads engaged with your tool before striking with your mallet. Remove the damper removal tool, then bring the fork upright over an oil basin to drain.
Step 6
FOR 32 Taper-Cast: Install the dummy Bottom Nut that comes with the TC Damper Removal Tool Assembly (PN: 820-09-084-KIT) onto the bottom stud threads with it's larger diameter end toward the fork. Make sure to engage approximately half of the available threads with your tool. Place the Bottom Nut Plate of the removal tool onto the dummy Bottom Nut. Carefully hit the upper Strike Plate with your mallet to dislodge the Rebound Adjuster from the lower leg. Remove the dummy Bottom Nut then bring the fork upright over your waste oil basin.
Step 7
Use a chamfer-less 6-point 26mm (PN: 398-00-702) or for 32 Taper-Cast forks use the Park Tool FR-5 or FR-5.2 Cassette tool to unthread the damper topcap by turning it counter-clockwise. Pull up to remove the damper from the fork chassis.
Damper Topcap and Bladder Assembly Rebuild
Step 1
Clean the cartridge body with isopropyl alcohol and a lint-free paper towel, then clamp it in your shaft clamps (PN: 803-00-147).
Step 2
Use a small pick in the hole of the Compression selector to remove the wire ring retaining the Compression Adjust Coupler. Thread the knob retaining screw back into the coupler then pull up to remove it. Be careful and retain the detent ball and spring present in the coupler when removing. Replace the o-ring on the coupler with a new greased one from the kit.
Step 3
With the cartridge still vertical in your shaft clamps, use a 19mm wrench or crow's foot to loosen the sealhead from the body by turning it counter-clockwise when viewed from below.
Step 4
Remove the damper from your shaft clamps, then continue to unthread the sealhead from the cartridge body over your waist oil basin. Drain all oil out of the damper. Squeezing the bladder may help expel additional oil.
Step 5
Invert the bladder assembly so the topcap is on the bottom. Then remove the retaining ring from the bladder ring. Remove the bladder retainer then slide the bladder ring down slightly onto the bladder.
Step 6
Clamp the cartridge body in your shaft clamps, then turn the topcap counter-clockwise with your 26mm 6-point chamfer-less socket or Park Cassette tool for 32 Taper-Cast forks (shown).
Step 7
In some cases the compression piston clamp will separate from the body while still threaded into the topcap body, use an 6mm hex wrench in through the bottom of the compression clamp and your topcap socket or cassette tool (for 32 Taper-Cast) to unthread the topcap from the compression piston clamp.
Step 8
Remove the compression valving and compression piston clamp by unthreading them from the body counter-clockwise with an 8mm hex wrench.
Step 9
Remove the check valve, spring, and plate from the top end of the cartridge body. Separate the cartridge body from the bladder. Discard the bladder.
Step 10
Remove the compression piston and internal topcap parts from the topcap. Inspect valving and replace any damaged parts. Clean the inside of the topcap with Isopropyl alcohol and dry with a lint-free paper towel.
Step 11
Reinstall the lockout selector with compression adjust needle into the compression selector. It can only go in one orientation and must seat fully. Reinstall the butterfly valve onto the lockout selector making sure the holes in the butterfly valve align with the appropriate sized posts on the lockout selector.
Step 12
Note the ball bearing bearing present in the side of the compression piston. Align the ball in the piston with the groove in the topcap wall. Reinstall the piston into the topcap with the flat side of the piston oriented toward the top of the topcap.
Step 13
Verify the correct orientation of the valve stack. Reinstall the valve stack into the topcap making sure to center the shims on the raised portion of the compression piston.
Step 14
Prepare the new bladder by installing the bladder ring with it's larger diameter end oriented toward the small end of the bladder.
Step 15
Reinstall the Compression Piston Clamp into the large end of the bladder making sure to seat the lip of the bladder into the groove of the Compression Piston Clamp. Reinstall the prepared bladder assembly into the topcap by threading the compression piston clamp into the topcap clockwise with an 8mm hex wrench. This will be tightened later.
Step 16
Reinstall the check plate, check spring (with larger end first), then the check shim into the internally threaded end of the body. Reinstall the body into the bladder with the internally threaded end first. Thread the body clockwise onto the compression piston clamp.
Step 17
Carefully clamp the body in your shaft clamps, making sure to only clamp on a smooth section of the body. Tighten the topcap clockwise using your 6-point chamfer-less socket or cassette tool (32 Taper-Cast) to 55 in-lb (6.2 Nm) torque.
Step 18
Reinstall the bladder retainer followed by the retaining ring. Make sure that the retaining ring is fully seated in the bladder ring.
Step 19
Remove the detent ball and spring from the Compression Adjust Coupler. Reinstall the Compression Adjust Coupler into the Compression Selector making sure to push down to seat it fully.
Step 20
Invert the Topcap Assembly and support it with your topcap socket or cassette tool (32 Taper-Cast). Slowly fill the cartridge body with FOX 5wt. Teflon infused oil (PN: 025-03-023). Squeeze the bladder then hold it compressed until escaping air bubbles reach the surface of the oil in the body. Then release your squeeze and add more oil until repeated cycles of squeezing, waiting, and refilling leave the body full and no air bubbles are present. Top off the body with oil and set aside.
Step-Cast and Taper-Cast Damper Shaft Assembly Rebuild
Step 1
Clean the damper shaft with Isopropyl alcohol and a lint-free paper towel. Carefully clamp the shaft in your 8mm shaft clamps. Remove the rebound detent set screw by turning it counter-clockwise with a 2mm hex wrench. Remove the detent ball and spring.
Step 2
Remove the o-ring on the outside of the Rebound Adjuster. Carefully heat the rebound adjuster for 3-5 seconds with a propane torch to break down the Loctite. Be careful as these parts will be hot. Unthread the Rebound Adjuster from the shaft by turning it counter-clockwise with an 11mm wrench.
Step 3
Remove the Rebound Adjuster from the Rebound Adjuster Body by unthreading it counter-clockwise. Replace the o-ring within the Rebound Adjuster Body with a new greased one from the kit.
Step 4
Coat the threads of the Rebound Adjuster with a thin layer of Ultraplex LT2 or Stay Lube SL3125 Blue waterproof grease. Reinstall the Rebound Adjuster into the small end of the Rebound Adjuster Body by theading it in clockwise until it bottoms out. Set the Rebound Adjuster aside.
Step 5
Remove the Rebound Tube from within the shaft. Remove the Sealhead from the shaft by pulling it up. Install the 8mm bullet tool (PN: 398-00-320) into the shaft then coat with a thin film of Slick Honey. Install the new Sealhead from the kit onto the shaft so the wiper is oriented toward the Rebound Adjuster end of the shaft.
Step 6
Remove the bullet tool then reinstall the Rebound Tube making sure it is fully seated within the shaft. Reinstall the Rebound Adjuster. Clean the Loctite residue from the Adjuster threads, then apply 1 drop of red Loctite 263. Thread the Rebound Adjuster clockwise onto the shaft to 30 in-lb (3.4 Nm) torque with an 11mm crow's foot.
Step 7
Install a new greased o-ring from the kit onto the outside of the Rebound Adjuster. Reinstall the detent ball followed by the detent spring into the Rebound Adjuster. Tighten the 2mm set screw clockwise until flush with the Rebound Adjuster Body.
Non-Step-Cast Damper Shaft Assembly Rebuild
Step 1
Clean the damper shaft with Isopropyl alcohol and a lint-free paper towel. Carefully clamp the shaft in your 8mm shaft clamps. Remove the o-ring on the outside of the Rebound Adjuster. Carefully heat the rebound adjuster for 3-5 seconds with a propane torch to break down the Loctite. Be careful as these parts will be hot.
Step 2
Unthread the Base Stud from the Shaft by turning it counter-clockwise with a 12mm wrench or Knipex smooth-jawed parallel pliers. Remove the Base Stud with Rebound Needle.
Step 3
Remove the Sealhead from the shaft by pulling it up. Install the 8mm bullet tool (PN: 398-00-320) into the shaft then coat with a thin film of Slick Honey. Install the new Sealhead from the kit onto the shaft so the wiper is oriented toward the Rebound Adjuster end of the shaft. Remove the bullet tool.
Step 4
Unthread the Rebound Needle counter-clockwise from the Base Stud. Replace the o-ring within the Base Stud with a new greased one from the kit.
Step 5
Remove the detent ball and spring with a magnet to properly position them for Rebound Needle reinstallation. Reinsert the detent spring, followed by the detent ball. Make sure these sit in the bottom of the blind detent hole in the Base Stud.
Step 6
Replace the o-ring on the Rebound Needle with a new greased one from the kit. Coat the threads of the Rebound Adjuster with a thin layer of Ultraplex LT2 or Stay Lube SL3125 Blue waterproof grease. Reinstall the Rebound Needle into the small end of the Base Stud by threading it in clockwise until it bottoms out.
Step 7
Clean the Loctite residue from the Base Stud threads, then apply 1 drop of red Loctite 263. Thread the Base Stud clockwise onto the shaft to 30 in-lb (3.4 Nm) torque with an 12mm crow's foot.
Damper Reassembly and Bleeding
Step 1
Verify that no bubbles are present in the Topcap Assembly, then top it off with FOX 5wt. Teflon infused oil. Slide the Sealhead on the Damper Shaft Assembly all the way to the Rebound Piston end of the shaft. Hold the Compression Adjust Coupler in the topcap. Quickly insert the Damper Shaft Assembly into the Topcap and Bladder Assembly while threading the Sealhead clockwise onto the Cartridge body.
Step 2
Carefully clamp the Cartridge Body in your shaft clamps. Tighten the Sealhead onto the Cartridge Body by turning it counter-clockwise (when viewed from above) with a 19mm crow's foot to 55 in-lb (6.2 Nm) torque.
Step 3
Remove the Compression Adjust Coupler and install the bleed syringe (PN: 803-00-276) into the Compression Selector. Make sure to make a good seal between the syringe and the Compression Selector to prevent air ingress during bleeding.
Step 4
Pour a small volume of FOX 5wt. Teflon infused oil into the open syringe. Squeeze the bladder and hold it compressed. Cycle the shaft to full bottom out, then wait until all bubbles found in the syringe have reached the top of the oil. Slowly release your squeeze on the bladder and add oil if needed to prevent air ingestion into the cartridge. Cycle the shaft down to full extention slowly, adding fluid as needed to prevent air ingestion into the cartridge. Repeat this process until no new bubbles are found in the syringe when squeezing the bladder and cycling the shaft to bottom out. Fully extend the cartridge.
Step 5
With the cartridge fully extended, remove the bleed syringe. Make sure that the Compression Selector is fully topped-off with oil. Reinstall the Detent Spring into the Compression Coupler followed by the Detent Ball. Push the Detent Ball in against the spring while you insert the Coupler into the Compression Selector. Push the Compression Coupler fully into the Compression Selector.
Step 6
Remove the knob fixing screw from the Compression Coupler. Reinstall the wire retaining ring. Reinstall the screw then make sure the retaining ring is fully seated by pulling up on the Compresion Coupler.
Reinstallation Into Fork Chassis
Step 1
Reinstall the rebuilt damper cartridge into the fork chassis. Tighten the topcap clockwise to 220 in-lb (24.8 Nm) torque with your 6-point chamfer-less topcap socket or Park Cassette tool FR-5 or FR-5.2 (32 Taper-Cast).
Step 2
Inject the appropriate amount of FOX 20wt. Gold oil (025-03-072) into the lower leg damper-side bath.
Bath oil volumes can be found here»
Step 3
Install a new crush washer into the damper side bottom nut (use a small amount of Slick Honey to retain the crush washer during installation). Install the bottom nut, tighten 10mm bottom nuts to 50 in-lb (5.7 Nm). Tighten 15mm bottom nuts to 80 in-lb (9.0 Nm).
FOR 32 Taper-Cast: Use the TC Nut Torque tool to tighten the bottom nut clockwise to 50 in-lb (5.7 Nm) torque. Make sure to orient your TC Nut Torque tool 90 degrees from the handle of your torque wrench to acheive accurate torque values.
Step 4
FOR NON-Step-Cast: Use a 2mm hex wrench to reinstall the red rebound knob. Make sure that the set screw lines up with the depression in the rebound adjuster shaft.
FOR Step-Cast: Engage the hex of the Rebound knob with the hex feature on the Rebound Adjuster. Tighten the 2mm set screw clockwise to 5 in-lb (0.56 Nm) torque.