2013-2015 FLOAT CTD Boost Valve Rebuild
- 398-00-280 Tooling: Eyelet Torque Tool
- 803-00-805 Kit: Shaft Clamps, Shocks, CTD 9mm, 3/8in, 1/2in, 5/8in
- Nitrogen Fill Station (Tank with Regulator) required for full rebuild .
This service procedure guides you through the rebuild of a FLOAT CTD Boost Valve rear shock. For additional information and complete assembly drawings please visit FLOAT CTD Boost Valve »
Some pictures used below show different models of shocks, but all procedural information is the same. Please use this service procedure for information regarding all FLOAT CTD Boost Valve shocks.
WARNING: FOX products should be serviced by a qualified 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: 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.
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 insturctions and warnings in that instance.
WARNING: Never attempt to pull apart, open, disassemble, or service a FOX shock that is in a "stuck down" condition. A "stuck down" condition results from a failure of the dynamic air seal (located between the positive and negative air chambers within the shock air sleeve), resulting with the negative chamber retaining a higher pressure than the positive chamber. To test whether the shock is in fact "stuck down":
- Remove the air cap and depress the Schrader valve, to completely release air pressure from the positive chamber of the shock.
- If your shock has an EVOL air sleeve, you must release air pressure slowly to stop from inducing a "stuck down" condition.
- If the shock body retracts into the air sleeve near bottom-out after the air is slowly released from the positive chamber, attach a FOX high pressure pump and pressurize the shock to 250 psi/ 17 bar).
- If your shock has an EVOL air sleeve, you must cycle the shock after every 50psi addition while filling.
- If the shock does not fully extend, it is in a "stuck down" condition.
WARNING: Any improper servicing procedure with FOX air shocks in the "stuck down" condition can lead to SERIOUS INJURY OR DEATH. Contact FOX or an Authorized Service Center for repair.
Using a pick tool, remove the nylon plug to access the pellet screw. Use a 5/32" hex to release the nitrogen pressure and remove the pellet retaining screw. Remove the pellet with the pick tool.
Clamp the shock vertically and use a 5/64" hex to remove the bleed screw. As you first crack the bleed screw, pay attention to the oil quality as it leaks out; foaming indicates aerated oil.
Remove the shock from the vice and while inverting it over a clean towel, tap out the bleed screw ball. This can also be accomplished by compressing the shock slightly. Be very careful with this, as oil and the ball bearing may shoot out.
Remove the IFP using carefully applied air pressure. Inspect the body for damage or excessive wear.
Remove the IFP o-ring and inspect its gland on the piston itself for any damage or contamination. Apply Slick Honey grease to the new IFP o-ring from the replacement seal kit, and install it on the piston.
Set the IFP to the proper depth for your shock size.
|5.500 x 1.000||1.450in.|
|6.000 x 1.250||1.670in.|
|6.500 x 1.500||1.880in.|
|7.250 x 1.750||2.100in.|
|7.500 x 2.000||2.310in.|
|7.875 x 2.000||2.310in.|
|7.875 x 2.250||2.500in.|
|8.500 x 2.500||2.740in.|
Install a new pellet from the service kit, the flat side facing up, and secure with the pellet screw. Prefill the shock body with oil, pouring down the side to minimize potential aeration of the oil. Set the body aside in a vertical position and move on to the topcap, allowing time for any trapped air to escape.
If you are servicing a FLOAT CTD Boost Valve Remote shock, go to the CTD Remote Eyelet section »
Using a 9 mm wrench, remove the piston nut. Be careful not to lose the 4 x 10 valve shim that can stick to the nut.
Remove the valving assembly and lay it out in assembly sequence on a clean lint-free towel. Carefully inspect the shims for damage or excessive wear.
There are new Inner and Outer Boost Valve parts that can help eliminate BV sealing issues.
Please visit the Technical Service Bulletin to learn about the updated Boost Valve parts: Tsb - SHOCK- Updated Boost Valve Parts for FLOAT Shocks »
Replace all boost valve o-rings and the piston glide ring from the replacement parts kit. Be sure to replace the o-ring that is installed underneath the glide ring.
Some CTD BV shocks have been built with the updated Boost Valve parts. Please visit the Technical Service Bulletin to learn about the updated Boost Valve parts: Tsb - SHOCK- Updated Boost Valve Parts for FLOAT Shocks »
After replacing all seals and any worn or damaged valve shims, reassemble and stage the stack as shown and set it aside for now.
Remove the piston post with a chamfer-less 8 mm socket, followed by the Propedal piston and spring, setting all these parts aside.
Remove the body bearing. Replace the o-rings, quad ring and backup rings from the replacement parts kit, installing with Slick Honey.
Remove the bottom-out bumper and shim, invert the eyelet assembly and clamp it by the shaft using the appropriate shaft clamps.
Apply some heat to the outside of the eyelet to soften the red Loctite®, then remove the eyelet assembly from the shaft.
Inspect the compression/rebound rods and the end of the shaft, for any signs of corrosion or scratches. If either rod is damaged, replace it with a current revision part. Replace the shaft o-ring.
Remove the compression rod and spring, being very careful not to lose the ball on the rod tip. Replace the o-ring inside the rebound rod.
Apply a small amount of Slick Honey to the non-ball end of the compression rod, then slide it back into the rebound rod either end first. Install the rebound assembly spring.
Apply a small amount of Slick Honey to the rebound assembly and install it into the shaft assembly. Apply a small amount of Slick Honey to both ends of the rebound/compression rods, to lubricate the junction point with the CTD compression cam.
Rebound and Compression Knobs and Final Assembly
Using a 1.5 mm hex wrench, remove the set screw from the top of the eyelet assembly, allowing the CTD lever cam assembly to be removed. Do not lose the detent ball and spring for the CTD lever!
Install new eyelet shaft and air sleeve o-rings from the replacement parts kit with Slick Honey. Clean the shaft threads of old Loctite® with alcohol.
Separate the rebound cam from the compression cam, inspecting for any signs of corrosion or damage. Reassemble these two parts after thoroughly cleaning and lubricating, making sure the rebound cam can spin freely within the cam assembly. Set the rebound cam/compression cam aside for now, to continue servicing the CTD lever assembly.
Thoroughly clean all parts, inspecting for damage or wear. During reassembly, be sure to set the point on the black knob into the middle slot of the blue lever.
Reassemble the CTD compression lever assembly, as shown. Be sure the retaining ring is fully seated into its groove.
Set the CTD knob detent spring and ball into the eyelet with some grease to hold in place as you install the control knob assembly.
Install the set screw with a 1.5 mm hex wrench until lightly seated, then back it out a quarter turn. Make sure the lever assembly can move freely and smoothly.
Apply red Loctite® to the eyelet shaft threads. Given the particular shock you are working on and per the graphic diagrams below, as you thread the shaft into the eyelet assembly, be sure the rebound and compression rods are correctly oriented with the rebound and compression cams.
After cleaning the clamps and shaft with alcohol, clamp the shaft just enough to secure but not damage it. Tighten the eyelet assembly onto the shaft to 80 in-lb torque.
Lightly install the bleed screw into the body bearing without the bleed screw ball, to plug the bleed hole. Install the body bearing onto the shaft, coating the shaft o-ring with Slick Honey.
Install the Propedal check valve and spring, then coat with red oil. Install the piston post over the Propedal check valve and coat with red oil.
Install the pre-assembled valve stack, tightening the piston nut finger tight. As you press the Propedal piston check valve down with a 2 mm hex wrench, pre-fill the piston bolt area with red oil. This action helps to allow oil to flow below the valve stack.
Tighten the valve stack piston nut into the piston bolt to 60 in-lb torque; both the piston nut and bolt simultaneously tighten to the same torque. Continue with pre-filling the piston area, to further evacuate any trapped air.
With the oil-filled body in one hand and the eyelet assembly in the other, join the two in one swift movement.
Holding the combined parts together in one hand, remove the bleed screw. Keeping the bleed hole at the high point, hand-tighten the body into the body cap from below, watching for air bubbles escaping the bleed hole. As you thread the two parts together, tap the body to help any trapped air to escape.
Clamp the shock by the body eyelet. Tighten the body cap onto the body, remembering not to apply wrenching force directly on the flat side directly adjacent to the bleed hole.
Pressurize the IFP chamber of your shock in accordance with the boost valve tune on the air sleeve decal. After pressurizing, dyno-test the shock.