Introduction: Pumping Up a 2013-2015 FOX FLOAT CTD Boost Valve Shock Damper After a Rebuild

This tutorial is for pumping up a 2013-2015 FOX FLOAT CTD Boost Valve Shock Damper after a rebuild. It describes how to make the tools needed to charge the IFP Chamber.

This is a proper service, not a half measure like the Schrader valve mod.

Note that I substituted nitrogen for air. This will reduce shock performance slightly. If shock performance is important to you then use nitrogen instead.

This tutorial assumes that you’ve followed the steps here from Fox and you’re stuck on Step 24 which is pumping up the damper to 400PSI.


  • Do Your Own Research (DYOR) before attempting any of this!
  • Be aware that this tutorial uses 400PSI. Just take a few minutes to think about that, 400 Pounds Per Square Inch. For every square inch there is the equivalent of 400 pounds of weight waiting to escape and hurt you.
  • Never underestimate stored pressure, use safety glasses, use gloves, and consider using a face shield.
  • Do not put yourself in the line of fire, ever


  • A full set of standard hand tools, pliers, side
    cutters, needle nose pliers, hacksaw, drill, drill bits, g-clamp.
  • 100 pack of Hypodermic Needles – Trust me, these are cheap and you’ll want lots of spares. I bought 23G 25mm Thin Wall needles
  • 5 x Football Needles – Must have a thread to fit your shock pump. You’ll want more than one
  • 1 Tube of RTV Silicone – I used Permatex® Ultra Blue® Multipurpose RTV Silicone Gasket Maker however any gasket maker will do
  • Toothpicks
  • 1 x Shock Pump capable of going to 400PSI – I’d get one rated for 600PSI, it’ll be easier to use than a standard shock pump
  • Leather Punch (6mm and 8mm)
  • Razor Blade or Box Cutter
  • Some Rubber about 3-4mm thick – I used a spare PVC Pipe Flex Coupling from a hardware store, but any plain rubber will do
  • 4mm Hex Key – To be destroyed, the worse quality the better as you want soft metal so you can drill through it easy
  • 3mm Metal Sheet (small)
  • A wood screw

Step 1: Make the Air Fitting

  1. Get the football needle, cut the needle part off with some side cutters and open the hole back up because it will be squashed after cutting.
  2. Discard the needle portion and keep the threaded portion of the football needle.
  3. Grab a hypodermic needle, thread the hypodermic needle though the hole in the football needle.
  4. Measure and cut the hypodermic needle flush with the top of the football needle. If you use side cutters, ensure you haven’t squashed the small hole in middle of the hypodermic needle. I put the pointy end into my mouth blew, I could still feel the air coming out of the good ones.
  5. Get the RTV Silicone, squeeze a pea sized portion out on a piece of paper.
  6. Using the tooth pick, pack the silicone into the threaded part of the football needle between the hypodermic needle (to seal it).
  7. Pull the hypodermic fully into the football needle.
  8. Using another toothpick, smooth the RTV silicone so that it is level with the top of the football needle, make sure all holes are filled and take care not to block the hypodermic needle.
  9. Leave to cure for 24hours or more. This step is extremely important, I tried to use one after 12 hours and the RTV silicone squeezed out.

Step 2: Making Extra Rubber Pellets

    1. Get your leather punches and rubber
    2. With a hammer and the punch, punch out a few circles out of the rubber using 6mm and 8mm punches. I ended up using the 6mm pellets, they are a bit small but fit really easily.

    Step 3: Making the Hollow Hex Tool

      1. Grab a 4mm hex tool
      2. Using a 1.5mm drill bit, drill into the hex tool directly in the center about 15mm
      3. Grind or cut the hollowed out hex tool to a length of about 10mm.
      4. Put this tool aside
      5. Grab the 3mm metal sheet
      6. Grind or cut a small piece about 50mm x 15mm
      7. Grind or cut a slot about 4mm wide. Test regularly if it fits the 4mm hex tool, it needs to be tightly fitting. If it’s too loose it’ll strip.

      Step 4: Depressurising the Damper (Tips in Addition to FOX’s Instructions)

      Warning: This is ONLY for the 2013-2015 FOX FLOAT CTD Boost Valve Shock. If you have a shock with high/low speed compression (the little additional smaller cylinder on some shocks like Float X or X2’s), the bleed for the fluid is challenging, you will need a vacuum pump capable of drawing a decent vacuum and the whole process is out of the scope of this tutorial. In addition, these shocks are filled with damper fluid from the bottom hole, there is another hole on the smaller cylinder that is used to charge the damper.


        1. Drill a 1.5mm hole about 3mm deep into the white deralin ball
        2. Using a wood screw, screw it into the hole and pull out the deralin ball.
        3. Using a 4mm hex tool, undo the bolt a couple of turns. Warning: Under no circumstances remove the bolt or undo more than a couple of threads! It could be still under pressure
        4. Using a hypodermic needle, pierce the rubber slug through the bolt. The pressurized air should escape. If it doesn’t stop and assess the situation carefully before making any decisions, there is about 30-40kg of force on the 4mm bolt (due to the size of the hole) due to the internal pressure of the damper
        5. If you’ve successfully released the air, remove the needle and remove the bolt
        6. The rubber pellet is really hard to get out, I’d recommend leaving it in there at this stage unless you have a fish hook handy. When you’ve opened the damper push the IFP down really quickly and it should eject the rubber pellet.

        Step 5: Servicing the Damper (Tips in Addition to FOX’s Instructions)

          1. I’d recommend only removing the body bearing, don’t remove the propedal or the shim stack as there’s a heap of tiny breakable parts in there. If you are confident you can handle it and have the tools then go for it, but I just changed the damper fluid.
          2. I recommend using a large syringe to suck up the new damper fluid, then block the end and pull the plunger. This will draw a vacuum on the liquid and expand the air trapped in it. Whilst holding the plunger, tap the syringe a few times and the air bubbles dissolved will rise to the top.
          3. There’s a really good chance if your shock is noisy, it’s probably just lose IFP chamber pressure. You could skip all the steps and just pump up the IFP chamber again and it could be as good as new. The IFP chamber pressure is only held in by the rubber pellet.

          Step 6: Refilling the IFP Chamber

            1. Grab your hypodermic needle tool and connect it to the shock pump taking care not the snap or bend the needle. I used some needle nose pliers to tighten the hypodermic needle tool into the shock pump
            2. Thread it though the hollow hex key.
            3. Slip over the retaining bolt
            4. Grab a new rubber pellet, and pierce the rubber with the needle
            5. Grease the rubber taking care not the block the needle end. Any grease will do, I used Maxima Waterproof grease.
            6. Check you can still pump air through the needle
            7. Using your custom 4mm tool, screw in the retaining bolt taking care not the bend or dislodge the needle
            8. Tighten the retaining bolt.
            9. Pump up the IFP Chamber to at least 400PSI but no more than 500PSI
            10. Remove the needle from the shock quickly
            11. Tighten the retaining bolt using an allen key