Servicing the “non-servicable” OneUp Dropper Cartridge

Introduction: Servicing the “non-servicable” OneUp Dropper Cartridge

If you have a few OneUp Droppers like myself, it’s possible you’ve had issues with the non-serviceable cartridges. OneUp are extremely good with their warranty and usually replace the cartridges if they’ve failed during the warranty period, also the replacements are relatively cheap. But if you’re in a pinch and desperately need to service your cartridge then this Instructable shows you how to do that.


  1. 3d printed tool to remove base of cartridge (or can be made out of 3mm plate)
  2. Four old threaded 2mm spokes
  3. 8mm spanner
  4. Syringe
  5. Light Grease
  6. Bike Specific Suspension/Damper Fluid (about 60mL)
  7. 4mm hex tool
  8. Soft Jawed Clamp

Step 1: Remove the Cartridge

Follow OneUps instructions to remove the cartridge.

It's really easy and everything is on their website.

Step 2: Depressurise Cartridge

Remove the pressure from the cartridge by releasing it from the Schrader valve

Step 3: Assemble Your 3D Printed Tool

  1. 3d print the tool, it’s a 9mm hole in the center with 2mm holes spaced 10mm apart in a square pattern (Spokes are 2.5mm x 1mm thread pitch, so if you are making this out of steel you will need a tap about that size)
  2. Assemble your 3d printed tool
  3. Cut the J-bend ends off the spokes
  4. Using a drill, sand the threaded ends to a tip
  5. Using a drill, thread the spokes into the 3d printed tool

Step 4: Remove Bottom of Cartridge

Remove bottom of cartridge off with the 3d printed tool

Drain fluid into a container

Step 5: Remove Top of Cartridge

Remove top of cartridge using a 8mm spanner

Step 6: Inspect All Parts

Pull plunger from cartridge and clean everything with isopropanol

Inspect all parts

My dropper had a broken spring and gasket. I used a soft jawed clamp to hold the shaft and removed the end with a 4mm hex tool and removed the tip to replace them. The spring was 5mm Diameter x 8mm length and the gasket was 3/16” ID with a 1/16” thickness.

Step 7: ​Assembly

Grease the air valve gasket and insert into cartridge and tighten

Step 8: Fill With Fluid

Completely fill the inner chamber with 25ml of suspension fluid. Place a small amount (Maybe 20ml) of fluid in the outer chamber.

Insert the piston slightly, fill any space in the inner chamber after inserting the piston.

Step 9: Install Plunger and Cartridge Bottom

Grease and install the bottom of the cartridge using the 3d printed tool. Some fluid may escape, that is okay.

Test the cartridge. Pump to 250PSI and compress the cartridge as far as it will go, if it's too hard to compress fully or stops (hydraulic lock) then you will need to let some fluid out of the outer chamber only. You can do this by turning the cartridge up-side-down and releasing the air valve.

Do not do the test with the shock pump attached. The additional air volume will make it easier to to compress the cartridge and performance will change drastically when you take the shock pump off. You may also damage your shock pump if it not rated for around 600-700PSI as the pressure will increase when you compress the cartridge.

At no point, operate the cartridge whilst it is on it's side or up-side-down. If you do you will suck air into the inner chamber and need to redo the fluid filling process again.

Step 10: Assemble Dropper

Follow OneUps instructions on reassembling the dropper.

Do not operate the cartridge when it is upside-down or on it's side, you'll force air into the wrong side of the piston and it will become squishy. If you have done that you will need to start the steps over again.

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