HOW TO SERVICE A ONEUP DROPPER SEATPOST

Use a wrap of electrical tape to mark the height of the post in the frame, then pull the post out and unclip the cable from its base. Mark the position of the saddle rails in the clamp, then remove the rear bolt and take off the saddle. (Leave the front bolt in place, to preserve the correct saddle angle.)

Slide the lower tube of the post up over the stanchion to expose the cartridge and the actuator lock bolts. Remove the lock bolts with a 2mm Allen key, then slide the actuator and foam washer off the cartridge push rod. Remove the cartridge from the lower tube and clean all parts.

Working on the stanchion, remove the two split bushings and three guide pins, followed by the mid cap. Check for wear, and clean carefully with isopropyl alcohol and rags. If the parts are still in good condition, you can reuse them. Otherwise, replace them, using a OneUp dropper service kit.

Slide the lower tube back onto the stanchion, lining up the ONE logo with the two guide pins. Thread the mid cap onto the lower tube, tightening by hand or with a strap wrench. Replace the cartridge in the stanchion and fit the rubber O-ring over the valve, followed by the cartridge lockring.

Under the saddle clamp is an air valve (for returnspeed adjustment). To access the post internals, remove the dust cap and use pliers to unscrew the silver lockring from the valve (note its orientation), then flip the post and undo the green actuator on its base with a 14mm (V2.1)/17mm (V2.0) wrench.

Flip the post and remove the rubber O-ring from the air valve’s base. Then use a large strap wrench to undo (anticlockwise) the mid cap assembly, where the stanchion exits the lower tube. This can be tight. Remove the lower tube and clean inside with isopropyl alcohol and a lint-free cloth.

Start rebuilding the dropper, by greasing inside the mid cap and pushing it back onto the stanchion. Be careful not to scratch the stanchion with the hard plastic dust seal of the mid cap. Grease the split bushings and pins, and place them back on the stanchion; the grease will help hold them in place.

Insert the push rod into the base of the cartridge, and replace the foam washer and actuator. Fit the two guide bolts and tighten with a 2mm Allen key. Screw the actuator into the base of the lower tube (take care not to cross-thread). Trigger the actuator and set the pressure to 250-300 psi.