Basic suspension fork service

Preparation and cleanup

Performing a lower leg service on a suspension fork keeps the seals sliding smoothly and protects the expensive stanchions from wear. Unlike a complex rear shock overhaul, this is a routine job that can be completed on a clean workbench. You should clear away any nearby projects, whether you are in the middle of a shifter cable replacement or just finished installing a rear rack on a city bike. Clean the entire fork thoroughly before you begin to keep grit from entering the internal chambers.

Position the bicycle securely. If you do not have a work stand, you can carefully clamp the seatpost or work with the fork removed entirely. Place a drain pan directly beneath the fork lowers to catch the old bath oil. Grab your tools, including a plastic mallet, some isopropyl alcohol, a set of hex wrenches, and your new dust wipers. Keep a roll of shop towels close at hand, as things will inevitably get oily during the removal process.

Removing the lower legs

Unthread the rebound adjuster knob from the bottom of the right fork leg and set it aside safely. Use a hex wrench to loosen the foot bolts on both sides by about three full turns, but do not remove them completely yet. Tap the bolt heads gently with your plastic mallet to dislodge the internal press-fit shafts from the lower casting. You will feel a distinct release as the shafts break free… this is the moment the old oil begins to seep out.

Remove the foot bolts completely and pull the lower legs straight down off the upper stanchions. Let the remaining bath oil drain into your pan. While the parts drain, take a moment to inspect your other gear nearby; a bike with flat pedals is excellent for testing suspension feel in the driveway, while your race rig might need a tubeless tire setup check before the next trail ride. Set the lowers aside on a clean rag.

Replacing seals and reassembly

Pry the old dust seals out using a wrench or a specialized seal puller, taking care not to scratch the metal seat. Clean the inside of the lowers with isopropyl alcohol and a lint-free cloth. Soak your new foam rings in fresh suspension oil, press them into place, and then press the new dust wipers in using a proper seal driver tool. “A crooked seal will leak immediately,” so take your time to push them in perfectly flush.

Slide the lowers back onto the stanchions just past the first seal barrier, but do not push them all the way up. Invert the fork slightly and inject the manufacturer-recommended amount of bath oil — usually between 5 and 15 milliliters — into the bottom of each leg port using a clean syringe. Slide the lowers the rest of the way on, reinstall the foot bolts to their proper tightness, and pop the rebound knob back on.