Home mechanic (basic tools) ยท Time: 15 to 30 min (editorial estimate) (estimate)
Many fork leaks start when a grain of sand or dried mud sticks under the lip of the oil seal and holds it open. Cleaning under the lip can stop the leak without taking the fork apart. It only works if the seal and the stanchion (the shiny inner tube) are not damaged. If the leak comes back quickly, the seals must be replaced.
Safety
- Support the bike securely.
- Fork oil on the brake disc or pads makes the brake slip. Cover the caliper with a rag, and clean the disc with brake cleaner afterwards. Oil-soaked pads must be replaced.
- Do not use a metal blade under the seal lip. It cuts the seal.
You need
- A thin, flexible plastic strip that will slide under the seal lip. Small purpose-made seal cleaning tools are sold; a strip cut from clean, stiff plastic film works too.
Steps
- Clean the stanchion and the top of the outer leg with a rag.
- Look at the stanchion where it slides through the seal. Rust pits, chips or scratches you can feel with a fingernail mean cleaning will not last. Go to Replace fork oil and seals.
- Gently lever the dust seal (the outer rubber cap) up and slide it up the tube. Do not scratch the tube.
- Wipe out the dirt you can now see on top of the oil seal.
- Wet the plastic strip with a drop of clean oil. Slide one edge under the oil seal lip, between the lip and the tube.
- Work the strip all the way round the tube, pulling up as you go to lift out grit. You may see dirty oil come out on the strip.
- Wipe the strip and repeat two or three times.
- Wipe the area clean, push the dust seal back down into place.
- Hold the front brake and pump the forks a few times. Wipe the tube again.
- Clean the brake disc with brake cleaner.
- Repeat on the other leg if it was leaking.
Check your work
- After pumping the forks 10 to 20 times and after a short ride, the tube is dry with no new oil ring.
- Check again after a week of riding.
If it did not fix the problem
- Leak comes back, or the tube is damaged: Replace fork oil and seals.
- Lost a lot of oil: the fork will feel soft and may bottom out. See Front forks bottom out.