AI 速览
- A 50-hour lower-leg oil swap is the single highest-ROI service on any air fork — under $20 of fluid protects a $300+ damper.
- Fox and RockShox use different bath oil viscosities — never substitute, the damper tune depends on the specific weight.
- Air can service on a rear shock takes 30 minutes and 5cc of Float Fluid; ignoring it dries out the dynamic seal.
- Full damper rebuilds at 100-200 hours need factory tools — most home mechanics should send the cartridge out.
/ 01
Why suspension service isn't optional
Mountain bike suspension is a hydraulic system running at 100+ PSI on films of oil thinner than 1mm. Every stroke shears the oil, every dusty ride grinds the wiper seal. Stiction climbs, mid-stroke support fades, and the damper goes from predictable to mysterious over a single season.
Service intervals aren't aspirational — they mark the point where bath oil has enough debris and lost enough viscosity to stop protecting the bushings. Skip them and the lower legs become a slow-abrasion lathe against the stanchion anodize.
/ 02
The service interval ladder
Service intervals — Fox 36 / RockShox Lyrik class forks
| Service | Interval | DIY? | Parts cost |
|---|---|---|---|
| Lower leg + air can | 50 hrs / 1 year | Yes | $18-25 |
| Air can only (rear shock) | 50 hrs | Yes | $15 |
| Full damper rebuild | 100 hrs Fox / 200 hrs RS | No* | $120-180 |
| Bushings + seals | 125-200 hrs | No | $80 + labor |
/ 03
Lower-leg service: the 50-hour DIY
Pull the lower bolts and drain the oil; what comes out tells you everything. Black and grey is normal bushing break-in. Silver and metallic means the stanchion anodize is wearing through. Milky means water got past the wiper.
Steps: remove wheel and brake caliper, loosen the foot nuts (8mm socket, but don't fully remove until the lowers are ready to drop), tap the lower leg down with a soft mallet to expose the air shaft. Wipe shafts, replace foam rings soaked in Fox 10wt gold bath oil, reassemble with the manual's volume — Fox 34: 10cc per side, Fox 36: 15cc per side, RockShox 32mm: 15cc of 0w-30 per side.
Torque sequence: thread the shaft bolt in finger-tight, then snug to 6.2 N·m on the Fox air-shaft side and 4.5 N·m on RockShox. The damper-side foot bolt uses the same spec. Over-torquing flexes the casting; under-torquing lets oil weep.
/ 04
Air can service
Rear shocks are simpler. Let the air out slowly with the pump attached, thread off the air can by hand or with a strap wrench, wipe the dynamic seal, and reapply a thin film of 0w-30 (RockShox) or Float Fluid (Fox). Reassemble and recharge to rider weight plus 5-10 PSI for sag.
Skip this and the seal runs dry — a sticky shock with a clunk on rebound is the result. The can threads are 1.5mm pitch; cross-thread them and you'll chase the thread for an hour.
/ 05
When to send out the damper
The damper is a pressurized IFP cartridge on Fox and a bladder design on RockShox. Both need a nitrogen charge or vacuum bleed that isn't realistic at home without the proper fixture. When the fork sucks down on fast hits or the lockout pulses, send it out — past the service interval, a $150 rebuild becomes a $400 replacement.
/ 06
Tools and supplies
Suspension service kit for the home mechanic
| Tool | Why | Cost |
|---|---|---|
| 24mm socket (Fox) | Air shaft top cap | $8 |
| Strap wrench | Air can removal | $15 |
| Fox 10wt gold bath oil | Lower leg lube (Fox) | $15 / 0.5L |
| RockShox 0w-30 bath oil | Lower leg lube (RS) | $15 / 0.5L |
| SRP butter or Slickoleum | Wiper seal grease | $12 |
| Torque wrench (2-20 N·m) | Foot bolts and shaft bolts | $40 |
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