Oil leaking from a rear shock

There is oil on the body of a rear shock, round the seal where the rod enters, or oily dirt on the spring. The damper inside is losing its oil, so it will soon stop controlling the spring and the rear will bounce. Most commuter shocks are sealed units that cannot be refilled or resealed at home; a leaking shock is replaced.

Is it safe to ride?

Ride with care if the leak is small and the rear does not bounce. If oil is reaching the rear tyre or brake, do not ride: clean it off and fix the leak first.

Quick checks first

• Wipe the shock clean and ride a short distance. Is it wet again?
• Is the oil really from the shock, or from the chain, engine or fork above?
• Bounce test: does the rear bounce more than once?
• Is the shock rod rusty or pitted?

Diagnose it step by step

1After wiping clean and riding, is the shock body wet again at the rod seal?

• Yes: go to step 2.
• No: the oil came from somewhere else. Chain lube flung onto the shock is common: see Chain is dry, rusty or has stiff links. Engine oil: Oil leaking under the bike.

2Does the rear bounce more than once in the bounce test?

• Yes: the damper has lost oil. Replace the shock (both, on twin shocks). See Check the rear shock absorbers.
• No: go to step 3.

3Is the shock rod rusty, pitted or bent?

• Yes: the seal will keep leaking. Replace the shock.
• No: go to step 4.

4Is the shock a sealed unit (no refill or rebuild parts sold)?

• Yes: replace it. Do not try to open a gas-charged shock: it is under pressure.
• No (rebuildable shock with parts available): a suspension workshop can reseal it.

5After replacing, are both shocks on the same preload step?

• Set them with Adjust rear spring preload.

Buying replacement shocks: match the eye-to-eye length, top and bottom mount type, and the bike model. Replace twin shocks as a pair so both sides behave the same.

Causes, most likely first