Super73 S2: front fork leaks oil, won't hold air or keeps bottoming out

Your Super73 S2's front fork has oil on the stanchions, goes soft after you pump it up, or bottoms out over ordinary bumps. Super73's support article on the S2 fork lists exactly these three symptoms: oil leaking from the fork, the fork not holding air pressure, and frequent bottoming out (Super73 S2 fork article). Short answer: the left leg holds the air and the right leg holds the damping oil. Failed air seals on the left let air out, and failed seals in the right leg's damping reservoir let oil out. Before blaming seals, set the pressure correctly with a shock pump.

Most likely cause

Super73 names two seal failures (Super73 S2 fork article):

• Worn or failed air seals in the left stanchion. The fork can't hold pressure, so it sinks and bottoms out.
• Failed seals in the rebound fluid reservoir in the right stanchion, which lets oil leak out.

Other causes to rule out

• Pressure that was never set for your weight. The S2 handbook gives a suggested starting pressure chart by rider weight, with limits of 70 PSI minimum and 150 PSI maximum (S2 handbook).
• A tire pump instead of a shock pump. Super73 says a tire pump can let out too much air when you disconnect and struggles to reach fork pressures (Super73 S2 fork article).
• Lockout set high. With lockout turned up, little or no compression is a setting, not a fault (same article).
• Rebound and lockout not set for your weight (same article).

How to confirm

1. Find the air valve on the top of the left stanchion and remove the cap (S2 handbook).
2. Use a shock pump and set the starting pressure for your weight from the chart in your handbook (S2 handbook). Refit the cap.
3. Set the lockout (top knob, right stanchion) and rebound (bottom knob, right stanchion) as the handbook describes for your weight (Super73 S2 fork article).
4. Check sag. The handbook suggests about 20mm, measured at the bumper on the lower right stanchion (S2 handbook).
5. Leave the bike overnight and check pressure again with the shock pump. A fork that has lost pressure points to the left air seals.
6. Wipe the stanchions clean, ride a short loop, and look for fresh oil. Take a photo or short video of any leak for Super73 (Super73 S2 fork article).

Fix options

Set pressure, sag, lockout and rebound (easy)

Free with a shock pump. Fixes bottoming out when the cause is setup rather than seals. The handbook also suggests checking suspension monthly and greasing and tightening hardware about every six months, depending on use (S2 handbook).

Replace the fork (moderate, through Super73)

If seals have failed, Super73 says the fork needs a full replacement and its support team helps you order one (Super73 S2 fork article). Super73 doesn't list a seal kit in that article. Open a ticket with your photos or video. Fitting a fork means removing the front wheel, brake and handlebar stem, then setting headset preload, so a shop is the safer choice if you haven't done it before. Super73's support hub links its replacement parts store and service centers (Super73 support).

Parts

• Suspension fork (Super73 S2 replacement)

Videos

When to get a pro

Get the fork swapped by a shop or a Super73 service center if you aren't confident setting headset preload and brake alignment. Stop riding if the fork clunks, knocks or feels loose in the frame. See Super73 troubleshooting and when to call a pro.

Sources

• Super73 S2 fork article, support.super73.com
• S2 handbook, cdn.shopify.com
• Super73 support, super73.com
• How To Replace Your Front Fork for Super73 S1/S2/SG, youtube.com

Stuck after these checks? Find a shop near you.