Oil Lock Case / Bottoming Cone

Older bikes used chrome steel inner tubes clamped in the triple trees, sliding inside aluminium outer cases with cast axle clamps — the "Conventional" front fork. Most modern road and offroad sport bikes use Up-Side Down (USD) forks with alloy upper tubes and separate axle lug feet. Between an axle holder foot and an inner tube an oil lock case or bottoming cone keeps the assembly liquid tight and can locate the fork's compression bump rubber.

Function and service role of oil lock cases and bottoming cones

Prevent oil leaks between inner tube and axle lug while retaining damping oil
Provide a seating for compression bump rubbers and limit travel to avoid harsh bottoming
Available as complete inner tube assemblies or as separate oil lock cases, seals and spacers for service
Used with axle lugs, retaining clips, set screws and rebound adjusters in fork rebuilds

We sell axle internals and rebuild parts including Axle Lug Internals and offer guidance in our clicker setup guide. For tube options and coatings see our bigger suspension budget article, and maintenance tips at bike maintenance & repair. Protectors and covers are in outer tube protectors & covers, and we supply factory racing kit axle lugs plus universal holeshot clamps.