The Fox 40 Factory fork remains one of the most revered components in the downhill mountain biking world. Designed for aggressive riding and precision control, the 40 Factory combines cutting-edge suspension technology with durable construction. With its purpose-built architecture, it excels in demanding trail conditions and downhill racing. This article explores the installation, adjustment, maintenance, and optimization of the Fox 40 Factory while also detailing compatibility and comparisons to similar forks.
Tools Required:
- 5mm and 6mm hex wrenches
- Torque wrench [paid link]
- Crown race setting tool
- Suspension pump
- Shock oil and service kit
- Caliper alignment tool
- Clean rags and isopropyl alcohol
Installation of the Fox 40 Factory
Proper installation ensures the fork performs as intended. The Fox 40 Factory is designed for tapered steerer tubes and 20mm thru-axle front hubs. Begin by verifying frame compatibility and fork length clearance.
The steer tube must be cut precisely to match the frame and stem height. Use a cutting guide to ensure a straight cut. Install the crown race and press it evenly to prevent binding during rotation. When installing the fork into the head tube, ensure the headset bearings are clean and properly greased.
Tighten the top cap and stem bolts using a torque wrench [paid link]. For dual-crown forks like the 40 Factory, equal torque on both upper and lower crowns is crucial to prevent stanchion misalignment.
Adjustment and Tuning Settings
The Fox 40 Factory offers a wide range of adjustability to fine-tune performance based on terrain and rider preference. Key tunable features include high-speed and low-speed compression, rebound damping, and air spring pressure.
Use the recommended air pressure chart provided by Fox as a starting point. Rebound should be adjusted based on rider weight and terrain type—faster rebound for smoother trails and slower for technical descents.
Compression tuning allows for control of fork movement under both pedaling and heavy impacts. Low-speed compression helps with support during cornering and braking, while high-speed compression deals with sudden hits like rock gardens.
Fine-tuning requires real-world testing. Record your baseline settings and adjust in small increments, noting the impact of each change. This ensures a consistent and controlled setup process.
Maintenance Guidelines
Routine maintenance is essential for long-term performance. Fox recommends lower leg service every 30 hours of ride time and a full damper and air spring service every 100 hours.
Begin by removing the front wheel and brake caliper. Drain old oil from the lower legs and inspect the seals and foam rings for wear. Clean all components with isopropyl alcohol and replace any worn parts.
Use only Fox-approved suspension oil to refill the lower legs. Grease the new dust wipers and carefully reinstall the lowers, ensuring proper engagement with the damper shafts. Torque all bolts to factory specifications.
For full damper service, specialized tools are required. If unfamiliar with the process, it’s advisable to consult a certified suspension technician.
Troubleshooting Common Issues
Several issues may arise during setup or use. If the fork feels harsh or unresponsive, check air pressure and rebound settings. A common mistake is running too little sag or too much compression damping.
If you notice oil leaks, inspect the dust seals and damper side for cracks or degradation. A noisy fork can indicate air in the damper or worn bushings. Inconsistent rebound speed often points to oil contamination or low oil levels.
Brake rubbing after fork installation is typically due to misaligned calipers or bent rotors. Re-align using a caliper tool and ensure the thru-axle is tightened to spec.
Customization and Performance Optimization
The Fox 40 Factory supports volume spacers, allowing riders to alter spring progression. Adding spacers increases bottom-out resistance, beneficial for aggressive riders or jump-heavy trails.
For those looking to minimize fork dive under braking, tuning the low-speed compression and adding a small volume spacer can help. Riders can also experiment with stanchion coatings and different crown heights to alter flex characteristics and front-end feel.
Fox offers factory tuning kits and custom damper tunes through their authorized service centers. This is ideal for competitive riders seeking tailored performance characteristics.
Compatibility with Drivetrain and Frame Components
The 40 Factory is compatible with boost-spacing hubs using adapters and requires a 20mm thru-axle. It works with both 27.5” and 29” wheel sizes, with different models specified for each.
Brake mount compatibility is post-mount only, with a minimum rotor size of 203mm. Ensure the frame supports dual-crown forks to avoid damage from crown interference with the downtube.
While drivetrain compatibility is not directly impacted by the fork, ensure cable routing accommodates the fork’s size and movement. Internal cable routing in frames may require special guides to avoid friction or wear.
Comparison with Similar Fork Models
Compared to the Fox 38, the 40 Factory is designed exclusively for downhill and freeride use. The 38 is more suitable for enduro due to its single crown and lighter weight.
Against the RockShox Boxxer Ultimate, the Fox 40 Factory offers a more refined damper system and stiffer chassis, providing improved control in high-speed descents. However, the Boxxer is lighter and slightly easier to service for the average mechanic.
In contrast with the Marzocchi Bomber 58, the Fox 40 Factory delivers better high-speed compression performance but at a premium price. The Bomber 58 is a more budget-conscious option with similar chassis stiffness but fewer tuning features.
Frequently Asked Questions
What is the recommended air pressure for the Fox 40 Factory?
Air pressure varies by rider weight and terrain. Fox provides a chart based on rider weight to help dial in the correct sag and pressure.
How often should I service my Fox 40 Factory fork?
Lower leg service is recommended every 30 hours of riding, with full service every 100 hours or annually, whichever comes first.
Can I use the Fox 40 Factory on an enduro bike?
While possible, the 40 Factory is intended for downhill bikes. It may interfere with frame geometry and is heavier than enduro-specific forks.
Does the Fox 40 Factory support volume spacers?
Yes, volume spacers can be added to the air spring to modify progression and bottom-out characteristics.
What tools do I need to service the Fox 40 Factory?
Basic tools include hex wrenches, a torque wrench, suspension pump, and oil. Full damper service requires Fox-specific tools.
Is the 40 Factory compatible with 29” wheels?
Yes, Fox offers 40 Factory variants for both 27.5” and 29” wheels. Ensure you purchase the correct model for your bike.
The Fox 40 Factory stands out as a premier choice for downhill riders seeking elite-level performance, robust construction, and superior tunability. Its rich feature set and proven race pedigree make it a reliable investment for serious mountain bikers.