The Fox 40 Factory suspension fork is a premier offering designed specifically for downhill racing and aggressive enduro riding. It stands as a benchmark for performance, combining cutting-edge damping technologies, superior chassis stiffness, and extensive tuning capabilities. This guide covers every aspect of the 40 Factory fork, from installation to optimization, ensuring riders can extract the highest performance possible from their equipment.

Tools Required

• Torque wrench [paid link]
• Crown race setter
• Allen key set (2mm to 8mm)
• Suspension pump
• Cassette lockring tool [paid link] (for rotor installation)
• Shock oil and seals (for maintenance)
• Suspension grease
• Caliper alignment tool

Installation Guidelines

Installing the Fox 40 Factory requires careful attention to compatibility and proper torque values. Begin by confirming the steerer tube length suits your frame’s head tube, and cut it precisely if necessary. Install the crown race on the steerer using the correct tool, followed by the lower crown and stem assembly. Tighten the crown bolts to manufacturer-specified torque values, typically around 5 Nm.

With the fork securely mounted, attach the front wheel and brake caliper. Fox 40 Factory models use a 20mm thru-axle and are optimized for 203mm or larger rotors. Use a caliper alignment tool to ensure the brake system is centered, reducing pad drag and enhancing modulation.

Adjustment Procedures

One of the standout features of the 40 Factory fork is its broad range of damping and spring adjustments. It comes equipped with Fox’s GRIP2 damper, offering high- and low-speed compression and rebound adjustments.

To set up the fork:

• Begin with sag adjustment using the air spring. Use a suspension pump to inflate the fork to the recommended pressure based on rider weight.
• Set rebound by turning the red knob on the bottom of the right fork leg. Adjust low-speed rebound first, then high-speed rebound to match terrain needs.
• Use the blue and black dials on the top right leg to adjust low- and high-speed compression, respectively. Start with base settings and fine-tune on the trail for improved control.

The EVOL air spring in the left leg enhances small bump sensitivity and mid-stroke support. For advanced tuning, tokens can be added or removed to alter air spring progression.

Maintenance Overview

Regular maintenance ensures long-term performance. Fox recommends a 30-hour service interval for dust wiper cleaning and oil top-offs, with a full damper and air spring overhaul at 100 hours.

Maintenance steps include:

• Removing lowers to clean and inspect dust wipers.
• Replacing oil with the correct volume and viscosity, usually 20wt Gold for lowers and 5wt Teflon-infused oil for the damper.
• Re-lubricating seals and stanchions to reduce friction and improve small bump compliance.

Routine air spring inspection includes checking for debris or oil contamination, which can affect performance and longevity.

Troubleshooting Common Issues

Several setup challenges can arise, especially when tuning for aggressive riding conditions. Excessive harshness over small bumps usually indicates too much compression damping or insufficient sag. In this case, reduce low-speed compression or decrease air pressure slightly.

If the fork rides too deep in its travel, either increase air pressure or install additional volume spacers to make the spring curve more progressive. For poor rebound recovery, especially after repeated hits, increase high-speed rebound damping.

Persistent oil leaks near the seals are typically due to worn or improperly lubricated dust wipers. Replace the seals and ensure proper lubrication during reassembly.

Customization and Performance Optimization

The 40 Factory fork provides extensive opportunities for customization. Riders can tune the GRIP2 damper to suit their terrain preferences, adjusting for flowy bike park trails or steep, technical descents. Volume spacers allow for tailoring the fork’s mid-stroke support and bottom-out resistance.

To enhance steering precision, consider pairing the fork with a direct-mount stem. This reduces flex and allows for more immediate handling feedback. Brake upgrades, such as 220mm rotors or higher-end calipers, further complement the fork’s capabilities by increasing stopping power under high-speed descents.

Model Comparison: Fox 40 Factory vs. Fox 40 Performance Elite

While both forks share the same chassis and air spring architecture, the Factory version is distinguished by the inclusion of the GRIP2 damper and Kashima-coated stanchions. The Performance Elite uses a black anodized finish and may include a simpler GRIP damper.

Kashima coating offers reduced friction and improved durability, particularly beneficial for riders who frequently encounter wet and muddy conditions. The GRIP2 damper, with independent high- and low-speed adjusters, delivers superior fine-tuning potential compared to the single-dial GRIP system.

Compatibility with Drivetrain and Chassis Components

The 40 Factory fork is designed for downhill frames with 1.5″ head tubes or tapered configurations. It requires a compatible 20mm axle hub and is best suited for 27.5″ or 29″ wheels, depending on the model variant. Ensure your frame accommodates the axle-to-crown height and offset to maintain proper geometry and handling characteristics.

It also integrates well with full Shimano or SRAM DH drivetrains. The fork’s structural rigidity supports high braking forces, making it ideal for use with powerful four-piston hydraulic brakes.

Conclusion

The Fox 40 Factory suspension fork stands out as one of the most advanced and customizable forks in downhill cycling. Its precision-engineered damping, robust air spring, and structural stiffness make it an ideal choice for elite racers and aggressive trail riders alike. With regular maintenance and thoughtful tuning, the 40 Factory delivers unmatched control, comfort, and confidence on the most demanding terrain.