The Fox 38 Factory GRIP2 suspension fork is engineered for aggressive enduro and downhill riders who demand fine-tuned control over terrain. Its GRIP2 damper features high- and low-speed compression and rebound adjustability, allowing riders to optimize performance for varied conditions. This guide covers essential steps for installation, adjustment, maintenance, troubleshooting, and performance enhancement of the Fox 38 Factory GRIP2 fork.
Tools Required
- 5mm and 6mm Allen wrenches [paid link]
- Torque wrench [paid link]
- Suspension pump
- Shock oil and seal grease
- Clean rags and isopropyl alcohol
- Measuring calipers
- Digital level (for sag setting)
- Soft-jaw vise (for steerer installation)
Installation Procedure
Installing the Fox 38 Factory GRIP2 fork begins with correctly preparing the headset and steerer tube. Cut the steerer to the desired length, ensuring a clean and square finish. Use a star nut or compression plug compatible with carbon or alloy steerer tubes, depending on the headset type.
Insert the fork into the frame and align the headset bearings and spacers. Torque the stem bolts to manufacturer specifications (usually between 5–6 Nm). Ensure the front wheel is properly seated in the 15QR or Kabolt axle dropouts and that the axle is torqued to 19 Nm.
Check for headset play by applying the front brake and rocking the bike back and forth. If play exists, re-adjust headset preload and re-tighten the stem.
Setting Sag and Air Pressure
Correct sag is essential for suspension performance. Fox recommends a 15-20% sag setup for the 38 Factory fork. To determine sag:
- Wear full riding gear and mount the bike.
- Push down slightly to engage the suspension and then carefully return to a neutral position.
- Use the o-ring on the fork stanchion to measure the amount of travel used.
For a 170mm fork, a 20% sag equates to 34mm of travel. Adjust the air pressure via the Schrader valve on the top of the left leg using a suspension pump. Refer to Fox’s air pressure chart based on rider weight, fine-tuning if necessary for riding style.
Rebound and Compression Adjustment
The GRIP2 damper offers four key adjustments:
- High-Speed Compression (HSC): Located at the top of the right fork leg, adjust using a 6mm Allen. Turning clockwise increases compression damping for big hits and g-outs.
- Low-Speed Compression (LSC): Adjust with the outer dial surrounding the HSC adjuster. This affects brake dive and mid-stroke support.
- High-Speed Rebound (HSR): Found at the bottom of the right fork leg. More damping slows the fork return after large compressions.
- Low-Speed Rebound (LSR): The red knob at the bottom adjusts how quickly the fork rebounds from small bumps.
Begin with Fox’s recommended settings and adjust one click at a time. Use trail feedback to refine settings for comfort, traction, and control.
Routine Maintenance Schedule
Regular maintenance prolongs fork life and maintains optimal performance:
- Every 30 hours: Clean stanchions, inspect dust wipers, and apply suspension-specific oil or grease.
- Every 50 hours: Perform a lower leg service including oil replacement and seal inspection.
- Every 125 hours or annually: Complete damper service including air spring and damper rebuild using a full service kit.
Avoid using high-pressure water on seals or adjusting knobs. Store the bike vertically or inverted occasionally to lubricate foam rings and bushings.
Troubleshooting Common Issues
- Harsh Ride or Packing Down: Check for excessive HSC or low air pressure. Reduce HSC by 1–2 clicks and verify proper sag.
- Excessive Dive Under Braking: Increase LSC or add volume spacers to the air spring.
- Inconsistent Rebound: Air may be trapped in the damper. A damper bleed or rebuild is recommended.
- Fork Not Returning Fully: Inspect for negative air chamber issues or worn wiper seals causing stiction.
Systematically test one setting at a time to isolate performance concerns.
Customization and Volume Tuning
The air spring on the Fox 38 GRIP2 can be tuned using volume spacers to control the end-stroke ramp. More spacers result in a firmer end-stroke, ideal for aggressive riders or big drops. Fewer spacers provide a more linear feel for flow trails or lighter riders.
To install volume spacers:
- Release all air pressure.
- Unscrew the top cap using a cassette tool.
- Snap in the desired number of spacers (max allowed per travel spec).
- Reinstall cap and pressurize to desired PSI.
Always recheck sag after volume tuning as spring curves will change.
Compatibility With Other Drivetrain Components
The 38 Factory fork is compatible with a wide range of thru-axle 29″ wheels, Boost spacing (110mm), and tapered steerer tube frames. It works seamlessly with disc brakes using 180mm to 220mm rotors and post-mount calipers.
Ensure rotor size is supported and brake hose routing is clean. While the fork does not directly interact with drivetrain parts, check that front shifter and cable routing are clear of crown and stanchion contact.
Performance Comparison With Similar Models
Compared to the Fox 36 GRIP2, the 38 offers greater torsional stiffness and better support for enduro and downhill disciplines. It has a larger crown and stanchion profile and uses a floating axle system for improved alignment.
Against the RockShox ZEB Ultimate, the Fox 38 GRIP2 offers slightly more tuning granularity due to its four-way damper. However, the ZEB may feel more supple initially due to its Charger 3 damper architecture.
Riders preferring precision tuning and better chassis stiffness should lean toward the Fox 38 Factory GRIP2.
FAQs
1. What’s the ideal sag percentage for the Fox 38 GRIP2?
Fox recommends 15-20% sag, translating to around 25.5mm–34mm for a 170mm travel setup. Riders can fine-tune based on terrain and style.
2. How often should I service the Fox 38 Factory fork?
Minor servicing should occur every 30–50 hours. Full damper and air spring services are advised every 125 hours or annually.
3. Can I use the Fox 38 GRIP2 on a trail bike?
While technically possible, the fork’s weight and stiffness are designed for aggressive enduro or downhill use. It’s better suited for bikes with 160–180mm rear travel.
4. What are volume spacers and how do they affect performance?
Volume spacers modify the fork’s air spring curve, increasing progressiveness. More spacers prevent bottom-out but reduce small bump sensitivity.
5. Why does my fork feel sticky or slow to return?
This may indicate dry seals, inadequate lower leg lubrication, or damper issues. A service with fresh oil and inspection of internals is recommended.
6. Can I use the same settings on different trails?
Settings should be adjusted based on trail conditions. Steeper or rougher trails may require more HSC and rebound damping for control.