The Fox 38 Rhythm is a performance-level enduro and all-mountain suspension fork, known for its robustness, high stiffness-to-weight ratio, and adjustability. This fork is built for aggressive trail riders who demand precision, control, and reliability on technical descents. In this review, we will explore the installation process, fine-tuning adjustments, ongoing maintenance, and performance optimization of the Fox 38 Rhythm, along with common setup issues and compatibility insights.

Tools Required

• 6mm and 5mm Allen wrenches [paid link]
• Torque wrench [paid link] with Nm settings
• Star nut setter (if installing a new steerer tube)
• Crown race setting tool
• Suspension-specific grease
• Shock pump (up to 300 psi)
• Isopropyl alcohol and clean cloth
• Fox volume spacer kit (optional)

Installation Procedure

The Fox 38 Rhythm uses a straight 1.5″ to 1 1/8″ tapered steerer tube and is compatible with modern tapered headsets. It is available in Boost spacing (110mm) and fits 29″ wheels.

Begin by inserting the steerer tube through the headset. Trim to length if needed and install the star nut or insert if using a threaded compression plug for carbon steerer compatibility. Tighten the headset cap and stem bolts to manufacturer torque specifications.

Ensure the thru-axle system is correctly torqued and aligned. The Fox 38 Rhythm utilizes a 15mm x 110mm Boost QR system with a pinch bolt on the lowers to maintain fork leg alignment. Before torquing, compress the fork once to let the dropouts settle evenly.

Adjustment and Fine-Tuning

The 38 Rhythm features a GRIP damper and a self-equalizing EVOL air spring. Unlike the FIT GRIP2 found in higher-end models, GRIP is a closed cartridge system with a simpler layout—ideal for riders seeking fewer maintenance demands without sacrificing trail performance.

Air Spring Setup:
Start by setting the rider’s weight and sag. The Fox 38 Rhythm is designed around 15-20% sag. Use a shock pump to inflate the air spring via the Schrader valve on the left stanchion. Check sag with the rider in full gear, seated on the bike in a neutral position. Use the O-ring indicator on the stanchion for sag measurement.

Rebound Adjustment:
Located at the bottom of the right leg, the rebound dial adjusts how quickly the fork returns to its full extension. Start with the factory-recommended setting and fine-tune based on terrain and rider feel.

Compression Adjustment:
The top right crown hosts the compression dial. This adjusts the damping under compression, helping riders dial in support for climbing and descending. For general trail use, mid-setting provides balanced responsiveness. For aggressive descents, increase low-speed compression to resist brake dive and harsh impacts.

Maintenance and Service Intervals

Regular maintenance ensures consistent performance and longevity.

• Every 30 hours: Clean stanchions, inspect for wear, and replace wiper seals if contaminated.
• Every 50 hours: Replace lower leg oil, clean internals, inspect bushings.
• Every 100+ hours: Complete damper service including air spring inspection, damper bleed, and replacement of wear items.

Use only Fox-approved suspension fluid and grease. Avoid over-lubrication, as excess oil can attract dirt, increasing friction and wear.

Troubleshooting Common Setup Issues

Stiction or Harsh Initial Stroke:
Often caused by dry or dirty seals. Clean stanchions and add a small amount of suspension-specific lubricant. If the problem persists, consider a lower leg service.

Inconsistent Rebound:
Check for proper air pressure and inspect for trapped air in the negative spring chamber. A full air spring service may be necessary.

Leaking Oil at Dust Wipers:
Indicates worn seals or overfilled lower legs. Perform a seal and oil service promptly to prevent bushing damage.

Customization and Performance Optimization

To further tailor the ride:

Volume Spacers:
The 38 Rhythm allows for the installation of air volume spacers. Adding spacers increases progression, preventing bottom-out on big hits. Removing them softens the end stroke, ideal for smoother trails or lighter riders.

Aftermarket Damper Upgrade:
While the GRIP damper performs admirably, riders seeking more tuning range can retrofit a GRIP2 cartridge for enhanced adjustability—ideal for racers and advanced riders.

Axle Stiffness Tuning:
The floating axle design ensures fork leg alignment and minimal binding. For riders sensitive to chassis stiffness, upgrading to the Kabolt-X axle can improve responsiveness and weight savings.

Compatibility With Other Drivetrain and Cockpit Components

The Fox 38 Rhythm is compatible with all major 1 1/8″ tapered headsets and most Boost-spaced front wheels. Its 180mm post-mount disc brake interface supports rotors up to 203mm with adapters.

It pairs well with:

• Wide-range 1x drivetrains, offering superior control on steep trails.
• Dropper posts, especially when routed through internally guided frames, due to extra front-end height.
• High-rise handlebars and short stems, complementing the fork’s tall axle-to-crown measurement and aiding in downhill body position.

Comparison With Similar Models

Compared to the Fox 38 Factory and Performance Elite:

• The Rhythm is slightly heavier due to its heavier stanchion coatings and steel upper assembly, but retains comparable chassis stiffness.
• The GRIP damper offers fewer adjustments than the GRIP2, yet it delivers strong small bump compliance and ease of use for general riders.
• The air spring and chassis are identical, meaning overall trail performance remains competitive.

Versus the RockShox ZEB Select:

• The 38 Rhythm offers slightly better small bump sensitivity and front-end stiffness.
• The ZEB may edge ahead in damper tuning flexibility with the Charger RC damper, but maintenance intervals and reliability favor Fox’s GRIP system.

Conclusion

The Fox 38 Rhythm is a purpose-built suspension fork that delivers outstanding performance for aggressive trail and enduro riders. With reliable damping, robust construction, and low-maintenance design, it is an ideal choice for riders who prioritize function over fine-tuning complexity. While it lacks some of the refinements of Fox’s top-tier offerings, its performance-to-price ratio makes it a standout option in the mid-tier suspension category.