The Fox 38 Rhythm suspension fork is engineered for aggressive trail and enduro riding, offering strength, stiffness, and dependable damping performance. Designed to handle rough descents and high-impact terrain, this fork integrates technologies from Fox’s high-end lines while keeping accessibility in mind. This guide delivers a thorough overview of how to install, adjust, maintain, and optimize the Fox 38 Rhythm fork to enhance comfort and control.
Tools Required:
- Torque wrench [paid link] with appropriate bits (4mm, 5mm, 6mm)
- Crown race setter and star nut setter
- Suspension pump
- Allen wrenches [paid link]
- Caliper or rotor truing tool (for brake setup)
- Clean rag and suspension-specific grease
- Suspension oil and seal kit (for service)
- Isopropyl alcohol
Installation of the Fox 38 Rhythm
Correct installation is the foundation of performance and safety. Begin by preparing the steerer tube and crown race.
Steerer Preparation and Mounting:
Cut the steerer tube to the correct length for your frame and headset stack. Ensure a clean, square cut. Install the crown race with a race setter, and fit the star nut using a star nut setter to ensure proper alignment.
Mounting the Fork:
Insert the fork into the head tube, slide on headset components, and tighten the top cap and stem bolts to the manufacturer’s torque specs. Ensure there is no play in the headset and that steering is smooth.
Brake and Rotor Setup:
Mount the front caliper using the correct adapter for your rotor size. Align it carefully to prevent rotor rub. Torque bolts to specification, and check lever feel.
Adjusting the Suspension for Comfort and Control
The 38 Rhythm uses the GRIP damper and an air spring, offering extensive tunability with minimal complexity. To maximize comfort, dial in sag, rebound, and compression based on rider weight and trail preference.
Setting Sag
With riding gear on, place the bike against a wall and gently sit in riding position. Bounce slightly to overcome stiction and allow the fork to settle. Measure the exposed stanchion and calculate sag. For trail use, 15–20% sag is typical (around 25–35mm on a 180mm fork). Add or release air using a suspension pump to achieve target sag.
Rebound Damping
Turn the red rebound dial clockwise for slower rebound, counterclockwise for faster return. Adjust until the fork returns quickly but without “bucking” the front end. For comfort, aim for a controlled but not overly slow recovery.
Compression Damping
The GRIP damper includes an open-to-firm compression adjustment dial. For comfort and traction, leave the setting closer to open. Increase firmness only if pedal bob is noticeable or terrain is extremely smooth.
Maintenance and Service Intervals
Proper maintenance preserves performance and fork longevity. Fox recommends periodic service based on ride hours and conditions.
Routine Cleaning
After each ride, wipe stanchions with a clean rag. Avoid pressure washing directly at seals to prevent contamination. Check for oil seepage and dirt accumulation near the wipers.
Lower Leg Service
Every 30–50 hours of riding, perform a lower leg service. This includes draining old oil, cleaning the internals, replacing foam rings, and replenishing with fresh bath oil. Use a seal kit and follow torque specs closely.
Full Damper and Air Spring Service
Around 100 hours or annually, complete a full service including the air spring and damper. This involves more disassembly and requires suspension-specific tools and oil. Follow Fox’s service manual to maintain warranty compliance and performance standards.
Troubleshooting Common Set-Up Issues
Even with correct installation, issues may arise. Identifying and resolving them early can prevent ride interruptions.
Fork Feels Harsh or Non-Compliant:
Check air pressure and sag. Overinflation is common and leads to poor small bump sensitivity. Reduce pressure slightly and test again.
Fork Bottoms Out Too Easily:
Add air pressure or consider installing volume spacers to increase spring progression. These spacers can be added internally to change the air spring curve.
Excessive Rebound or Fork “Pogoing”:
Adjust rebound damping to a slower setting. If symptoms persist, inspect for air spring imbalance or internal damage.
Oil Leaks or Sticky Travel:
Indicates worn seals or contamination. Perform a lower leg service promptly. If issues remain, a full service may be necessary.
Customization and Optimization
The Fox 38 Rhythm offers several paths to tailor its feel and behavior to specific riding styles and terrains.
Volume Spacers
Adding volume spacers increases spring progression, preventing bottom-outs and enhancing mid-stroke support. Ideal for aggressive riders or those frequently hitting drops and jumps.
Aftermarket Upgrades
Although the Rhythm model doesn’t support the high-end GRIP2 damper, upgrading to higher-spec wiper seals or experimenting with different oil weights can improve small bump sensitivity and damping feel.
Adjusting Compression Curve
While limited to a single external compression dial, internal damper shims can be tuned by experienced technicians to alter the damping profile. This should only be done by professionals familiar with Fox damper architecture.
Compatibility with Drivetrain and Frame Standards
The 38 Rhythm uses a 15x110mm Boost axle, ensuring compatibility with modern Boost hub standards. It features a tapered steerer and supports rotor sizes from 180mm to 203mm without adapters.
Ensure your frame has adequate headtube length and internal routing capability, particularly if routing a front brake cable through a headset system.
Comparing the Fox 38 Rhythm to Similar Forks
While the 38 Rhythm targets affordability and performance, it differs from the 38 Performance and 38 Factory in a few key ways.
Weight and Construction:
The Rhythm uses a 6000-series aluminum chassis and lacks the Kashima coating seen on higher-end models. This results in slightly more friction but offers excellent durability.
Damper Differences:
The GRIP damper in the Rhythm is less adjustable than the GRIP2 in Performance Elite and Factory forks. However, for most trail riders, the GRIP damper provides reliable control and ease of use.
Price-to-Performance Ratio:
The Rhythm offers excellent performance per dollar, making it a solid choice for riders prioritizing value over elite-level adjustability.
Frequently Asked Questions
1. How much air pressure should I run in my Fox 38 Rhythm fork?
Refer to Fox’s air pressure chart based on rider weight. Typically, riders between 160–180 lbs use 85–95 psi for trail settings.
2. Can I upgrade the GRIP damper to a GRIP2 in the 38 Rhythm?
No, the Rhythm chassis is not compatible with the GRIP2 damper due to internal differences in the fork structure.
3. How often should I service the fork?
Perform lower leg service every 30–50 hours and a full service every 100 hours or annually, whichever comes first.
4. What travel options are available for the Fox 38 Rhythm?
It comes in travel options ranging from 160mm to 180mm, depending on your frame compatibility and riding style.
5. Why does my fork make a squelching noise when compressed?
This can result from trapped air or contaminated oil in the damper. A lower leg service typically resolves the issue.
6. Is the 38 Rhythm suitable for bike park use?
Yes, its robust chassis and damper make it capable of handling enduro and park-level abuse, though riders seeking advanced adjustability may consider upgrading to a Factory model.