The Fox 38 Rhythm is a purpose-built, performance-driven suspension fork, tailored for aggressive trail and enduro riding. Positioned below the Factory and Performance Elite series, the Rhythm variant offers excellent stiffness, ride control, and adjustability for riders seeking reliable suspension at a more accessible price point. This guide provides detailed steps for installation, adjustment, maintenance, troubleshooting, customization, and model comparison specific to the Fox 38 Rhythm.
Tools Required
- 5mm and 6mm Allen keys [paid link]
- Torque wrench [paid link]
- Suspension pump
- Digital caliper [paid link] or ruler (for sag measurement)
- Shock oil (if servicing)
- Clean rags and isopropyl alcohol
- Fox 20cc Float Fluid (for lower leg service)
- Suspension grease (compatible with Fox forks)
- 26mm socket or Fox-specific top cap tool
Installing the Fox 38 Rhythm Suspension Fork
Proper installation ensures long-term fork health and performance. Begin by confirming headtube and wheel compatibility. The Fox 38 Rhythm is built around a 1.5” tapered steerer and fits 29” wheels with a 44mm or 51mm offset.
Cut the steerer tube to length based on your frame and stem configuration, allowing at least 3mm above the stem for a top cap preload. Install the star nut or threaded insert, then press in the headset crown race using an appropriate tool.
Torque the headset components to the manufacturer’s specification. Insert the fork into the headtube and secure the stem and spacers. Tighten the stem bolts after preloading the headset bearing via the top cap. Mount the front wheel, ensuring axle and disc rotor alignment.
Adjusting the 38 Rhythm Fork for Optimal Performance
The 38 Rhythm uses the GRIP damper and EVOL air spring. While simpler than the GRIP2, the GRIP still offers a high level of control and user-friendly tuning. Focus on sag, air pressure, rebound, and compression settings.
Setting Sag and Air Pressure
Start by setting rider sag with all gear on. Fox recommends 15–20% sag. Use a ruler to measure the fork’s travel and calculate sag accordingly.
Inflate the air spring using a suspension pump. Fox provides an air pressure chart based on rider weight. After achieving the desired pressure, cycle the fork to equalize positive and negative chambers.
Tuning Rebound
The red knob at the bottom of the right leg controls rebound. Turning clockwise slows rebound; counterclockwise speeds it up. Start with the midpoint setting (around 8–10 clicks out from closed) and adjust based on trail feel. Too fast results in a pogo effect, while too slow makes the fork pack down on repeated hits.
Adjusting Compression
The blue dial atop the right leg adjusts low-speed compression. This controls how the fork resists slow compressions like braking, pedaling, and body movement. Start fully open and add clicks as needed to prevent excessive dive.
Routine Maintenance for Fox 38 Rhythm Forks
Regular maintenance extends the fork’s lifespan and ensures consistent performance. Lower leg service should be performed every 30–50 hours of riding.
Lower Leg Service
Remove the lower legs by unscrewing the bottom bolts and lightly tapping them to release. Clean the internals thoroughly. Replace foam rings, wiper seals if necessary, and apply suspension-specific grease.
Pour 20cc of Float Fluid into each leg before reinstalling. Tighten bolts to torque specs and cycle the fork to ensure smooth action.
Air Spring and Damper Service
At 125–200 hours, service the air spring and damper. This requires disassembly with specific tools and should be done by experienced users or a certified mechanic.
Troubleshooting Common Issues
If your fork feels harsh or inconsistent, check air pressure and sag first. Inadequate lubrication or dirty seals often cause stiction or loss of small-bump sensitivity. Perform a lower leg service and inspect bushings for wear.
Excessive dive can be mitigated with higher low-speed compression settings or increased air pressure. If rebound is too fast or slow despite adjustment, inspect the rebound circuit for debris or oil loss.
Unusual noises may signal a loose axle, worn bushings, or low oil volume. Check torque on all bolts and service intervals to correct.
Customizing the 38 Rhythm for Rider Preferences
While the Rhythm lacks the high-end tunability of GRIP2 forks, meaningful customization is still possible. Volume spacers can be added to adjust spring curve—more spacers result in a more progressive feel.
Fox provides tuning kits allowing one to modify the fork’s air volume. These are useful for riders who frequently bottom out or want a more supportive mid-stroke feel.
Aftermarket decals, axle upgrades, and bolt-on fender options are also available, letting riders personalize the look and function.
Compatibility with Other Drivetrain and Cockpit Components
The Fox 38 Rhythm integrates seamlessly with most modern mountain bike drivetrains and brake systems. It accepts 180mm to 203mm post-mount disc brakes and works with both Boost and non-Boost axle standards, depending on the specific model variant.
Ensure your wheel hub spacing matches the fork dropout width—typically 110mm Boost. Use a compatible rotor and caliper mount adapter for correct brake alignment.
For cockpit compatibility, the 1.5” tapered steerer fits standard stems and headsets for trail and enduro bikes. Remote lockout is not available on Rhythm forks, so manual dial access must be ensured in your cockpit setup.
Comparing the Fox 38 Rhythm to Similar Models
The 38 Rhythm shares its chassis with the higher-end 38 Factory but uses a simplified GRIP damper and lacks Kashima coating. While it’s heavier and less tunable than the Factory or Performance Elite versions, it delivers excellent performance for its price.
Compared to RockShox ZEB Select, the 38 Rhythm offers similar stiffness and ride support but features a slightly firmer mid-stroke feel and lower adjustability. Riders focused on aggressive riding without the need for precise tuning often prefer the Rhythm for its set-and-forget nature.
Frequently Asked Questions
1. Can I add volume spacers to the 38 Rhythm?
Yes. The fork is compatible with Fox air volume spacers. Adding spacers increases progression and reduces bottom-out.
2. How often should I service the 38 Rhythm?
Lower leg service is recommended every 30–50 hours. Full damper and air spring service should be done every 125–200 hours.
3. What’s the difference between GRIP and GRIP2 dampers?
The GRIP damper is simpler, with rebound and low-speed compression only. GRIP2 adds high-speed adjustments and is more tunable.
4. Is the 38 Rhythm suitable for downhill riding?
While it offers excellent stiffness, it’s best suited for enduro and aggressive trail riding. For dedicated downhill, a dual-crown fork is preferred.
5. Can I upgrade my GRIP damper to GRIP2?
Yes, but it requires damper replacement and tuning. It’s best done by a certified Fox service center.
6. What fork offset should I choose: 44mm or 51mm?
This depends on your bike’s geometry. A 44mm offset provides quicker handling, while 51mm offers more stability at speed.