The Fox Float 40 Factory eMTB suspension fork is a high-performance downhill and enduro fork specifically engineered for electric mountain bikes. With its GRIP2 damper, Kashima-coated stanchions, and advanced air spring tuning capabilities, it offers precision performance under demanding riding conditions. This guide is designed to help eMTB riders properly install, tune, and maintain the Float 40 Factory fork for optimal ride quality and durability.
Tools Required
- 6 mm and 4 mm Allen wrenches [paid link]
- Torque wrench [paid link] with Nm scale
- Suspension pump with pressure gauge
- Shock oil (Fox 20wt Gold or specified)
- Clean rags and isopropyl alcohol
- Torque bit set (for crown bolts if applicable)
- Digital caliper [paid link] or ruler
- Suspension setup chart (provided by Fox)
Installing the Float 40 Factory eMTB Fork
Correct installation is essential for performance and rider safety. Before proceeding, inspect the steerer tube, axle interfaces, and brake mounts.
Fork Steerer Tube Preparation:
Ensure the steerer tube is cut to the appropriate length for your frame. Use a cutting guide and deburr the edges. Install the star nut or compression plug based on your headset type.
Crown Race Installation:
Use a crown race setter to seat the race cleanly on the fork’s crown. This ensures smooth headset rotation.
Headset and Frame Assembly:
Insert the fork into the head tube and slide on headset spacers, the stem, and top cap. Use a torque wrench [paid link] to evenly tighten the stem bolts to manufacturer specs.
Front Brake Mounting:
Attach your disc caliper using the appropriate adapter for your rotor size. Align it for proper rotor clearance and avoid drag.
Thru-Axle Wheel Fitment:
Slide the axle through the dropout and hub, tightening to the specified torque value. Make sure the wheel is centered.
Adjusting Air Spring Pressure and Sag
Proper air pressure tuning is foundational for the Float 40’s performance. Fox recommends setting sag to 15–20% of fork travel.
Calculating Sag:
Use the o-ring method. Slide the o-ring down to the fork seal, have the rider sit on the bike in full gear, then measure the compression.
Setting Air Pressure:
Attach a suspension pump to the air valve. Inflate the fork based on rider weight. For example, a 180 lb rider may need around 90 psi. Consult the Fox tuning chart for specifics.
Volume Spacer Tuning:
The Float 40 allows for internal air volume tuning using volume spacers. More spacers provide a firmer, progressive feel ideal for aggressive descents. Fewer spacers result in a linear feel suitable for mixed terrain.
GRIP2 Damper: Compression and Rebound Tuning
The Float 40 Factory is equipped with the GRIP2 damper, offering external adjustment for high-speed and low-speed compression and rebound.
Low-Speed Compression (LSC):
Controls fork movement during gradual terrain changes. Begin with the middle setting and adjust based on pedal bob and comfort.
High-Speed Compression (HSC):
Manages big hits and fast impacts. Increase HSC if bottoming out occurs. Decrease for more sensitivity on fast trails.
Low-Speed Rebound (LSR):
Affects how fast the fork extends after slow compression. Too fast results in bounce; too slow leads to packing up.
High-Speed Rebound (HSR):
Tailors fork return after big impacts. Start with Fox’s factory baseline and fine-tune according to riding style and terrain.
Troubleshooting Common Setup Issues
Even with careful tuning, issues can arise. Recognizing these problems early prevents long-term damage.
Fork Feels Too Harsh:
Check if air pressure is too high or if too many volume spacers are installed. Reduce LSC or HSC slightly to soften the feel.
Bottoming Out Frequently:
Add air pressure or install an additional volume spacer. Increase HSC damping incrementally.
Inconsistent Rebound:
This may be due to oil contamination or air in the damper circuit. Service the damper if rebound behavior feels erratic.
Noise During Compression:
A common culprit is dry seals. Apply suspension-specific lubrication to fork stanchions or check for bushing wear.
Routine Maintenance Schedule
Keeping the Float 40 Factory fork in top condition requires periodic servicing.
After Every Ride:
Wipe down stanchions and inspect seals for dirt or damage. Compress the fork a few times to spread oil.
Every 30 Hours:
Clean and relube dust wipers. Check for proper air pressure and adjust as needed. Inspect all bolts for torque.
Every 100 Hours or Annually:
Perform a full lower leg service. Replace foam rings, inspect bushings, and refresh the damper and air spring oil.
Customizing Performance for Different Terrain
The Float 40 Factory’s adjustability makes it suitable for various trail types and rider preferences.
Bike Park Riding:
Increase HSC and reduce LSR slightly for controlled landings. Add one volume spacer for better ramp-up.
Enduro Trails:
Use a balanced LSC and HSC setting for mixed-speed terrain. Moderate sag (18%) helps preserve travel for descents.
Technical Descents:
Increase sag slightly for more traction. Dial in slower rebound to maintain front wheel contact.
Compatibility with eMTB Drivetrains and Frames
The Float 40 Factory is built for eMTB-specific geometries and weights.
Frame Compatibility:
Supports modern head tube standards including tapered 1.5″ and 1 1/8″ steerer designs. Confirm crown-to-axle length matches your bike’s intended geometry.
Brake Mounting:
Uses 203mm post mount. Compatible with larger rotors using the appropriate adapters.
Wheel and Axle Fitment:
Designed for 29” wheels with 110mm Boost spacing and 20mm thru-axles. Ensure hub spacing and axle diameter match your fork configuration.
Comparing Float 40 Factory to Similar Models
When evaluating alternatives, it’s important to weigh features and tuning capacity.
Fox 38 Factory:
Slightly lighter and better suited for trail and aggressive all-mountain riding. However, it lacks the dual crown stiffness of the Float 40.
RockShox Boxxer Ultimate:
Offers a comparable dual crown chassis with similar travel, but uses the Charger 3 damper. Fox’s GRIP2 provides more fine-tuning for rebound and compression.
Öhlins DH38 M.1:
High-end competition fork with coil and air options. Fox Float 40 remains the preferred choice for riders favoring air spring adjustability.
FAQs
How do I know if my fork needs a full service?
If you notice oil leaks, spongy travel, or inconsistent damping, it’s time for a 100-hour service.
Can I convert my Float 40 for different travel?
Yes, but it requires a different air shaft assembly. Fox provides tuning kits for travel conversion within the fork’s supported range.
Is the Float 40 Factory eMTB-specific or can I use it on a regular downhill bike?
Though optimized for eMTBs, it can be used on standard downhill bikes as long as frame geometry and axle spacing match.
What’s the ideal rebound setting?
There’s no universal setting. Start from Fox’s base tune and adjust according to your weight, terrain, and speed preference.
Why is my fork making a top-out clunk?
This could indicate insufficient rebound damping or a worn rebound circuit. Inspect the damper and consider a rebuild if persistent.
Can I install a coil spring in the Float 40 Factory?
No, this model is air spring only. Riders seeking coil feel may want to explore other models in Fox’s or competitor lines.