Installing Your Fork  |  Before You Ride  |  Setting Sag |  Adjusting Rebound  |  Adjusting Bump Threshold  |  Changing Travel  |  Service Intervals  |  Important Safety Information


F100 weight
F80 weight

3.49 lbs./1.58 kg
3.43 lbs./1.56 kg

F100 travel The total amount the shock or fork compresses. On a shock it is measured using the eye-to-eye distance or shaft travel.
F80 travel

3.9 inches / 100 mm
3.1 inches / 80 mm


air spring pressure, rebound, bump threshold

spring/damper type

air/X damper

intended use

cross-country A style of bicycle riding that is defined by long rides, lightweight bicycles and stamina.


White Gold



Installing Your Fork

Be sure your fork is properly installed before proceeding. Clicking on the link above will take you to a new page.

Before You Ride

  1. Check that quick-release levers are properly adjusted and tightened.

  2. Clean the outside of your fork with soap and water and wipe dry with a soft dry rag. Do not spray water directly on the seal/upper tube junction. Do not use a high pressure washer on your fork.

  3. Inspect entire exterior of fork for damage. The fork should not be used if any of the exterior parts appear to be damaged. Please contact your local dealer or FOX Racing Shox for further inspection and repair.

  4. Check headset adjustment. If loose, adjust according to manufacturer’s recommendations.

  5. Check that brake cables or hoses are properly fastened.

  6. Check that the front and rear brakes operate properly on flat land.

Setting Sag

You can also view a Flash video on Setting Sag.

To get the best performance from your fork, it is necessary to set and adjust sag Amount a shock or fork compresses with the rider sitting on the bike in a normal riding position. Best measured with an assistant holding your bike up and with the rider in full riding gear. On a fork, it is helpful to place a ZIP tie around one of the upper tubes.. Generally, sag should be set to 15 – 25% of total fork travel.

  1. Unscrew the blue aircap (shown below) on top of the left fork leg to expose the Schrader valve.  

  1. Attach a FOX Racing Shox High Pressure Pump to the Schrader valve.

  2. Using the Air Spring Settings table below, pump your FLOAT Fox Load Optimum Air Technology. Delivers the performance of a coil spring with the adjustability and light weight of an air shock. fork to the appropriate setting using the FOX High Pressure Pump, then remove the pump.

  3. Install a zip tie with light friction on the upper tube and push it down until it contacts the fork seal.

  4. Carefully sit on the bike and assume a normal riding position. The fork should compress slightly.

  5. Being careful not to further compress the fork, dismount the bicycle. Measure the distance between the seal and the zip tie. This distance is sag.

  6. Compare your sag measurement to the Sag Setup table below.

    If your sag is lower than on the table
    , screw on the pump fitting, note the current air pressure setting and depress the black bleed-valve to reduce the gauge pressure by 5 psi. Measure sag again and repeat adjustment, if necessary.

    If your sag is higher than on the table
    , screw on the pump fitting, note the current air pressure setting and pump to increase the gauge pressure by 5 psi. Measure sag again and repeat adjustment if necessary.

  7. Screw the blue aircap back on, and go ride.



Rider Weight

Air Pressure

< 125 lbs.

45 psi

125 - 135 lbs.

50 psi

135 - 145 lbs.

55 psi

145 - 155 lbs.

65 psi

155 - 170 lbs.

75 psi

170 - 185 lbs.

85 psi

185 - 200 lbs.

95 psi

200 - 215 lbs.

105 psi

215 - 230 lbs

115 psi

230 - 250 lbs.

125 psi


sag setup




80 mm (3 1/8")

12mm (1/2")

20mm (3/4")

100 mm (4")

15mm (5/8")

25mm (1")


sag troubleshooting



Too much sag

(+) air pressure in 5psi increments

Too little sag

(-) air pressure in 5psi increments

Excessive bottoming

(+) air pressure in 5psi increments

Harsh ride; full travel not utilized

(-) air pressure in 5psi increments

Adjusting Rebound

The rebound knob (shown below) is located on the top of the right fork leg, and has 12 clicks of adjustment. Rebound controls the speed at which the fork extends after compressing. Turning the knob clockwise A motion that proceeds from the top to the right, then down and then to the left, and back to the top, like the clock's hands. slows down rebound; turning the knob counterclockwise The opposite direction of clockwise. speeds up rebound. As a starting point, turn the rebound adjuster knob all the way clockwise (full in) until it stops, then turn counterclockwise (out) 6 clicks.


Knob Setting
(clicks out from full in)

Setting Description

Tuning Tips

Setup Tips


Slow Rebound

Too slow and your fork will pack down and ride harsh.

If you increase your spring rate Force required to compress a spring one inch. or air pressure, you will need to slow down your rebound


(Factory setting)

Average Rebound



Fast Rebound

Too fast and you will experience poor traction and wheel hop.

If you decrease your spring rate or air pressure, you will need to speed up your rebound setting.

Adjusting Bump Threshold

Bump threshold is adjusted with the blue knob located on the bottom of the right fork leg. This gives the rider the ability to adjust the force required to cause the BrassMass valve to open, depending on the bump input from the trail. Turn the knob clockwise to make it harder for the BrassMass valve to open (higher bump threshold), counterclockwise to make it easier for the BrassMass valve to open (lower bump threshold).

There are 22 clicks of adjustment. The factory setting is full out (counterclockwise), then 6 clicks in (clockwise).

Knob Setting
(clicks out from full in)

Setting Description

Tuning Tips

Setup Tips



Provides firmest threshold.

Maximum pedaling efficiency with slight loss of slow-speed traction.


(Factory setting)





Provides low-speed compression damping to filter out rider-induced bob.

Good pedaling efficiency with increased slow-speed traction.

Changing Travel

Travel on your F100 fork can be lowered to 80mm by rearranging the internal travel spacers. After changing travel, check the fork for proper operation before riding. If there is noticeable play in the fork or if it makes strange noises, disassemble the fork and check for complete number and correct orientation of spacers.

An F100 can be lowered in travel to 80mm, but an F80 cannot be increased to 100mm.

Tools Required for Travel Change
Supplies Required for Travel Change
Learn how to use the FOX High Pressure Pump



Part Number

Part Name



1 qt. bottle of FOX Suspension Fluid (7 wt.)



5cc Pillow Pack of FOX FLOAT Fluid



Crush washer



32MM Cartridge Seal Kit (optional)

  1. Remove the blue air cap from the top of the left fork leg. Let the air out of the fork. Remove the left top cap with a 26mm socket 6-point socket wrench.

  2. Loosen the bottom nut 3-4 turns with a 10mm wrench. With a plastic mallet, gently tap the bottom of the shaft to disengage it from the lower leg. Allow oil to drain into a bucket. Remove the bottom nut and crush washer.

  3. Compress the fork as much as possible. The air piston will be visible about one inch below the top of the upper tube. Push the bottom of the air shaft upwards to push the air piston out of the top of the upper tube. Use a long, thin shaft screwdriver to push the bottom of the air shaft up through the hole in the bottom of the lower leg.

  4. Pull the air-shaft assembly from the fork. Refer to the drawings below and add or remove the appropriate spacer to achieve the desired travel.

Spacers snap onto the air shaft between the negative spring guide and topout plate, as shown in the travel spacer orientation drawing below.

  1. Lubricate the U-cup seal on the air piston with FOX FLOAT Fluid and re-install the air shaft assembly into the upper tube. Be sure to orient the U-cup seal as shown in the Seal Orientation drawing below.

  2. Push the shaft until it approaches the bottom hole of the fork. Do not push the shaft all the way through the bottom hole.

  3. Turn the fork upside down. Measure and pour 30cc of FOX Suspension Fluid through the bottom hole.

  4. Push the air shaft assembly up until the shaft comes through the bottom hole. Install the crush washer and bottom nut. Torque to 50 in-lbs.

  5. Turn the fork right side up. Pour 5cc of FOX FLOAT Fluid on top of the air piston.

  6. Lubricate the o-ring on the air topcap with FOX FLOAT Fluid.

  7. Re-install the topcap and torque to 165 in-lbs.

  8. Pump up the fork to the desired pressure and cycle it several times to check for proper operation.

  9. Re-install the blue air cap.

  10. You’re done. Go ride.

Travel Spacer Orientation

Seal Orientation