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FOX D.O.S.S. Adjustable Seatpost

NOTE:  The FOX D.O.S.S. adjustable height seatpost is a three position, remotely activated and pneumatically controlled mechanical seatpost system. It is not a suspension seatpost product.

  • Diameter sizes: 30.9 or 31.6 mm
  • Seatpost drops: 4” (100 mm) or 5” (125 mm)
  • Remote lever activated
  • Pneumatic, adjustable speed return
  • Left or right side cable mounting
  • Two bolt, no slip saddle clamp design

Climb. Trail. Descend.

Climb. Trail. Descend. (CTD) is the integrated ride dynamics system from FOX that simplifies FOX product settings to coordinate and function more effectively, in any type of riding terrain.

Using the D.O.S.S. Adjustable Seatpost

Understand the following basics before using your FOX D.O.S.S. seatpost.

Installing the D.O.S.S. Adjustable Seatpost

CAUTION:  FOX products should be installed by a qualified bicycle service technician, in accordance with FOX installation specifications. If you have any doubts as to whether or not you can properly install the D.O.S.S. adjustable height seatpost on your bicycle, defer to a professionally trained bicycle service technician.

WARNING:  Improperly installed products can fail, causing the rider to lose control, potentially causing SERIOUS INJURY OR DEATH.

CAUTION:  Do not clamp your bike in a work stand by any portion of the upper seatpost or cable housing.

NOTE:  The anodized surface of the upper seatpost, like a rear shock body, serves to create an air seal. Always take every precaution to avoid causing abrasion damage to the anodized surface of the upper seatpost.

CAUTION:  Caution: After installation, be sure to test for all proper clearances.

Required Tools

CAUTION:  Be sure your seatpost is the correct outer diameter size to fit your bicycle seat tube inner diameter size. Using the incorrect size of the D.O.S.S. seatpost on your bicycle can lead to product damage, personal injury, or both.

  1. Remove the upper saddle clamp by loosening the saddle clamp bolts from the barrel nuts , keeping the spherical washers on the bolts in their original assembly orientation.
  2. After applying a light coating of grease to the lower seatpost, insert the seatpost assembly into the aluminum bicycle frame seat tube.

    NOTE:  Do not use grease with carbon fiber frames. Installing your seatpost with friction paste is an option for carbon fiber frames.

    WARNING:  Regardless of bicycle frame tube configuration, the best structural support is achieved when the D.O.S.S. seatpost is inserted at least to 1) the minimum insertion mark on the seatpost, AND 2) the minimum insertion point specified by the manufacturer of your bicycle frame. Neglecting these two items risks causing damage to the frame and seatpost, potentially causing SERIOUS INJURY OR DEATH.

    TIP: At this point, simply rotate the D.O.S.S. seatpost assembly in the seat tube to choose which side, right or left, to position the remote cable hanger .

    CAUTION:  Make sure the air chamber Schrader valve on the bottom of the seatpost assembly never touches any part of the frame, or the rear shock through the entire range of its travel.

    After adjusting for proper leg extension in Climb mode, tighten your seat collar binder bolt to the torque level specified in your bicycle owner’s manual.

    CAUTION:  Excessive seat tube collar binder bolt tightness can cause the upper seatpost to bind within the lower seatpost.

  1. Completely loosen the bar mount clamp bolt and open the bar mount clamp , to install the D.O.S.S. remote lever assembly on your handlebar.

    You do not need to remove the handlebar grip. The D.O.S.S. remote lever assembly can be installed on the right or left side of the handlebar, as well as underneath or on top, giving you a total of four setup possibilities from two configurations:

    • On the right side on top, or invert to install on the left side, underneath the handlebar
    • On the left side on top, or invert to install on the right side, underneath the handlebar

    WARNING:  Make sure that the D.O.S.S. remote lever does not interfere with normal brake and shift lever operation. Failure to do so can result in loss of control, potentially causing SERIOUS INJURY OR DEATH.

    NOTE:  To convert your D.O.S.S. remote lever assembly from a left top-mount lever assembly to a right or vice versa, see the “Converting the Remote Lever” section.

    Tighten the bar mount clamp bolt to 15 in-lb (1.7 N-m) torque for aluminum handlebars.

    CAUTION:  Always use less tightening torque for carbon fiber handlebars than you can do with aluminum. As a general rule, tighten the bar mount clamp on a carbon fiber handlebar only to the point of preventing remote lever assembly twist on the handlebar. Consult the bicycle or handlebar manufacturer’s documentation regarding the torque specification for your carbon fiber handlebar.

  1. Adjust the cable adjuster all the way in clockwise, then back out counter-clockwise a full turn, or four (4) clicks.
  2. With a large zip tie, install the cable housing guide on the lower seatpost.
  3. Make the cable housing as short as possible, allowing just enough slack to ensure smooth cable operation. Make sure to allow enough slack for full seatpost travel and steering clearance.

    TIP: Route your cable housing with the largest bend radius possible, to avoid sharp cable housing bends that add to cable and lever friction.

    NOTE:  The path for mounting the cable housing on your frame can vary, so carefully assess all your options before choosing.

    After matching up the cable housing with your chosen path on the bike frame, cut it to fit.

    CAUTION:  Be sure the cable housing does not interfere with the swingarm linkage, rear tire, clothing and riding gear, and steering clearance throughout the seatpost travel range. Never attach the cable housing to any part of your rear shock.

  4. Thread the cable through the remote lever assembly, exiting through the cable adjuster.

    NOTE:  The FOX D.O.S.S. adjustable height seatpost uses standard 1.1 or 1.2 mm shifter cable, 4 mm shifter cable housing, and 4 mm shifter cable housing ferrules.

  1. Lightly lubricate the cable, and slide it into and through the ferruled cable housing.
  2. Run the cable and housing through the cable housing guide, and feed the cable through the shaft cross pin on the rocker lever . Seat the ferruled housing end into the remote cable hanger.
  3. With the housing ferrules firmly seated at both ends, tighten the cable fixing screw to 12 in-lb (1.4 N-m) torque.
  4. Allow about 1.25” (30 mm) cable excess before cutting and capping the cable end.
  5. With needle nose pliers, grasp the cable end just above where it exits the rocker lever and bend it towards the seatpost center, to about a 45 degree angle .
  1. Place the lower saddle clamp on the upper seatpost , making sure the stamped arrows point forward and the capped cable end feeds through the side opening of the lower saddle clamp.

    NOTE:  The FOX D.O.S.S. adjustable height seatpost can be used with saddles having 7 mm round rails or 7 x 9 mm obround or elliptical carbon rails; it cannot be used with saddles having 8 mm round rails.

  2. Place the upper saddle clamp with its stamped arrows pointing forward on top of the saddle rails, and set the saddle with upper clamp over the lower saddle clamp. Install the two saddle clamp bolts with spherical washers and barrel nuts, to fasten the saddle.

    NOTE:  Make sure the capped remote cable end does not get accidentally caught between the saddle rails and the saddle clamps.

  1. After confirming your final saddle level and fore/aft position, tighten the saddle clamp bolts to 60 in-lb (6.78 N-m) torque.
  2. Loosely fasten the cable housing to your frame with the provided zip ties. Drop the seatpost into Descend mode, noting the cable housing clearance with your rear tire. Slide the cable housing forward enough to achieve safe clearance, before fully tightening the zip ties.
  3. Thoroughly inspect and test your installation!

    WARNING:  Do not ignore these final steps of the installation procedure! Failure to ensure a proper and thorough installation can result in sudden failure, potentially causing SERIOUS INJURY OR DEATH.

    • Re-check remote cable clearances with the front and rear wheels, for all seatpost extension modes (Climb, Trail and Descend).
    • Check all bolts, fasteners for proper torque specification.
    • If you have an air rear shock: using a shock pump, measure and record the pressure reading in your rear shock. After releasing all air pressure from the main air chamber, inspect the cable housing, air chamber Schrader valve and saddle for clearance, in all seatpost extension modes, at full bottom-out of your shock. Restore your rear shock air chamber to its original PSI.
    • If you have a coil rear shock: remove the coil spring and inspect the cable housing, air chamber Schrader valve, and saddle for clearance, in all seatpost extension modes, at full bottom-out of your shock.

      TIP: For more information about removing the coil spring, visit http://www.ridefox.com, or contact FOX (1.800.369.7469 or mtbservice@ridefox.com).

Pneumatic Seatpost Return

The rate of full extension return is set by the amount of air pressure in the D.O.S.S. seatpost air chamber.

NOTE:  The FOX D.O.S.S. adjustable height seatpost comes pre-set with proper air pressure from the factory. If necessary, use the following procedure to adjust the pneumatic seatpost return rate.

CAUTION:  Be sure to always keep the Schrader valve end of the seatpost pointing upwards during this entire procedure. For best accuracy, use the FOX digital hand pump.

  1. Set the D.O.S.S. in Climb mode (full extension).
  2. While holding the seatpost with the air chamber Schrader valve pointing upwards, remove the air valve cap.
  3. Adjust the air pressure from a minimum of 10PSI for a gentle seatpost return to full extension, to a maximum of 25PSI for the quickest return rate.

    WARNING:  Never exceed 25PSI of air pressure in the D.O.S.S. seatpost air chamber. Excessive pressure could cause a sudden release from Descend mode, possibly causing you to lose control of your bicycle and sustain SERIOUS INJURY, OR DEATH.

  4. Reinstall the air chamber Schrader cap before installing the D.O.S.S. seatpost on your bicycle.

Maintenance Schedule

FOX products are racing quality components, constructed with precision parts having very close tolerances. Properly cleaning your FOX product between rides, in addition to maintenance service scheduled at regular intervals, will help to reduce repair costs and extend product life.

For further service procedures information, visit http://service.ridefox.com, or contact FOX for complete maintenance service (1.800.369.7469 or mtbservice@ridefox.com).

TIP: If the seatpost has not been used for an extended period, hang the bike upside down for several minutes to allow the internal oil bath to internally coat and lubricate the upper seatpost.

Each Ride Every Three (3) Months Every Twelve (12) Months
  • Clean the upper post with mild soap and water, and dry with a clean cloth. Inspect for any abrasion damage.
  • Test and verify smooth operation of complete D.O.S.S. remote lever and seatpost system.
  • Remove the seatpost from the bicycle and check the air pressure in the air chamber. Add air pressure as needed, preferably using a FOX digital air pump for best accuracy.
  • Lightly lubricate the outside of the upper post with FOX 10 wt green or similar suspension fluid. After cycling the seatpost a few times, wipe the upper post with a clean cloth.
  • Lubricate the remote cable.
  • Send to an authorized service center or FOX service for complete maintenance servicing.
  • Replace cable and housing.

Frequently Asked Questions

  • What is the air pressure range?

    10-25PSI, as measured with the seatpost set in Climb mode (fully extended). FOX recommends using the FOX digital hand pump to achieve best accuracy for setting the air pressure.

  • What are the torque values for the fasteners?
    • Saddle clamp bolts: 60 in-lb [6.8 N-m]
    • Remote lever bar mount clamp and pivot bolts: 15 in-lb [1.7 N-m]
    • Cable fixing screw: 12 in-lb [1.4 N-m]
  • Is it normal for some rotational play to occur between the upper and lower seatpost, when changing saddle height modes?

    Yes. The D.O.S.S. has a dual internal cam, anti-rotation mechanism that locks the seatpost rotationally when any one of the saddle height modes is engaged. This mechanism disengages, resulting in temporary rotational play only when the seatpost is in between any of the three saddle height modes. Once the next saddle height mode is reached, the anti-rotational mechanism is re-engaged, locking the seatpost into place with minimum rotation.

  • How should I transport my bicycle with the D.O.S.S.?

    Transport your bicycle with the D.O.S.S. in the lowest saddle height position (Descend mode), to prevent scratches or other abrasive damage to the upper seatpost.

Troubleshooting the D.O.S.S.

Issue Probable Cause(s) Solution(s)

The seatpost binds when changing saddle height mode.

Excessive torque applied to the seat tube collar binder bolt.

Do not over-tighten the seat tube collar binder bolt.

The seatpost is not staying in Descend mode.

  • Too much air pressure in the seatpost.
  • If recently serviced, too much internal lubricating oil might be present.
  • Make sure the pressure in the air chamber is not greater than 25PSI.
  • Make sure the amount of FOX Green 10 wt internal lubricating oil does not exceed 10 mL.

The seatpost is not staying in any saddle height mode.

  • Too much preload tension on the remote cable.
  • Remote cable housing interference.
  • Adjust remote cable tension with the cable adjuster until you achieve a small amount of free play with the long remote lever (1 to 2 clicks).
  • Re-check remote cable clearances with the frame and suspension movement, for all saddle height modes.

The seatpost is not fully returning, especially from Trail mode.

  • The seat tube collar is too tight.
  • There is not enough lubrication in main seal, causing excess friction.
  • Not enough air pressure in the seatpost (minimum 10PSI, maximum 25PSI).
  • The seatpost loses air pressure in a short time period.
  • Avoid overtightening the seat tube collar binder bolt.
  • Allow the internal oil bath to internally coat and lubricate the upper seatpost by hanging the bike upside down for several minutes.
  • Reset the air pressure to 10-25PSI.
  • If there is a leaking seal or a damaged upper seatpost, contact FOX or an authorized service center for repair.

The remote lever does not move.

The capped remote cable end is caught between the saddle rails and clamps.

Make sure the capped remote cable end is properly fed through the slot in the side of the lower clamp, and it does not get between the saddle rail and saddle clamps on the opposite side.

The seatpost does not move into Trail mode when the short lever is pressed, or does not move into Descend mode when the long lever is pressed.

Not enough preload tension on the remote cable.

Adjust your remote cable tension with the cable adjuster until you achieve a small amount of free play with the long remote lever (1 to 2 clicks).

The seatpost skips Trail mode and slips into Descend mode when the short lever is pressed.

Too much preload tension on the remote cable.

Adjust your remote cable tension with the cable adjuster until you achieve a small amount of free play with the long remote lever (1 to 2 clicks).

Converting the Remote Lever

To convert a left top-mounted travel lever assembly into a right top-mounted assembly (or vice versa):

  1. Loosen and remove the pivot bolt with a 3 mm hex key wrench.
  2. Insert the 3 mm hex key wrench into the vacant pivot bolt hole, to press and snap the pivot pin free.
  3. Keeping the levers within the remote lever housing , insert the pivot pin into the pivot hole on the opposite side of the lever housing, making sure the pivot pin cap fits into the slot in the lever housing.
  4. Insert the pivot bolt through one of three holes in the bar mount bracket .

    TIP: Use any of the three holes in the bar mount bracket to custom-set your reach adjustment for the remote lever assembly.

  5. Insert the pivot bolt with bar mount bracket into the remote levers to thread into the pivot pin, making sure the bracket fits into the slot in the lever housing.
  6. Tighten the pivot bolt with bar mount bracket into the pivot pin, to 15 in-lb (1.7 N-m) torque.

 


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