2018+ Transfer Seatpost Rebuild (Internal)
- 019-01-083 Fastener, Standard (Metric): Screw [M3 X 16mm] SHCS, Patchlock (QTY: 2 for Sealhead removal)
- 398-00-690 Service Tool, IFP Height, 1.870 (150mm Travel)
- 398-00-691 Service Tool, IFP Height, 1.990 (100/125mm Travel)
- 398-00-700 Service Tool, Internal Spool Valve Compressor Knob, Transfer
- 398-00-735 Service Tool: Open Valve, Nitrogen Fill, Transfer
- 398-00-737 Service Tool: Funnel, Spool Valve, Transfer
- 398-00-738 Service Tool: Bullet, 8mm Shaft, Transfer
- 398-00-739 Service Tool: Cap Removal, Transfer
- 398-00-740 Service Tool: Push Rod, Delrin, Transfer
- 398-00-758 Service Tool: Support, Gas Fill
- 803-00-147 Kit: Shaft Clamps, 07 FORX, Set #2 (32 X Body, 36, 40 Forx)
- 803-01-127 Service Tooling: Upper Bushing Removal, Transfer
- 803-01-200 Kit: Service Tool, 2018 Transfer, Upper Bushing and Seal Installer
- 803-01-384 Service Tool: Gas Fill, 100-175mm Transfer, Assy
WARNING: Do not unthread the 6mm hex at the top of the seatpost (beneath the saddle clamps) until after you have released the IFP pressure from post as shown in disassembly step 10. Failure to properly release IFP pressure before unthreading the 6mm hex can lead to oil escaping at high pressure which may cause SERIOUS INJURY OR DEATH.
WARNING: FOX products should be serviced by a qualified bicycle service technician, in accordance with FOX specifications. If you have any doubt whether or not you can properly service your FOX product, then DO NOT attempt it. Improperly serviced products can fail, causing the rider to lose control resulting in SERIOUS INJURY OR DEATH.
WARNING: Modification, improper service, or use of aftermarket replacement parts with FOX forks, shocks, and seatposts may cause the product to malfunction, resulting in SERIOUS INJURY OR DEATH. DO NOT modify any part of a fork, shock, or seatpost including the fork brace (lower leg cross brace), crown, steerer, upper and lower leg tubes, or internal parts, except as instructed herein. Any unauthorized modification may void the warranty, and may cause failure or the fork or shock, resulting in SERIOUS INJURY OR DEATH.
WARNING: FOX products contain pressurized nitrogen, air, oil, or all 3. Misuse can cause property damage, SERIOUS INJURY OR DEATH. DO NOT puncture, incinerate or crush any portion of a FOX product. DO NOT attempt to disassemble any portion of a FOX product, unless expressly instructed to do so by the applicable FOX technical documentation, and then ONLY while strictly adhering to all FOX insturctions and warnings in that instance.
Some images within this rebuild procedure show parts from a 2017 Internally Routed Transfer Seatpost. While these 2017 Internal Seatpost parts may appear different than those used in the 2018 Internally Routed Transfer Seatpost, the information and steps presented will guide you through rebuilding the 2018 Internally Routed Transfer Seatpost.
Transfer Seatpost Model Year Identification
You can determine the model year of your Transfer Seatpost by checking the part number against the table below. Transfer Seatposts have their part number etched into the Bottm Cap Assembly at the very bottom end of the outer post.
|2017 Transfer Seatposts||Part number range|
|925-00-033 through 925-00-058|
|925-01-030 through 925-01-053|
|925-02-001 through 925-02-037|
|2018 Transfer Seatposts||Part number range|
|925-00-070 through 925-00-095|
|925-02-100 through 925-02-127|
The following procedure guides you through the full rebuild of the 2018+ Transfer Seatpost with Internal Cable Routing. The 2017 Transfer Seatposts with Internal Routing are slightly different from the 2018 models and can be rebuilt using the instructions found here: 2017 Transfer Seatpost Rebuild (Internal) »
Additional part information and drawings for the 2018 Transfer Seatpost can be found at: Transfer Seatpost »
Cross Section Drawings and Index Pin Information
The brass Index Pins used in the Transfer Seatpost must be replaced on each rebuild and are not part of the rebuild kit. You must order Index Pins individually to meet the needs of the Transfer Seatpost being rebuilt.
Below are some cross section drawings that may be helpful to understand the complete assembly of the seatpost.
Contamination or damage to the Pressure Relief Valve Assembly can cause an oil leak that allows the post to travel up when unweighted and down when weighted by a rider without actuation of the remote lever.
If experiencing these conditions, please replace the original Pressure Relief Valve Assembly as shown in the rebuild instructions below.
Clean your bike work stand clamps and the exterior of the seatpost to prevent damage during clamping. Remove all saddle hardware and set aside. Clamp the upper post horizontally by the head in your bike work stand so that the post cannot rotate.
Unthread the Bottom Cap counter clockwise while holding it by it's thickest section to remove it from the lower post.
Slide the Lower Post up to expose the Shaft and Shaft Lug. Take note of the position of the ball bearing and mark the anti-rotation hole that the ball bearing was found in.
If you use a Sharpie or other marker to make this mark, take care not to remove the mark as you clean parts throughout the rebuild. A scribed line is also an option for marking the position of the ball bearing.
Remove the 2mm ball bearing and set it aside in a protected location as it is small and easy to lose.
Carefully clamp the Shaft in your shaft clamps (PN: 803-00-147) using proper shaft clamp techniques to prevent damage to the sealing surface, then unthread the Shaft Lug counter clockwise with a 10mm wrench to remove it. Remove the original bottom out bumper.
Carefully insert the Upper Bushing Removal Tool (PN: 803-01-127 with 398-00-544 for 175mm posts) into the Lower Post with the plastic end first. Insert the tool far enough to allow the nut with flat sides to enter the lower post. Reinstall the wire retaining ring into the Lower Post to capture the nut as shown.
Hold the 22mm wrench flats and slowly thread the tool into the post clockwise with a 15mm socket to push out the Upper Bushing and Wiper Seal.
Pull the Upper Post from the Lower Post to separate. Keep the post low over your bench to prevent the 3 brass Index Pins from getting lost. Remove the Upper Bushing Removal tool by pulling it out from the top of the Lower Post.
Clamp the Upper Post in your bike work stand, then slowly unthread the bleed screw to release IFP pressure. Remove the screw from the Sealhead with a 1.5mm hex wrench. The bleed screw is the M3 screw that is farthest from the blind hole in the Sealhead. Make sure that all pressure is released before moving on to the next step. Remove the 0.083" ball bearing from beneath the bleed screw. A magnet may be necessary for removal.
Remove the fill screw from the Sealhead with a 1.5mm hex wrench. The fill screw is the M3 screw closest to the blind hole in the Sealhead. Remove the 0.083" ball bearing from beneath the bleed screw.
Remove the anti-tamper pellet from the Spool Valve Cap. With the Upper Post clamped vertically in your bike work stand, hold the Spool Valve Cap with your pin spanner, then unthread (counter-clockwise) and remove the M6 screw with a 4mm hex wrench. Remove the o-ring from beneath the M6 screw.
Slowly press the Spool Valve Cap down into the Upper Post to make room to access the wire retaining ring. Oil will spray out at this point. It is recommended to cover the post with a lint-free paper towel before doing this step. No paper towel is shown in order to illustrate the step more clearly.
Thread the Spool Valve Cap Removal tool (PN: 398-00-739) clockwise into the Spool Valve and pull up to remove. Replace the o-ring on the Spool Valve Cap with a new greased one from the kit then set aside.
Pour the oil out through the top of the post into your waste oil basin. Push the Piston Assembly out through the top of the Upper Post with a wooden dowel.
Clamp the Upper Post in your bike work stand with the bottom end facing up. Push the Sealhead in to make room to access the wire retaining ring. Use a shim to remove the wire retaining ring. Set the ring aside.
Thread an M3 screw into both the fill and bleed ports of the Sealhead. Screw 019-01-083 may be used for this. Lift up on both screws to remove the Sealhead from the Upper Post. Replace the Sealhead o-rings with new greased ones from the kit.
Insert the Delrin Push Rod (PN: 398-00-740) into the top of the Upper Post, then push the IFP out through the bottom. Replace both IFP seals with new greased ones from the kit.
Carefully clamp the shaft in your shaft clamps, then hold the base of the piston to prevent it from unthreading. Slowly unthread (counter-clockwise) the Pressure Relief Valve Assembly as it is spring loaded. Use an 8mm wrench to remove the assembly and set it aside. Remove the crushwasher, spring, and the 3/16" ball bearing and set them aside. The ball bearing may need to be removed with a magnet or shaken out after removing the Spool Valve Assembly.
A box-end wrench is shown in this step for clarity. FOX recommends the use of a 8mm 6-point socket.
Push up on the Push Rod to drive the Spool Valve Assembly out through the top of the Piston. You can use a small hex wrench to help push the Spool Valve Assembly far enough to grab it and continue removal by pulling from the top.
With the Shaft clamped, grab the base of the piston and remove it by unthreading counter clockwise. There are no wrench flats on this part, so be careful not to use more clamping force than is required to loosen the part.
Grab the Push Rod above the o-ring and hold it from turning while you unthread the Spool Valve with a 7mm wrench.
Holding the Push Rod below the o-ring stresses the small cross section area at the o-ring gland and can cause damage to the part.
Prepare the new Spool Valve Assembly from the kit by coating it in a thin film of Slick Honey and passing it through the Funnel tool to size the glide rings.
While holding the Push Rod above the o-ring, install the new Spool Valve Assembly from the kit onto the Push Rod and tighten clockwise to 15 in-lb (1.7 Nm) torque.
Holding the Push Rod below the o-ring stresses the small cross section area at the o-ring gland and can cause damage to the part.
Locate the indicator groove on one end of the Shaft, then install the Piston onto that end of the Shaft. Tighten clockwise until hand tight.
Carefully clamp the shaft in your shaft clamps with the Piston oriented up, then install the Spool Valve Funnel tool (PN: 398-00-737) onto the Piston.
Coat the Spool Valve Assembly with a thin film of Slick Honey, then install it into the Piston through the Funnel tool as shown. You can use a wooden dowel to push the Spool Valve Assembly fully into the Piston. Remove the Funnel tool.
The Funnel tool is also a sizer for the glind bands and may necessitate the use of additional force to push the Spool Valve Assembly through.
Drop the 3/16" ball bearing into the Piston Assembly followed by the Spring. Place the new crushwasher from the kit onto the Piston making sure to orient it with its counterbore facing the piston as shown.
Push down with the Pressure Relief Valve Assembly to compress the spring as you thread the Pressure Relief Valve Assembly in clockwise. Tighten to 40 in-lb (4.5 Nm) torque with an 8mm socket.
Check that all components are assembled correctly by pressing the Push Rod against the bench. It should be spring loaded and return when released. If this does not happen, replace the Spool Valve Assembly.
Coat the first 2 inches of the inside of the Upper Post with a thin film of Slick Honey, making sure to fill the retaining ring grooves. Install the IFP into the Upper Post as shown. Push the IFP into the Upper Post with your finger until it bottoms out to make room to install the retaining ring.
Carefully install the wire retaining ring into the deeper of the two grooves in the bottom of the Upper Post. Do not scratch the inside of the post with the open end of the wire retaining ring as the sealhead must seal against the surface that the wire retaining ring passes.
Install the 8mm Shaft Bullet (PN: 398-00-738) onto the end of the Shaft, then coat it with a thin film of Slick Honey. Install the Piston Assembly into the top of the Upper Post with the greased bullet first. Push the assembly into the Upper Post until you seat the seals on the Piston inside the Upper Post. Remove the bullet tool.
Extend the Piston Assembly up out of the top of the Upper Post just until you have clearance to add oil beneath it into the post. Do not allow the shaft to pull free from the IFP. Add FOX 1.5wt oil into the Upper Post, just under the Piston Assembly, until as full as possible.
Slowly push the Piston Assembly into the top of the Upper Post until the Shaft extends out from the bottom of the Upper Post. Oil may spray out at the piston. It is recommended to cover the post with a lint-free paper towel before doing this step. No paper towel is shown in order to illustrate the step more clearly.
Pour FOX 1.5wt oil into the Upper Post above the Piston Assembly until full. Thread the Shaft Lug onto the Shaft and tighten until hand tight. Install the Internal Spool Valve Compressor tool (PN: 398-00-700) into the Shaft Lug, threading clockwise until hand tight.
Keep the post vertical and slowly cycle the Shaft fully up and down 5-7 times while watching for bubbles at the top of the Upper Post.
When no new bubbles appear while cycling the Shaft, fully extend the Shaft and remove the Shaft Lug with the Internal Spool Valve Compressor tool. Install the appropriate IFP Height tool for your post, then reinstall the Shaft Lug with the Internal Spool Valve Compressor tool.
|Transfer Travel||IFP Tool|
Hold the Shaft at full extention while you insert the IFP tool up into the bottom of the Upper Post until it bottoms out. Remove the Shaft Lug with the Internal Spool Valve Compressor tool and the IFP tool.
Hold the Shaft at full extension, then compress and hold the Push Rod in for 5-7 seconds approximately 5-7 times to release any trapped air within the system.
Drop the Spool Valve Cap into the top of the Upper Post, then press it down to seat. Oil will spray out at this point. It is recommended to cover the post with a lint-free paper towel before doing this step.
Install the wire retaining ring above the Spool Valve Cap, then thread the Spool Valve Cap Removal tool and pull up to seat the Cap. Remove the tool.
Make sure that the Spool Valve Cap is topped off with oil. Install a new o-ring from the kit into the Spool Valve Cap followed by the M6 screw. Do not attempt to install the o-ring onto the M6 screw as it will not seat properly. Hold the Spool Valve Cap with your pin spanner white tightening the M6 screw with a 4mm hex wrench clockwise to 30 in-lb (3.4 Nm). Install a new anti-tamper plug from the kit into the hex of the Spool Valve Cap.
NOTE: Spool Valve Cap Removal Tool (PN: 398-00-739) may be used to press in the anti-tamper plug.
Add 0.5-1cc of Float Fluid to the IFP chamber. Install the 8mm Shaft Bullet tool onto the shaft and coat it with a thin film of Slick Honey.
Install the Sealhead onto the Shaft with its flat side facing the Upper Post. Remove the Bullet tool, then use the IFP tool to push the Sealhead into the Upper Post as far as it will go.
Install the 0.083" ball bearing into the bleed hole, apply blue Loctite 242 onto the M3 set screw, then install the set screw. Install an M3 screw in the fill port and hold it to prevent Sealhead rotation while you tighten to 8 in-lb (0.9 Nm) torque with a 1.5mm hex wrench. The bleed screw is the M3 screw that is farthest from the blind hole in the Sealhead.
Install the Nitrogen Fill Open Valve tool (PN: 398-00-735) onto the end of the Shaft. Install the Gas Fill Assembly (PN: 803-01-132) into the fill port. Be careful not to scratch the shaft as you install and use the Gas Fill Assembly. Hold the Shaft to help you tighten the Gas Fill Assembly into the fill port fully. Use the Gas Fill Support Tool (PN: 398-00-758) or wrap a small piece of tape around the Shaft and Gas Fill Assembly to add support and prevent damage to the Gas Fill Assembly.
NOTE: The Gas Fill Assembly (PN: 803-01-132) can be used with a High Pressure Shock Pump if needed. The following steps show the use of a Nitrogen system which is the prefered method.
Install the Gas Fill Assembly onto your Nitrogen system, then support the seatpost so it does not rely on the Gas Fill Assembly. The Gas Fill Assembly can be damaged if used to support the weight of the seatpost.
The Transfer IFP chamber must be filled to 275psi/18.9 bar (100mm, 125mm, and 150mm travels) or 325psi/22.4 bar (175mm travel posts) very slowly so you do not damage the Nitrogen fill check system within the Sealhead. Charging the IFP chamber too quickly can damage the Sealhead assembly.
Set your regulator to 0psi (0 bar) and slowly increase pressure over the course of 30 seconds until you reach the appropriate pressure:
|100mm, 125mm, and 150mm posts||275psi (18.9 bar)|
|175mm posts||325psi (22.4 bar)|
Remove the tape and Gas Fill Assembly from the Sealhead. Remove the Nitrogen Fill Open Valve tool. Install the 0.083" ball bearing into the fill hole, apply blue Loctite 242 onto the M3 set screw, then install the set screw. Tighten to 8 in-lb (0.9 Nm) torque with a 1.5mm hex wrench. Check that both the fill and bleed screws are properly tightened to 8 in-lb (0.9 Nm) torque.
Temporarily install the Lower Bushing, then install the new Wiper Seal from the kit. Remove the Lower Bushing.
Install the new Upper Bushing from the kit with its "crown-shaped" portion oriented toward the top of the post. Install the new o-ring from the kit onto the upper post followed by the new Lower Bushing.
Install the new bottom out bumper from the kit onto the Shaft lug then thread the Shaft Lug onto the Shaft clockwise. Clamp the Shaft, then tighten the Shaft Lug onto the Shaft to 30 in-lb (3.4 Nm) torque with your 10mm wrench.
Note: Some images show MY17 post without bumper. Bumper should be installed for all MY18 posts and MY17-MY18 conversions.
Fill the Index Pin slots with Slick Honey, then install replacement Index Pins. Note the number of indicator marks on the Index Pins to replace with pins of the same specification as those that came out of the seatpost. If the seatpost was experiencing play, you may replace the original Index Pins with pins having one additional indicator mark. You may only need to increase pin size for 1 of the 3 pins to eliminate play. Never increase to pins having 2 or more indicator marks than the original pins.
Install the anti-rotation 2mm ball bearing into the pocket on the Shaft Lug that you marked during disassembly. The marked pocket should align with the saddle clamp and the Index Pin that is farthest from the other two.
Note: MY17 post shown, MY18 post would have the bumper on the shaft lug.
Align the anti-rotation ball bearing with the groove in the inside of the Lower Post that is inline with the laser etching on the back of the Lower Post. Slowly feed the Upper Post Assembly into the Lower Post. Make sure that the wire retaining ring is still present in the Lower Post after having reinstalled it in disassembly step 6. Without the wire retaining ring in place, the Shaft Lug can go beyond the end of the Lower Post.
Note: Increased force may be required to install the upper post into the lower post as the lower bushing is now energized by the new o-ring.
Thread the Bottom Cap into the end of the Lower Post. Clamp the upper post horizontally by the head in your bike work stand so that the post cannot rotate. Tighten the Bottom Cap clockwise using its thickest part to 40 in-lb (4.5 Nm) torque.
Loosely position the Upper Post upside down in the Upper Bushing and Seal Installer (PN: 803-01-200) so the Upper Bushing rests on the tool. Push the Lower Post down against the tool to install the Upper Bushing.
NOTE: Post is shown with MY17 bushing installation technique using shaft clamps, New MY18 bushing install uses the new tool (803-01-200) which is shown in last image of this step.
Start seating the Wiper Seal by hand, then use your Upper Bushing and Seal Installer to fully seat the Wiper Seal.
NOTE: Post is shown with MY17 wiper installation technique using shaft clamps, New MY18 wiper install uses the new tool (803-01-200) which is shown in last image of this step.
Test that the seatpost functions properly by actuating the rocker lever and compressing the post against your work bench. Clean the exterior of your Transfer Seatpost before reinstalling it onto the bike.