Thomson Elite Dropper Service Guide- Mtbr.com
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  1. #1
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    Thomson Elite Dropper Service Guide

    Hi, this is my guide to striping and servicing a Thomson Dropper.

    I have some more pictures but can only upload 5 per post so I've used these to show and overview and some finer points.

    I'm posting this as I spent a long time trying to find some information on them and other than a £170 "cartridge replacement service" I was out of options.
    My issues was when under load the post would squish/drop slightly but other wise functional. Its been used for 4 years without issue and is a beautifully made post so wanted to keep it.
    Given the lack of data I had to assume certain information so this is very much how I serviced it and not a factory procedure.
    I also assume you know how to use tools properly and use appropriate clamps for tubes etc so some of the steps may seem brief or not specific in areas, just ask for finer points if required.

    Tools that I used:
    3/8 ratchet
    15mm socket
    5mm socket (on a 1/4 ratchet or screwdriver)
    Needle nose pliers
    Valve core tool with a long shaft
    Park Tool AV-5 clamps
    T10 Torx (possibly T8, sorry i forget)
    Strap Wrench
    1mm allen key
    Rockshox Monarch/Super Deluxe air valve adapter

    I used 10wt fork fluid, no good reason other than I had plenty and didn't want to waste the more expensive damper fluid (3wt) I have or Fox Gold 20wt (please please don't use Gold 20wt!)
    A clean syringe and a length of tube will be very helpful.

    Step 1:
    Loosen the 1mm grub screw in collar then loosen the collar with a strap wrench.

    Step 2:
    Remove the red cable push/pull system from the base, it unscrews by hand easily, otherwise use the strap wrench. You can now see what I highlighted as the Actuator.
    In the centre you'll see a small (I think 5mm) bolt cap, unscrew this to reveal the airvalve. depress the air and remove the valve core.

    Fully unscrew the top and bottom of the cartridge (15mm hex) and lower the seatpost stanchion to reveal the top of the cartridge. Invert the whole seatpost and clamp the top of the cartridge in the vice (I used the Park Tool AV-5 for all the clamping). Now loosen the top cap (remember seatpost is upside down so the bottom as you look at it) but don't unscrew fully.
    Now turn the post up the right way and remove cap, you can now tip out the oil and slide the cartridge out of the seatpost.

    Step 3:
    The seatpost itself can now be service and I would advise this before moving onto the cartridge, it will be apparent why later.
    This is quite a simple thing, simply unscrew the collar fuller and the post comes apart, stripe/clean/grease as needed. I would check the key way bush screws are tight, the ones on mine were all loose. I used a small drop of loctite and a T6 torx to refit.
    I used a suspension grease for lubrication but a general grease will probably be fine.
    The seatpost can be fully reassembled and left for now.

    Step 4:
    You can now disassemble the cartridge. The upper (longer) tube I refer to as the Fluid Reservoir and the lower (shorter) as IFP Canister.
    Clamp the reservoir and unscrew the piston band cap.
    There will be a small amount of oil in the shaft and IFP canister.
    Clamp the IFP canister and unscrew the bottom cap and then the top cap. Slide the top cap right up and you'll be left with the IFP left in the canister. Gentle push this DOWNWARDS with something blunt that wont scratch the inside of the IFP or shaft.
    Carefully remove the o-rings and seals, take a picture so you can reference the orientation of seals and support rings etc.
    Undo the Flow Valve, see the picture.

    Step 5:
    Clean everything.

    Step 6:
    Rebuild time. I'm still perplexed as to how the factory actually do this but this is how I did it with relative ease and success.
    At this point leave the flow valve removed. Lightly grease the reservoir piston seal and orings then tighten the reservoir to the piston band cap.
    Lightly grease the seals for the IFP and canister, lower the IFP to the bottom of the shaft (this is important) and slide the canister over it then tighten bottom cap.
    Clamp upright in a vice for ease of work and half fill the reservoir and IFP canister with fluid. It will drain down the shaft and into the canister and help bleeding. As the canister fills up allow it to overflow and then tighten the cap (as per picture).

    Step 7:
    With the reservoir fully extended half fill then lower the tube until level with the oil. Place your thumb over the top creating a seal and extend the shaft. This creates a vacuum and draws the air to the top, hold the shaft extended for a few seconds and repeat a few times.
    Now you need to lower the tube whilst keeping the oil level above the flow valve seat. Lower the tube slowly and keep an eye on the oil level, if necessary wrap the tube with a rag and allow the oil to over flow.
    So no you have the IFP canister filled and bled and the reservoir tube in its lowest position (think fully dropped) with oil up to the top.
    Its a bit tricky now but refit the flow valve remembering to gentle hold the actuator to stop it rotating.
    Now fit the top cap to the reservoir tube and "nip" it up, its being removed in a minute so not tight.

    So the finer points for this procedure above- The IFP needs to be at the lowest point to allow for the maximum displacement because the cartridge is assembled in the fully dropped position. I also don't know what the set height should be (normally around 2/3 of canister volume) so allowing for maximum displacement means it wont hydraulic lock.
    Also as it happens you can only refit the flow valve (easily) whilst the cartridge is in the fully dropped position. The reason the flow valve is fitted last is because it literally stops fluid passing, you cant lower the reservoir tube with it in place WITHOUT pressing down on the actuator which is very tricky at this point.

    Step 8:
    Refit the valve core and put approx 100psi in using the Rockshox air valve adapter. I had to borrow the o-ring from the actuator/airvalve cap as the Rockshox adapter o-ring is just to small to seal fully.
    Fit the cap (minus the o-ring at this point). You now need to depress the actuator by pushing on the cap quite firmly. I used the handle of a small screwdriver.
    When depressed you need to fully extend the cartridge, the airpressure might not be enough so just pull it up with your other hand. Leaving the cartridge still clamped in the vice will help as a third hand here.
    Once fully extended remove the cap and depressurise, i would recommend removing the valve core to be 100%.

    Step 9:
    Almost there!
    Now you have a service seatpost (fully reassembled) and a cartridge ready to be fitted. Make sure there is a good amount of grease on the piston band now.
    You maybe wondering how the cartridge goes back in as both the top and bottom need to be screwed back into the top and bottom of the seatpost. Ill be honest and say this took me a few goes and head scratching to figure out solving one issue at a time.

    Take your now fully extended cartridge and carefully unscrew the top cap, holding upright slide it back through the seatpost (seatpost in fully dropped position) and gentle screw back into the bottom of the post. The cartridge now sticks out the top.
    top up the fluid and screw the top cap back on, 99% of the air will push out past the threads so just tighten slowly.
    You can now clamp the reservoir back in the vice to fully tighten the top cap.
    Finally slide the seatpost up and tighten the top. Refit the valve core and pressurise, i went to 200psi. replace the "borrowed" o-ring and valve cap.
    All things being well you should now have a lovely, clean, fully functioning seatpost.

    One side note, if you had damaged seals or there was alot of leaked fluid you'll obviously need to find replacement seals, I'm sorry I don't have any specs for these to hand.

    I have some more pictures I can post that show some parts in greater details. I think I remembered all the important bits, if you want me to fill in the gaps or help please ask.

    Rich.
    Attached Thumbnails Attached Thumbnails Thomson Elite Dropper Service Guide-2f4ef0e1-bf1b-43b6-a0aa-58a3f8d46d9a.jpg  

    Thomson Elite Dropper Service Guide-115d9ca3-5efe-4f32-b07c-1c4e30b29579.jpg  

    Thomson Elite Dropper Service Guide-bb78bef8-248a-4d6c-8d92-dddd2086d350.jpg  

    Thomson Elite Dropper Service Guide-c2dd1f88-b3b9-467a-8719-a857b0f18adc.jpg  

    Thomson Elite Dropper Service Guide-94ef9b51-3129-4b1b-8178-4226bb353f74.jpg  


  2. #2
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    I just want to say THANK YOU for this post (pun sort of intended). I bought a used Thomson post and given the super low price, I knew something had to be up with it, despite being assured that it was in "perfect working condition". Sure enough, it arrived and it had so much squishiness to it just holding in my hands that I never even attempted to install it. I immediately followed your guide to servicing it. I ran into a few snags, but eventually everything worked out and now it functions flawlessly. There are a couple of points I want to address in the procedure that ended up being a bit tricky for me and feel like having a heads up before hand could save someone some headache. One is that the 15mm socket that you need should be a relatively thin walled 6 sided socket (the kind with flats for each side. I initially tried to use the star sockets that are in my set and they simply don't work even if they are the right size). Next, there is a little black cap on the side of the post near the seat clamp that is secured in place with a tiny set screw. This needs to be removed in order to unthread the top cap. I didn't remove it initially and could not figure out why I couldn't get the top cap off and then realized that the threads were contacting the cap on the inside of the post. Lastly, it took me forever to figure out how to air up the post. First, I did not have the Rockshox air adapter so when I got to that point, I had to pause, order it on Amazon and wait for it to come before finishing. There really is no way to do it without that little $10 piece. Next, even with the adapter, I could not get it to retain air after unscrewing my shock pump. I ended up having to drill out the inside of the adapter to allow the schrader pin to close and not contact the adapter. And by drill out, I mean literally hold a drill bit in a set of pliers and rotate the adapter by hand. It is soft aluminum and I didn't need to take off much so didn't want to risk using a drill. Other than that, everything else was pretty straight forward. This definitely takes some patience but also saves the hassle and the close to $200 for sending it off to Thomson for a service

  3. #3
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    Glad it helped, thanks for the points you made. It took about a week for MTBR to authorise my account to post so I wrote the article quite a awhile after.
    Forgot about the external lever blank on the top of the post, I missed that the first time as well.
    Secondly it didnít occur to me but Iíd already enlarged the hole on my RS air valve adapter because of that very problem when servicing my Super Deluxe. Pretty sure these arenít made right in the first place.
    Itís abit of a fiddle but like you say itís not to bad and nice to actually service it yourself. Might look for some cheap ones to buy and sell on 😁

  4. #4
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    Thanks Wild_Richie for the very in-depth instructions. My Thompson Covert is going on five years old and has had one rebuild two years ago so I am expecting it to require another one in the not too distant future. This thread will be a great resource if I decide to tackle it myself.

  5. #5
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    do you have any images of the covert base cap?? buddy of mine has his in bits and can't fathom how it goes back together, i cant get my head around the parts he has and how it should work!!
    I am the biketart!

  6. #6
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    Iíll take a picture of it and post for you 👍🏻

  7. #7
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    Thanks for this, very useful. I'm in the middle of my seatpost but its an external cable not internal. Everything is upside down i.e. the air valve is in the top under the seat clamp and the bottom of the cartridge is held in place with a curious triangular bolt. I dremmeled a 6mm socket to fit this. The top of the cartridge is held in with a 14mm hex bolt under the seat clamp. I used a single hex socket ground down flush as the hex is alloy and quite shallow.

    The cartridge is also effectively upside down i.e. the shorter section is on top and the longer at the bottom. Not sure to take this apart or not as it was more or less working fine (occasionally sags by about 3mm) I took it apart due to lots of rock and horrible noises coming from it (many creaks and cracks) Like yours the wee screws on all three keyway bushings were loose and there wasn't much grease in it.

  8. #8
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    Quote Originally Posted by HT5rider View Post
    Thanks for this, very useful. I'm in the middle of my seatpost but its an external cable not internal. Everything is upside down i.e. the air valve is in the top under the seat clamp and the bottom of the cartridge is held in place with a curious triangular bolt. I dremmeled a 6mm socket to fit this. The top of the cartridge is held in with a 14mm hex bolt under the seat clamp. I used a single hex socket ground down flush as the hex is alloy and quite shallow.

    The cartridge is also effectively upside down i.e. the shorter section is on top and the longer at the bottom. Not sure to take this apart or not as it was more or less working fine (occasionally sags by about 3mm) I took it apart due to lots of rock and horrible noises coming from it (many creaks and cracks) Like yours the wee screws on all three keyway bushings were loose and there wasn't much grease in it.
    Did you ever finish the rebuild of your Elite dropper with external cable? I have the same dropper, and really only need to inspect the bushings because they are making a horrible creaking noise when the post is fully extended. I was curious if you ran into any other unique issues compared to the OP.

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