26.8mm seat posts weren't ever an overly popular size, and not are obsolete, which makes finding a dropper post for them extremely problematic. I found three options:
1. Gravity Dropper - The Gravity Dropper was one of the first dropper posts and is the only out-of-the-box solution for a 26.8mm dropper. There are some issues though. First, Gravity Dropper has seemingly gone out of business, so you'll be stuck trying to find a used one in a rare size. Second, the maximum travel for a 26.8mm version is 100mm. Third, because of the actuators location, they have a very high stack height. Finally, they have a large protective boot (their design requires it), but they are very robust seat posts and will last a very long time with maintenance.
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| The venerable OG dropper post. |
2. Modified 27.2 dropper - I took a 27.2mm dropper post with under-the-seat lever actuation and turned the body down to 26.8mm with my lathe, which meant reducing the wall thickness by 0.2mm. The only reason I'm comfortable running this post is because it's inserted all the way into the frame, and the post's collar is resting on top of the seat post clamp. This means the entirety of the turned down body is containing within the seat tube of the frame, making the loss of strength a non-issue.
The post has 125mm of travel, which is the height I needed for this specific bike.
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| Turning the seatpost body down from 27.2 to 26.8 on the lathe. |
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| Reassembled. |
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| Installed on the up position. Note the dropper collar is sitting on the seatpost clamp |
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| Installed in the down position. |
3. Modified DT Swiss D232 dropper - The DT Swiss D232 dropper only has 60mm of travel, but is notable because the entire dropper mechanism is contained with the top part of the seat post, making it possible to cut the top off right where the stanchion starts, and transplant it to a seat post diameter and length of your choosing. This is the only dropper option for my bike with an interrupted seat tube that's only 160mm long.
Because the activation mechanism is house in the top of the seat post, with a little bit of work you can have the cable enter the seat post pretty much anywhere below the stanchion.
In my case I cut the stanchion off the D232 (make sure to cut it below where the wiper sits in the down position), then I machined a new 26.8mm seat post body, and pressed the stanchion onto the new seat post with a helping of Loctite retaining compound. From there, it was simply a matter of routing the cable and reassembling it.
Notes:
- Because of the design, there must be a minimum of 200mm of seat post exposed. If you modify the D232 mast to accept a OneUp seat clamp, that can be dropped to 190mm of seat post exposed.
- The activation spoke (yes, it's literally a spoke) can be removed and the dropper cable run directly through the activation piston. This just requires a way to terminate the cable house at the bottom of the post, which can easily be accomplished via either 3D printing or modifying the existing bottom cap.
- The spring guide is glued into the top of the slider tube. If you remove it, you'll need to use VHB tape to reattach it after a thorough cleaning.
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| D232 disassembled. |
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| Turning the new 26.8 seatpost body on the lathe. |
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| The D232 stanchion press fit on the new 26.8 body. It's a 0.02mm interference fit. |
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| Installed on the bike and in the up position. I decided to make things harder for myself and routed the dropper cable through the frame's seat post clamp. |
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| Installed on the bike and in the down position. |
