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Item # THP0020

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  • Black, 30.9 x 400 ($450.00)
  • Black, 31.6 x 400 ($450.00)
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Item # THP0020


It could only be Thomson.

Thomson has been on the move as of late, expanding from solely stems and seatposts to a complete line of handlebars. The biggest news, however, is the transition from static parts to its dynamic five-inch travel Dropper Seatpost.

The leap from expertly shaping alloy stems and seatposts to mastering hydraulics might seem like a giant one for a company to partake in but, keep in mind, Thomson has always been an aerospace contractor first, and cycling component manufacturer second. What this means is that Thomson has more then enough resources and design prowess to confidently enter the dropper post market, and a quick review of this seatpost brings that fact to light.

Thomson did have a head start over suspension-manufacturers entering this market with its classic two-bolt saddle clamping mechanism. Like the long-running Elite seatposts, the Dropper post has a one-piece, forged cradle that provides the same strength and durability that made the original a mountain biker's favorite. But, that's all that this adjustable saddle-perch shares with the original.

Smartly, Thomson outsourced the internals in order to decrease development time and to ensure reliability. This mechanism uses an oil cartridge to control height and a nitrogen shock to return it to full-height. It's controlled by a cable actuated handlebar remote that rotates a progressive cam, which opens the oil-passage valve between upper- and lower-chambers. Your weight forces the post down, and because oil doesn't compress, the post stays in whatever position it's in when you release the lever.

This makes the post infinitely adjustable, and the progressive cam ensures that the bottom doesn't instantly fall out. On the opposite end of the spectrum, a nitrogen shock pushes the saddle back up, and return speed is damped in the last 15mm of travel. So, you won't experience the ejector seat or 'slapper action of those early spring-loaded dropper posts.

The nitrogen shock also eliminates complicated air actuation by eliminating the need to bleed damage-prone hydraulic alternatives. Another key element to dropper posts is side-to-side play. Thomson addressed this with a keyed, four-section shape that prevents any saddle slop. The Dropper seatpost comes with a handlebar remote that's minimalist in design and machined from aluminum in true Thomson fashion. Thomson also gives the option of an under-saddle lever that's available separately.

The Thomson Dropper Seatpost is available in a 30.9 and 31.6mm diameter and in the color Black. It's overall length is 400mm, and it's important to note that it cannot be cut down. Additionally, the post has a 5mm offset.

Tech Specs

[seatpost] aluminum
30.9 mm, 31.6 mm
400 mm
Drop Range:
5 in, 125 mm
5 mm
Recommended Use:
mountain biking
Manufacturer Warranty:
2 years
Actual Weight:
Black, 31.6 x 400: 507g

Reviews & Community

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Thomson Dropper Seatpost

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Here's what others have to say...

4 5

Pretty good, slightly sticky.

  • Familiarity: I've used it several times

I bought my Thompson 125 dropper post to replace a KS LEV seatpost that was spending months away at KS for a standard rebuild. Sick of waiting and longing for the ability to lower my seat, I shelled out for the Thompson. In two months, it's been great. No discernible play up or down or side to side. The seat remains tight and I have not had to adjust anything since the initial install. My only qualms so far is that the last 1 cm of travel is sometimes sticky when the seat returns. It is usually the first 4-5 times I use the post in a ride, and I have to manually pull the seat back up to full extension. I've heard of this happening with other Thompsons. Right now it a 4 star post. The first rebuild will determine if the rating goes up or down.

Is this the v1 (short cable) or v2 elite...

Is this the v1 (short cable) or v2 elite dropper?

Responded on

It includes both sets of cables and housings. I have a large frame SC Tallboy and it small cable fit fine.

5 5

Best I've used so far

  • Familiarity: I've used it several times

While I haven't had this long enough to make a call on long-term reliability, I can say that it worked great out of the box, was easy to install, and has been flawless over the first month and ~200 trail miles in the PNW mud. Having used (and returned due to blown seals) a Reverb and KS Lev, this one has been the most pleasant user experience of the lot so far. The trigger feels great on the bar and fits well with shifter/brakes. Fingers crossed on reliability!

5 5

Beautiful piece of equipment

  • Gender: Male
  • Familiarity: I've put it through the wringer

Out of the box and installed without issue. Cable and housing length was spot on even for my XL Yeti ASR-7. Function is flawless so far and expect nothing but the best from Thomson. Will update as time goes on, but this is leaps and bounds better than my last dropper post.

4 months of use and still without an issue. I am also what most would consider a Clydesdale at 6'3" 240lbs geared up. I never have to think about it working or not working. If I don't have to think about a component, I consider it a win.

2 5

Play in the post after 1 month

  • Familiarity: I've used it several times

I'm 230 lbs, ~245 lbs with all my ride gear, and have been mountain biking for about two decades. Most of my riding in the past ten years falls into the all-mountain category. Out of the box, the Thompson post appeared promising. The post head makes saddle adjustments easy, and rock solid. Plus, the head/shaft machining is clean and bomber (I had problems on my old KS 950i post, where the saddle eventually spun on the seatpost shaft head). The handlebar lever is small, and required some trial and error to find the best ergo location on the handlebars. Strangely, Thompson shipped the post with a cable housing that was at least three inches too short for my frame (easily solved with spare housing I had on hand). Once installed, the seatpost adjusted easily, and had a rock-solid feel. Unfortunately, the post developed slop in the collar at the top of the fixed section of tubing (the part that stays inside the bike frame). After about a month of use, I could see several degrees of movement in the saddle and hear creaking during seated climbs. No post I've used so far has been perfect, but at this price, the Thompson shouldn't show this much wear in less than a season.

Responded on

I had the same problem. Called David at Thompson, he explained to me that the first run had a problem with this. He sent me a Newport and I have no problems since.