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ThomsonDropper Seatpost


Item # THP0020

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  • Black, 30.9x375mm/100mm Travel ($450.00)
  • Black, 30.9x400mm/125mm Travel ($450.00)
  • Black, 31.6x375mm/100mm Travel ($450.00)
  • Black, 31.6x400mm/125mm Travel ($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.

  • Classic Thomson saddle clamp
  • Oil cartridge
  • Nitrogen shock
  • Infinite adjustability
  • Top 15mm of travel is damped
  • Handlebar remote and under-seat lever included

Tech Specs
Material[seatpost] aluminum
Diameter30.9mm, 31.6mm
Recommended Usemountain biking
Manufacturer Warranty2 years

Actual Weight

Actual weights are measured in-house by the Competitive Cyclist team.

Have questions? Chat with a Gearhead



Black, 30.9x375mm/100mm Travel
Black, 30.9x400mm/125mm Travel
Black, 31.6x375mm/100mm Travel
Black, 31.6x400mm/125mm Travel

View more Dropper Seatposts

    What do you think about this product?


    >Rating: 5

    Thomson knows their stuff

    I've put it through the wringer

    I rode this dropper hard for several years on a Santa Cruz Tallboy and it never let me down...or, more accurately, it always let me down when I needed it to and always came back up again when needed! I've since handed this bike down to my son and now he is giving it a workout on a regular basis. No complaints!

    >Rating: 2

    Sticky. Poor experience with Thomson

    I've used it several times

    Purchased new. Sticky from the get-go. 5-7 mm left in the 100 mm post at full extension. I contacted Thomson and was told I should send it in as it could be a pressure issue. They sent me a reconditioned replacement. That on arrived. Same issue. Contacted Thomson and same guy told me the amount of sticky, non-exteded travel I was experiencing was within tolerances. Whoa! I could have avoided the unistall and install of the post and replacement had they taken that weak position originally. I am bummed because the experience soured my feeling toward the brand, and I have had nothing but Thomson stems and posts for 20 plus years. :-( The company has a history of making aerospace components and prides itself on accuracy and precision. 5-7 percent travel tolerance is not accurate, nor precise.

    >Rating: 2

    Post gets stuck. Bad cust. support.

    I've put it through the wringer

    First let me clarify that I have many Thomson products and have always thought they are very high quality. I’ve never had to use their customer support and have been under the impression (from other reviews) that they were first-class. But I feel it’s important to write this review to keep customers informed and Thomson honest… I bought the dropper post about year ago, so this review is based on many rides. The dropper is released by depressing a lever that is mounted to handlebars. The lever is short so it doesn’t get in the way when riding, but the movement of the trigger is directly downward. This can be an awkward movement for your thumb when you are riding. It is not a push movement like we see on other shock systems. The cable extends straight out of the lever (towards the front of the bike), which causes the cable to interfere with the brakes (I run XT hydraulic). The result is that the lever must be rotated down, which makes the movement of the trigger even more downward. Awkward. And sorry if this description is confusing – doing my best. The dropper release is VERY STIFF. I have pulled the cable out of the trigger several times just trying to actuate the dropper. This is especially true if the post has not been used in over three days or the weather is under 40 degrees F. My dropper has gotten stuck several times. I didn’t want to strip the cable from the trigger on the trail, so I just rode with the saddle down for a while until it shook loose. Hitting the saddle (hard) while you shake the lever (quickly) seems to help. You might think that my post is defective, and here is where the customer service comes into consideration. I wrote Thomson with a few questions about the post to be sure it was the post and to see if I was doing anything wrong. The support was pretty terrible. I asked questions like “how hard should I have to push on the lever to actuate the dropper”. The response: “I would recommend getting a feel of how much pull is required to engage the post”. This went on for several emails, culminating in Thomson directing me to remove the post, grab the cable with my hand, and manually pull the cable to move the actuator. This essentially compares the strength of my entire arm to the strength of my left thumb – pretty bad test and not quantitative at all. My conclusion is that Thomson thinks my post is normal and operating as it is supposed to. Therefore, my recommendation is to not buy this post – the risk of stripping your lever and getting a saddle stuck in the down position is too great. One more comment if you really want this post: Thomson also wrote that “some hacks use other levers with our dropper post”. Maybe others are having this same problem and also gave up on customer support. Perhaps this is a way to make the Thomson dropper reliable.

    I have had nothing but awesome support from Thompson. Was an early adopter of this post and the dropper just got serviced (minor stiction) and it's now again perfect. After hundred miles more of singletrack and paved trails with a lot of stair jumps (im about 200 pounds) not one bit of play. The lever routing issue was easily resolved with a simple cantilever brake noodle. Looks clean and works perfectly. Best seatpost out there and I have had many.

    >Rating: 1

    Failed after a few month

    Stopped working after about a year

    >Rating: 5

    Long term use review

    I've put it through the wringer

    I've been running this post for almost 2 years now, and the only issue may already be resolved by the newer model remote lever. The original lever is not as ergonomic or smooth around the edges which is more of a comfort issue than function. Otherwise, I use this dropper dozens of times every ride regularly trimming the seat height to match the terrain or to reduce fatigue. It's action is smooth, well modulated and very controllable. The quality of the clamp is pure Thomson (top notch). It's currently in my 2011 Trek HiFi. The only maintenance I've done is replacing the cable once and just keeping it clean.

    >Rating: 5

    Excellent dropper

    I've used it several times

    Although I have only used it for a couple of weeks- I am loving it already. This is my first dropper so have nothing to compare it to but has met or exceeded my expectations. Also- it looks really sharpe on my bike (as a side note).

    >Rating: 4

    Old School meets New Cool

    I've used it once or twice and have initial impressions

    You know that Thomson makes awesome stuff. I replaced my set (lay) back seat post with this one. Thing is I was always sliding to the nose of my saddle when I was climbing steep stuff anyway. The bike did not come with a quick release so the seat was high all the time. I am a weight weenie, that is my bike, not actually me. Adding 500 grams took a lot of pondering. Is is really worth spending that much $ to add additional weight? Well...I did it. I have not had much time on the seat post, and the new position and another lever takes a bit getting used to. The setup was easy, however, I added a (brake cable) noodle to keep the cable bend smooth, tucked in and clean. I really like having the seat out of the way, especially being able to do that on the fly. I just require a bit more practice to make using the seatpost smooth and automatic. Choosing the Thomson seatpost was a no brainer for me. Thomson stuff is just that good.


    This is not the bike I expected from a weight weenie!


    All, Since the Thomson site is under construction I was hoping you could help me out. Based on good reviews the Thomson Elite 27.2 seems to be the best dropper on the market. However, I have a large frame (really need a medium) and I'm concerned that at full extension it will raise my seat height. I did have the bike sized a few months ago and I'm very happy with the current driving position. My questions are: 1. Can the post be inserted into the frame so the post collar sits on or is just above (a few mm's) the frame? 2. If not what in the Max insertion length? If you can give me the dimension from the bottom of the post that will be helpful. 3. If you can insert all the way and the dropper is extended out fully what is the dimension from the bottom of the collar to the top of the post (where the seat rail sit)? 4. Can you verify that the overall length is 430mm? 5. Do you think they will be releasing a covert version of the 27.2 in the future? Thanks, Alan

    >Rating: 4

    Great dropper

    I've put it through the wringer

    No issues with this thing. Made very well, and has a great lever as opposed to some of the plunger types on the market.

    >Rating: 3

    Installation issues!

    I've used it several times

    The cable included is too short. With the current routing it keeps getting caught in my pivots in the down position. Nothing like a seat that rises on its own.

    >Rating: 5

    Thomson Dropper Seatpost

    I recently purchased this dropper post, so I haven't had it for a long time yet, but it seems to be working amazing so far!

    >Rating: 5

    Worth it.

    I've put it through the wringer

    I've used this post for over a year and haven't had an issue with it. Smooth up and down and easy to use/mount lever. Thomson quality for sure.

    >Rating: 4

    Pretty good, slightly sticky.

    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.

    Same just happened on my new post, sticks at the last 1 cm of rise. Under 30 day exchange so going for a new one.

    Did the rebuild get it right? My post never extended to full height and the replacement also did not. Thomson said that is normal. Curious if that is the feedback you got as well.

    I too had a post with stiction. It is a common issue--the last 5 mm would remain in the post unless manually pulled. If you want a post to fully extend, you will be disappointed with this one.


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

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

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

    >Rating: 5

    Best I've used so far

    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!

    >Rating: 5

    Beautiful piece of equipment

    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. ***Update*** 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.

    >Rating: 2

    Play in the post after 1 month

    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.

    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.