Forgot to add that the existing deopper is a 31.6x360mm

 

OneUp has a "V2" dropper coming out...and with adjustable extension...it might work for your application. If you scroll to the bottom...there are various length measurements.

https://www.oneupcomponents.com/collections/dropper-posts/products/dropper-post-v2

 

Thanks for the info, looks like that dropper will have a 207mm base (i've since learned the proper term is "max insertion length").

I found an excellent spreadsheet of dropper posts measurements on the web, and it looks like KS has some very short "base" models in the 155mm range (but with 80-100mm travel only).

 

I looked, but couldn't really find anything with 150ish max insertion that had 125mm travel or more. Just seems that the post needs that much overlap (50-75mm between the upper and lower bushings) with the inner tube at full extension for structural reasons.

Examples:
9.8 Fall Line R with 125mm travel, and 190mm of post below the collar (internally routed)
Vecnum MoveLoc XC with 100mm travel and 175mm of post (cut) (ext routed)

Hopefully this explains why you might be asking for the unrealistic:

What you are trying to ask for, is a post where the inner tube doesn't extend this far into the outer tube. Engineering challenge that's beyond me...

 

I have a frame with 190mm of possible insertion before a bend in the seat tube, but I need enough exposed post at full extension that to accommodate the full dimensions, the best solution available to me to achieve the maximum drop was to use a 150mm Oneup post (V1), and shim the travel down to about 143mm. It's just plain impossible for me to get a dropper post with the collar slammed AND to be the correct length at full extension on the frame I have.

So, my seatpost collar is a decent bit above the seatpost clamp on the frame. It is what it is.


0404191452 by Nate, on Flickr

 

What about the BikeYoke Revive? I seem to recall that it has one of the shortest max insertion length.


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What about the BikeYoke Revive? I seem to recall that it has one of the shortest max insertion length.

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The Revive 160 falls right between the Oneup 150 and the 170. So it seems to fall in line with Oneup's (v1) dimensions pretty closely (max insert relative to drop).

I think what sets the Oneup apart is the ability to reduce the amount of drop so you can fine tune it to fit the bike. Of course, with the V1, you only have the 150 and 160 to choose from. But in looking at the numbers, it also appears that the Oneup V2 post is a hair longer than v1 (in the max insert dimension). At this point, I'm glad I snagged a v1 because the v2 would not give me as much drop in my situation.

So it looks like the Revive actually has a shorter max insert than the v2 Oneup post. Just no ability to customize/shorten the amount of drop.

 

-removed-

 

The new Reverb C1 has significantly shorter overall lengths, travel up to 200mm, a purge valve (similar to Bikeyoke Revive) as well as other improvements. Still a stupid a hydro remote though. Early Reverbs were pretty problematic. B1s have been pretty good. Mine has been trouble free for 2 years. Third (fourth?) time's a charm?

 

I've run into this problem now TWICE on small framed bikes for ladies I've dated over the last few years The issue also occurs on small mens bike frames, so it's not just overlooking women, it's just bad design/work/qa/whatever!

A Transition Patrol, and now a Haibike both have 140mm max insert depth. So a dropper with 220cm of insert depth has 80cm sticking out, plus the nut/seal at 33mm or so, and then 125 mm of drop on most "short" posts. So we're looking at 238mm ontop of the frame. I'm 5'10" and I can't even get on either of these frames at full extension and even dropped it's a bit much for the ladies it was intended for.

Not sure what the industry is up to, but they keep mucking up bikes in the smaller sizes!

 

So I found a solution!

The Brand-x Ascend 85mm dropper. 27.2mm diameter. Get that and an adapter sleeve for $10 from cane creek and you're in business!

The jist is that most droppers have 200-230mm of insert, and then 100-175mm of rise. If you're a shorter person... none of that is terribly useful to you, and the frames can't take nearly that length due to the suspension pivots and what not.

The haibike my Fiance got only had 150mm of insert! Well lucky us, the Brand X acend has pretty much that for insert. While 85mm of drop may not be all that awesome for the cool kids beating off over specs... it's just right for my 5'4" fiance to get all the drop she needs and get the ideal seat position on a frame with engineering limitations.

 

So I found a solution!

The Brand-x Ascend 85mm dropper. 27.2mm diameter. Get that and an adapter sleeve for $10 from cane creek and you're in business!

The jist is that most droppers have 200-230mm of insert, and then 100-175mm of rise. If you're a shorter person... none of that is terribly useful to you, and the frames can't take nearly that length due to the suspension pivots and what not.

The haibike my Fiance got only had 150mm of insert! Well lucky us, the Brand X acend has pretty much that for insert. While 85mm of drop may not be all that awesome for the cool kids beating off over specs... it's just right for my 5'4" fiance to get all the drop she needs and get the ideal seat position on a frame with engineering limitations.

Curious what the length on that post is. Our 120mm (shimmed to 100mm) has a length without actuator of 345mm (325mm). The CRC website shows 350mm for the 85mm post.

*edit - Found the length details below

85mm drop Brand X Ascend
Collar to rail - 155mm
Length w/o actuator - 316.5
Length w/ Actuator - 350mm

120mm (shimmed to 100mm) OneUp V2
Collar to rail - 153mm (133mm)
Length w/o actuator - 345mm (325mm)
Length w/ Actuator - 360mm (340mm)

Jon

 

I think approaching the math is incorrect. Here's the math I did, that worked for us and gave us results that matched our measured needs.

That's the oneup numbers. See measurement F.You take that and subtract the denoted 15mm for the actuator.

So on the 120/100mm OneUp dropper you mention, F is 207mm, minus 15mm. 192mm of insert length minus actuator. Pretty good compared to most of the competition, but only by 20mm or so over my recalled average of around 220mm on most. So less than an inch.

Here's the Brand-x specs. They have A+2 for "insert length", which You then subtract 35mm for the actuator.

The 85mm Brand-X is 195mm, less 35mm... so 160mm of insert length less actuator. That's 60mm less insert length than my recalled average of 220mm. That's over two inches shorter.

 

I think approaching the math is incorrect. Here's the math I did, that worked for us and gave us results that matched our measured needs.

I'm stoked you got a solution that worked for you.

I'm only chiming in because I think looking at the insertion in a vacuum is a common mistake. IMHO the dimensions that matter in 99% of cases are extended stack B from our chart (Collar to rail) and either Length A or E depending on whether your insertion is restricted by the actuator or the post.

For simplicity I'll only consider our 120mm post when shimmed to 100mm and assume that you are only restricted by the post (not the actuator).

Proper saddle height for pedaling is a constant. Your photos show the Brand-X post fully inserted. That means that your proper saddle height must be 155mm (the collar to rail distance of the Brand-X post). The collar to rail distance of the OneUp V2 100mm post is 133mm. That means that to achieve your proper saddle height the OneUp V2 would be 22mm higher than fully slammed. Yes our lower tube is longer (192mm) but only 170mm of it needs to be inserted into the frame to achieve the proper saddle height (versus 161.5mm of the Brand-X). Maybe that extra 8.5mm of required insertion is a deal breaker, I'm just trying to illustrate that the difference isn't the 32mm you outlined above.

In addition IF the actuator is an issue The OneUp V2 100mm post would be inserted 10mm less than the Brand-X 85mm post.

I hope this helps the community.

Jon @ OneUp.

 

 

This is precisely what the issue is for some short people. While the pedal height is constant, the fully slammed seat and still not being able to touch the ground is the concern.

So in your diagram, the F measurement is unable to be fully inserted into the frame. For example on my wife's Trance, there seems to be only 150mm of room for a post to be inserted before running into the suspension/bend in the frame. What is needed in her particular case is a dropper with ~150mm max insertion to set the seat lower when dropped, but still 100-120mm of travel for proper pedaling. I haven't found the solution for this exactly, but am open to suggestions...?

 

That's roughly where my fiance was at. 150mm of insert was the most we could get, she needed 120mm of rise or so from the top of the seat tube. With the collar adding 28mm, and the rise of the seat at 85mm, we're pretty much right in the vicinity for ourselves, and it sounds like just what you need.

 

I’m in the same boat looking for short seat post when collapse. Initially shredjesse post make sense but then I selves into it further and realized the important thing is not the insertion rather the total length while collapse. In this case the one up is actually shorter when collapse. Even though it has 120mm travel compared to brand x 85mm travel.

so here I am still looking for solution for short people. If anyone realize there is a market for it, my wife would be really happy.

 

I stumbled across this post after searching for a replacement dropper for my Specialized stumpy. I'm short with a small frame and am getting the same problem with my dropper bottoming out before it hits the collar. It seems as though I only have about 6 1/2 inches of max insertion length yet most droppers are around 8 in before any linkage.
Right now in my search, the best dropper I've found is the Brand-X Ascend II Dropper Seatpost which has a maximum insert of 128 mm...however this is an external dropper, so not much luck finding something internal yet.

 

Currently OneUp droppers are the ones with the lowest stack height, followed close by BikeYoke droppers. Regarding insertion length for the same travel length, if I recall correctly, they are both around the same. But they have different travel length, which will give you the option to get a post to best suit your needs.

 

The BikeYoke Divine looks promising with a 145mm insertion when cutting the bottom.

Where the OneUp Seems to be at 207mm (D)

Or for half the price, the KS Rage-I (D)

 

Did you go with the Brand X Ascend CX, and then shim from 27.2 to 31.6? We got a diamond back Clutch that my son is riding and are having the same issue.

 

found this list which lists a ton of post lengths Dropper Seatposts

 

Fast forward to 2022, we now have OneUp V2 90mm, with insertion length 167-15 mm= 152mm, which is about 6" of insertion, however, 90mm is a bit low of an extension. About 3.5", I can ride a bit better to 4", which is 100mm. However, there does not seem to have a dropper post with this specs; a 152~mm insertion, with a 100mm dropper height. I guess 90mm will do but OneUp V2 is so out of stock now for a few months. Anyone knows other brands that are closed to this 100mm? I've researched KS-LEV, 155 mm insertion, but 80mm dropper height, a bit low. KS Rage-i has rather good insertion length, 161mm but 75mm, I think both are about the same, Rage-i will always sticks out a bit plus the collar and then extend < 3". Where the LEV insertion is 3mm sticking out, but only 80mm ~ 3". So OneUp V2 90mm + collar might be just right.