Dropper post with a curved seat tube

conman1395 · Mar 23, 2018

Hi everyone,

I just bought a 2017 Trek Stache 5 and love it. Now I want to add a dropper post. When I test rode the bike at the shop they had to cut off a little of the seat post because it was too long bottomed out. Now, it is just about right (maybe a half inch too tall still).

The issue: The overall length of the post from underneath the rails to the bottom of the post is 13.5 inches (342 mm) and I have the post all the way down so the 342mm is the maximum overall length of a dropper post I can fit. I'm having trouble finding a dropper post with that or less overall length. Unfortunately the Stache has a curved seat tube so I can't get it any lower. Do you guys have any dropper post recommendations or am I going about this the wrong way?

Thanks,
Connor

Aglo · Mar 24, 2018

With that size limitation it's hard to find a dropper. I mean, you have options but the travel will be limited, like the 9point8 Fall Line with a factory overall length of 325mm and 75mm of travel, and possibly you may be able to further customize the travel and increase the travel by 15mm or less (90mm total), increasing the overall length to 340mm or less, but it's only a supposition. Possibly, if you or your LBS are mechanically inclined you may be able to do the same with other droppers, but the Fall Line is able to do what you need from factory.
Other option is the Vecnum moveLOC 2, with an overall length of 423mm and 100mm of travel, possibly more travel depending on you maximum insertion value.

Fall Line

Pros:
Infinity adjustment.
Internal routing (it can be a Cons)
Cons:
Heavy(ier)
The most expensive
Only 75mm of travel

moveLOC 2

Pros:
Lighter
At least 100mm of travel (I'm not sure because your data is incomplete/limited)
Cheaper than the Fall Line
Cons:
Indexed positions
External routing (it can be a Pros)

Please note that this are only extrapolations because you only give the max overall length as data.
You also have some droppers from KS, but they have even more limited travel, so I didn't included them, give them a look if you don't like my suggestions.

P.S.: please also note that it is 3 in the morning, English isn't my first language, and I have single malt Irish whiskey running in my veins.

Black Squirrel · Mar 24, 2018

The fox post is close, a 30.9 post with a shim will go in a touch more.

A thinner seat or shorter cranks will help also.

You also set up a dropper a little higher than a rigid post, at least I do. I shoot for max pedaling efficiency with the dropper up, which is usually about an half inch higher than I would set up a rigid post.

One Pivot · Mar 24, 2018

I bet your seat isn't as high as it should be.

Droppers and bent seat posts go hand in hand. How tall are you, and what size frame? I bet any off the shelf 125mm post will do it.

conman1395 · Mar 24, 2018

Thanks for everyone's replies. In an attempt to answer everyone's posts:

I'm 5'10" with a 30" inseam. The exposed part of the seat is almost 150mm converted from inches, but I don't remember what the inches were. I just remember initially looking at 150mm droppers after my measurements

I'm almost certain the seat is high enough because before they cut off the post my hips were rocking while pedaling backwards, quite a bit it seemed.

I measured right below where the mount for the seat rails would go so if I was supposed to measure directly where the rails go I suppose that adds 10mm or so.

The one that seems like it'll work the best is the CrankBros Highline at 100mm. I'd much rather have something closer to 150 but I understand that's probably impossible given the length I'm working with. I suppose I may be able to get an inch or so if I took out the top bolt out of bottle mount eyelets on the seat tube but I don't want to cause damage to anything by doing so. Let me know if there's anything else I should provide.

Thanks again

conman1395 · Mar 24, 2018

I'll also add I wouldn't doubt if there's something I'm doing wrong. I searched the forums and Google for a while looking to see what others have said and I didn't even find someone with my issue. Where should I be measuring my seatpost "overall" length from to determine what dropper post I can fit?

Black Squirrel · Mar 27, 2018

With some digging most manufacturers have prints of the posts that show all dimensions.

Matt_Edger · Apr 11, 2018

Call Trek Customer Service. They sent me all the exploded diagrams that I needed while trying to upgrade my bike. It’s was a 5 minute call and they e-mailed me almost instantly adterwards

Sent from my iPhone using Tapatalk

foresterLV · Apr 11, 2018

BikeYoke Revive 125 have 365mm length from rails to bottom tube plus few cm for narrow cable attachment thingy (which should be able to fit into curved tube for some degree).
find drawings here (in drawings and dimensions) - https://www.bikeyoke.de/en/seatpost-revive-125-30-9.html
very good dropper in my experience (there is a big thread on mtbr here too) and also very compact one (on my fat bike I was able to replace 125mm Reverb with 160mm Revive, and it drops lower then Reverb - almost to the collar).

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conman1395 · Apr 11, 2018

Hey everyone,

Thank you so much for your suggestions! I ended up buying a 100mm CrankBros Highline. I got it brand new for $150 off MSRP and it was one of the shorter overall length ones (345mm). Somehow, though, it is about 1.0 - 1.5 inches too long even though the overall length advertised is shorter than what I measured on my seat post. I think it has to do with the mechanism CrankBros uses rather than the other cable actuated brands. It's a large cylindrical mech vs just a linear pull. It does however feel about right if I remove the top screw for the seat tube bottle mount. Any opinions on that and whether or not it's a bad idea? I was thinking of cutting the bolt shorter so it wouldn't get in the way.

ForesterLV: That BikeYoke looks sick and would have been a great choice.

Aglo · Apr 11, 2018

The Revive does looks sick. I have over 2000Km on mine since May last year and it still works as the first day I installed it. A great dropper seatpost if not the greatest dropper seatpost.
Regarding your problem, I would cut the bolt shorter and would apply a good amount of Loctite.

Dropper post with a curved seat tube

conman1395

Aglo

Black Squirrel

One Pivot

conman1395

conman1395

Black Squirrel

Matt_Edger

foresterLV

conman1395

Aglo

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