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From what I've seen, the last couple of years saw a new product type come into light, and since its inception it has started to appear on bikes (such as this one, this one, or this one) as a stock item.

I'm talking about the "drop seatpost".

For the un-initiated, these are seatposts that are adjustable "on-the-fly", either by remote or a lever under the sadle. The idea is to allow the rider to find an optimal seat height to suit the conditions. This seems like a great idea, but what suffers as a result? I believe there is an inevitable weight penalty that would burden the gram-conscious amongst us, but what else might sway a decision for or against the purchase of one of these items?

I assume the potential problems will include weight, mechanical failure and cost, but what else might there be to the equation?

From what I have gathered these nifty looking contraptions come in a plethora of variations, and notable brands have created their own versions. I've seen them made by Fox, Rockshox, Crank Brothers, Specialized, KS and Gravity Dropper. Perhaps there are others as well.

So in addition, what differentiates each of these models and brands? What are the pros and cons of each? Is there one that stands out as a clear winner in the field?

Any help or insight is warmly welcomed, so thank you in advance!

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The price and the immaturity of the technology are obvious drawbacks. I am also very curious about thus feature, but intend on waiting for the prices to drop to the low 3-digit range. –  Vorac Oct 28 '13 at 10:29
    
Those have been around for 30 years, at least. –  Daniel R Hicks Oct 28 '13 at 12:19
    
@DanielRHicks, I had no idea they have been around so long! Why are they only becoming mainstream now if they have had so long to seep into the market? –  Saxman Oct 28 '13 at 22:58
    
Well, way back they were marketed to serious racers, those who would drop the post for a downhill, then raise it for the rest of the ride. But there were few racers that serious, and I'm not sure how advantageous it was for those who tried it. I'm a bit surprised to hear that it is now the "in" thing. –  Daniel R Hicks Oct 28 '13 at 23:25
    
IIRC, the old posts used a large hairpin spring (maybe 8" long) attached to the seat tube and to the post just below the seat, with the bend pointing toward the rear of the bike. A quick-release seat adjuster clamp would hold the seat in the desired position. –  Daniel R Hicks Oct 28 '13 at 23:30

2 Answers 2

There are generally two types of dropper seatposts, mechanical (e.g. GravityDropper) and hydraulic (e.g. RockShox Reverb). Mechanical dropper seatposts use a spring to move the seatpost and a bolt to keep it in place. This is a very simple design and there are few things that can break or jam, and the weight is also kept very reasonable since there are few parts needed to make it work. The drawbacks are that you only have a fixed number of height settings, i.e. fully extended, halfway extended, and fully lowered. This is because the seatpost is being held in place by a pin that goes through a hole in the seatpost.

A hydraulic seatpost on the other hand uses hydraulics to move the seatpost and thus allows you to place the seatpost at any height you like. The drawbacks are that they are more complicated, usually weigh more, costs a lot more and requires more maintenance. The advantages are the ability to lock the post at any height you like.

Mechanical dropper posts:

 + Mechanically simple and easy to maintain
 + Low weight
 + Cheap
 - Only a fixed number of positions for height adjustment

Hydraulic dropper posts:

+ Freely adjustable to any height
- Complicated
- Requires more maintenance
- Expensive

Static QR seat posts:

+ Requires no maintenance
+ Cheap
+ Low weight
+ Can be adjusted to any height
- Rider must dismount to lower and raise seat
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I have seen hydraulic seatposts and know how they work - my office chair has one! How do mechanical ones work? Can they be adjusted without getting off the bike? –  Vorac Oct 28 '13 at 12:56
    
Reach down and pull the knob located on the front of the post and sit down. Your seat will lock in the lower position. To raise, while sitting, pull the knob and sit up. aha, so they work fine. I have been living in the dark ages. –  Vorac Oct 28 '13 at 12:59
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Most high-end dropper posts have remote levers that mount on the handlebar to control the post, whereas most of the lower-end ones have a post mounted control. –  Aaron Oct 28 '13 at 13:36
    
@Vorac You can get mechanical and hydraulic dropper posts with or without a remote. I think the cheapest dropper post with a remote that you can get is this one: ebay.com/itm/… –  user1049697 Oct 28 '13 at 13:40
    
What I'm really interested in is more of a general breakdown of the pros and cons of Drop Seatposts, not just a comparison between the main styles. –  Saxman Oct 28 '13 at 23:03

The only disadvantage I can think of (that you haven't already listed) is the remote control: It's yet another control sat on the handlebars. This is fine if you're running a single chain ring (1×10 or similar), because it can sit where the front shifter would normally go. Less than ideal if you're running 2 or 3×10, have remote lockouts, a bell and so on.

Advantages: You can adjust your seat height according to the terrain you're riding. Riding down something steep and scary? Doing some jumps? Push the button, drop the saddle. Hauling up a big climb? Spinning along the road between trails? Push the button, raise the saddle. Until I had one, I couldn't appreciate just what a big difference it can make. I occasionally drop the post just for a couple of corners, or raise it just for a quick sprint before dropping again for the rest of the descent.

There isn't really a clear winner, yet. The Gravity Dropper design has been around for years; it's simple, proven and dependable. Of the current crop, the consensus seems to be that the Rockshox Reverb is "the one" (and comes specced on a lot of new bikes), although the more recent KS Lev and Thomson Elite Dropper are getting good reviews too.

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