Everything you need to know about Bike Seatposts

Widely lauded as the most important technological advancement to hit mountain biking circles since suspension technology, dropper seat posts are quickly becoming one of the most sought after features on a mountain bike.
Regardless of whether you’re looking to enter the world of dropper posts, or simply looking to upgrade, with the comprehensive information on all things dropper posts below, you’ll be dropping it like it’s hot in not time.
Put simply, a dropper is a height adjustable seat post that allows a rider to quickly and easily lower the seat height when riding along. A dropper seat post operates via the use of a handlebar, or seat post located remote lever.
There are a number of benefits to using a Satori dropper seat post, chief among is the ability to lower the seat post down, and out of the way to allow you to lower your centre of gravity to dip, carve, pop and shred to your heart's content when attacking technical sections of trail.
How a Dropper Post Works

Dropper seatposts work in a remarkably similar fashion to an office chair, in that you put your weight on the dropper post and push the lever, the seat goes down. Lift your weight off the post and push the lever, and the seat returns to its original position. Of course, the technical inner workings are more complicated than that, but that’s the general gist of it.
The innards of dropper posts are typically pneumatic, meaning that pressurised gas or air is responsible for holding the seatpost in either its fixed or infinitely variable position.
Traditionally the first dropper posts were adjusted with a lever at the post itself. Whilst this is still used sparingly, these days a dropper post is almost exclusively operated via a remote lever mounted to the handlebars and connected either atop the shaft of the post or at its base via a mechanical cable or hydraulic hose.

Why Dropper Posts are of Benefit

Dropper posts have opened up the possibilities of just how quickly riders and their mountain bike can adapt to varying terrain. With the flick of a switch, riders now have the option of comfortable and efficient pedalling, or confident descending with ample room for the bike to move beneath them without a saddle in the way.
They are also allowing frame manufacturers to create bikes with steeper seattube angles, perfect to help with getting your weight forward for easier climbing, but then the ability to get the seat out of the way once the trail turns around.

Selecting a Dropper Post

As dropper posts continue to be developed, more and more key players are entering the market. Whilst this is good from both a technological and durability point of view, the sheer wealth of options on the market can be overwhelming for a new buyer. Below, we sift through the key aspects of dropper seatposts and what to consider in your search.

Seatpost Length and Travel

The amount of travel a dropper post has refers to the amount of up and down movement on offer. Most posts will come in a choice of lengths, often linked to the amount of travel, or drop, on offer.

Typically, droppers are available in travel lengths of 80mm,100mm, 125mm, and 150mm, however, both longer and shorter options also exist.
Before buying, make sure the post is long enough when extended to give your preferred pedalling height. Measure the amount of exposed seatpost you have in a fully extended pedalling position. Just like a standard post, droppers will have a minimum insertion line.

As the length of travel increases, the overall length of the post will grow. More commonly than a dropper being too short, is it being too long. Be sure that with the post fully extended, that the height will not be too much. If it is, look for a post with a shorter travel and shorter design.

Also, consider how much of the post will fit inside of your frame without clearance issues. Many droppers posts cannot be trimmed, so you’ll need to find a length that provides perfect pedalling height, but without excessive spare length.
For this reason, it’s important to take your riding style, frame size and height into account when selecting a dropper post. As an example, small frames will rarely be able to accommodate a 150mm travel dropper, while taller riders may need to seek out a post with extended travel.

Fixed or Infinite Adjustment

There are two ways in which a dropper posts extend through their travel, preselected (aka, fixed travel), and infinitely adjustable.

The vast majority of posts are going to offer infinite adjustment. That means you can stop the post at any point along its travel. This is largely the prefered option purely as it allows a rider the ability to fine tune their saddle height depending on the situation.

Alternatively, some dropper seatposts will come with preset, or fixed positions. Depending on the seatpost itself, the number of fixed positions can vary from a basic up and down, to as many as 10 preselected heights. The main advantage of a fixed dropper seatpost is that they provide consistent and repeatable heights for riders to get accustomed to. Another benefit, as claimed by a few brands, is that the fixed designs are simpler and therefore more reliable. However, our experience is that both types are comparable in the durability stakes.

Mechanical vs Hydraulic

Most dropper seatposts use hydraulic or pneumatic pressure to be raised up and down, but the question of mechanical and hydraulic refers to how the remote lever is attached to control the unit.

A full hydraulic dropper post uses a sealed hydraulic remote to control the seatpost. The system itself works much in the same way as a hydraulic brake cable, whereby a piston (the lever) pushes fluid through a hose which actuates the dropper at the other end. The advantages of hydraulic cabling is that it is impervious to debris, there’s no cable to wear out and the hose can be routed through any angle without increased friction. However, such a system may require fresh hydraulic fluid on a seasonal basis. Currently, RockShox is the only company to offer a full hydraulic seatpost.

By comparison, just about every other dropper post on the market uses a mechanical lever, connected to a gear cable for control. Mechanical levers use a braided stainless steel cable that is threaded through gear housing and attached to the dropper post. The main advantage of a mechanical lever is that they are simpler and easier setup than their hydraulic siblings.

Handlebar Remote vs Seatpost Lever

A dropper seatpost is actuated via the use of either a handlebar located remote or a seatpost lever. The remote, or lever itself will be connected to the dropper post either via a mechanical cable, or via a hydraulic hose.
As previously mentioned, seatpost levers were traditionally the more popular when the technology was in its infancy, however, as dropper seatposts are becoming more refined, handlebar remotes are by far the more popular option. This is largely due to the fact it’s much easier to adjust on the fly without having to remove your hands from the handlebars.

Different brands each have their own dropper post lever designs. Older designs typically place the lever on top of the handlebar on the left side, allowing space for a left-hand (front) gear shifter. The rise of 1x gearing has seen space become available for a more ergonomic below handlebar position for the dropper remote.
In this way, the latest remote designs work much like a shift lever, operated by your left thumb. Where some posts don’t come with such a remote, aftermarket options are becoming readily available, with the likes of WolfTooth, OneUp, PRO, RockShox (to work with RockShox posts only) and others offering such an upgrade for relatively little cost.

Internal (Stealth) vs External Cable Routing

As with brake and gear cabling, dropper seatpost cabling can be routed both internally and externally of the frame.

Internal cable routing, commonly referred to as stealth cable routing, is the most common method of cable routing on modern mountain bikes. Following the same cable guides as gear and brake cables, internal cable routing means that a dropper post is connected to the remote lever at the shaft of the post. There are a number of benefits to internal cable routing including a sleeker aesthetic, reduced risk of contamination from dirt and debris and reduced chance of damage in the event of a crash.

External cable routing is common on more affordable dropper posts and for those fitting a dropper post to an older or entry-level mountain bike frame. The cables are typically routed outside of the top tube or downtube and attach to either the head or shaft of the post itself. The advantages of an externally routed dropper post is that they’re easy to fit and service. No having to fish around inside the frame looking for cable ends, just attach the cables to your frame, insert the post as per normal and away you go.

If looking for an external routed post, we strongly suggest picking one that sees the cable attach to the shaft, instead of the head. This is simply because the fixed nature of the shaft-mount means your cable length does not need to adjust to the seatpost height, therefore providing a far cleaner aesthetic and less chance of damage.

Seatpost Diameter

As is the case with standard, or fixed seatposts, dropper seatposts are available in a number of different seatpost diameters. The most common options are 30.9mm, 31.6mm and 34.9mm, however, skinnier 27.2mm posts are also available in select models.

The overall diameter will be dictated by the frame you plan to fit the dropper seatpost into. The easiest way to check this is to remove your existing post and read the size markings at the bottom of it. If your post is a weird size, then you may need to consider going a size smaller in the dropper post and finding a suitable shim to make it fit.

Larger diameter seatposts are regarded as adding stiffness and strength, as well as providing greater space for reinforced internal parts, all leading to improved durability. For this reason, many of the latest mountain bikes have increased seattube diameters.

Saddle Clamps

Just like choosing a rigid seatpost, saddle clamp design is worth considering in a dropper too. Most posts use the twin-bolt method, which allows wide compatibility with both metal and carbon railed saddles, and near infinite angle adjustment. Given the choice, this is our preference.

However, a number of posts make use a single-bolt side clamp, which does require addItional parts to swap between metal and carbon railed saddles.