In the world of cycling, there are many disciplines that aren’t limited to specialized actions. Unlike BMX and trials, where riders perform exclusively tricks on highly maneuverable bicycles, disciplines such as cross-country, trail, and enduro require a more versatile approach to bicycle design.
In these disciplines, not only the lightness or off-road capability of the bike is valued, but also its versatility. This applies to the gear ratios of the drivetrain, the head tube angle, and the saddle position. One of the elements that significantly increases the versatility of a bicycle is a pneumatic seatpost. Let’s explore what this device is and what advantages it offers compared to a regular seatpost.
What is a Seatpost
A seatpost, formerly known as a seat pin, is used to attach the saddle and adjust its height and position relative to the bicycle frame. Modern seatposts are made not only from steel but also from aluminum alloys and composite materials such as carbon. Carbon seatposts are lighter than aluminum ones and have a longer lifespan, but they are more expensive. Some manufacturers experiment with titanium and alloys with magnesium additives.
Modern production technologies allow the creation of seatposts with variable wall thickness (butted), which increases their strength while reducing weight. Quality seatposts are made from rolled tubes, which are then subjected to machining and careful grinding to eliminate stress concentrators. Clamp parts are milled from forged aluminum, and fasteners are made from high-strength steel or titanium.
For extreme disciplines, curved seatposts are produced, providing optimal weight distribution for the cyclist. If your bicycle is not equipped with rear suspension, maximum comfort can only be provided by a seatpost with a shock absorber.
What is a Pneumatic Seatpost
A pneumatic seatpost, also known as a dropper post, is a device that allows instant adjustment of saddle height at the cyclist’s will. In the cycling community, it’s often called a dropper or pneumatic seat post. This is one of the most significant engineering achievements in the bicycle industry in recent years.
Areas of Application
A pneumatic seatpost is especially useful in disciplines where bicycle versatility is important. For example, in cross-country, where trails run through varied terrain with various obstacles, the ability to quickly change the saddle position allows for more efficient obstacle negotiation and time-saving.
The same applies to trail and enduro, where routes can include both descents and climbs. For comfortable climbing and reduced knee strain, a raised saddle is necessary, which shifts the center of gravity towards the handlebars and increases pedaling efficiency. During descent, the saddle is lowered, increasing rider maneuverability and allowing the center of gravity to shift backward.
Advantages and Disadvantages
The main and undeniable advantage of a pneumatic seatpost is the ability to instantly change saddle height on the go. There are few disadvantages, but they are significant: high cost (5-10 times higher than a regular aluminum seatpost) and greater weight (2-5 times heavier than a standard construction).
General Construction
A pneumatic seatpost consists of several main components: a pneumatic cartridge (usually serviceable), a cable with housing or hydraulic line to control the cartridge valve, and a handlebar lever (in some models, the lever may be located under the saddle).
Types
Currently, various types of pneumatic seatposts are available on the market, meeting different customer requirements.
By Mechanism Activation Type
There are four main types of control mechanisms for pneumatic seatposts:
- Under-saddle lever: the most budget-friendly but least convenient option, gradually being phased out of the market.
- Handlebar lever with hydraulic line: resembles a gear shift trigger but uses a hydraulic system. Requires periodic maintenance of the hydraulic line.
- Handlebar lever with cable: the most popular option, combining ease of control with simplicity of design.
- Wireless control: the latest development, providing maximum convenience but currently the most expensive.
By Cable Routing Type
There are three options for routing cables from the control lever to the pneumatic cartridge:
- External: cables run along the outside of the frame. Not the most aesthetic but a common option.
- Internal: cables run inside the frame, improving appearance and ease of use.
- No cables: available only for models with wireless control.
By Overall Construction Length
The length of the seatpost body affects the maximum travel length of the extendable shaft. Models on the market have body lengths from 295 mm to 560 mm, and shaft travel lengths from 35 mm to 210 mm.
By Seat Tube Diameter
There are four standard seat tube diameters: 27.2 mm, 30.9 mm, 31.6 mm, and 34.9 mm. The most common diameters are 30.9 mm and 31.6 mm.
A More Reliable Solution
The future of dropper posts is associated with solving a number of problems, such as bushing wear and the need for maintenance. There’s a trend towards returning to simpler coil-spring designs, especially for models with shorter travel. DT Swiss demonstrated the potential of such a design with their D232 model featuring 60 mm of travel.
For cyclists who prefer pneumatic dropper posts, some manufacturers have begun designing frames for specific seatpost models, allowing optimization of their characteristics and integration with the bicycle.
