The seatpost is the tube that the seat of the bike rests on. She merges the saddle with the frame in single system and allows these two parts to interact.

Why do you need a seatpost?

The main function of the seatpost is to adjust the height of the saddle. Also, with the help of special locks, the pipe adjusts the angle of the seat. The correctness and convenience of landing a person on a bike, obtaining the maximum efficiency from the efforts of a cyclist depends on these parameters.

What material should the seat tube be made of?
Now about 90% of bicycle seatposts are made of aluminum. This metal is very light, but has strength, which is enough to withstand significant loads. Seat tubes for bicycles of very cheap series, for example, "Ukraine", are made of steel. These pins are very rigid and strong, but much heavier than aluminum ones.

For bicycles used in sports competitions, carbon seat tubes are installed. Such parts are lighter than aluminum, and can reduce the weight of the bike by 100-200 grams. At the same time, carbon pipes are not inferior to aluminum in terms of strength. That is why athletes love them.

Scandium seatposts are installed on the most expensive and prestigious bike models. They are even lighter than carbon fiber, but have a very high cost.

What should be the length of the seatpost?

The length of the seatpost should be at least 30 cm. Most modern bicycles use pipes 30-40 cm long. On some models of economy class bikes, very short seatposts (up to 15 cm) are used. This feature does not allow you to push the pipe higher and observe proper fit on a bike.

Checking the length of the seatpost when buying a bike is very easy. You just need to open the eccentric (lamb), which is located at the base of the pipe, and slightly pull the tube up. If this part is short, it will easily slip out; if it is long, it will drag slowly and require effort.

Determining the right seatpost length for a particular bike is easy. To do this, it must be extended to the maximum possible mark, which is indicated by a long white dash. After this procedure, you must sit on the bike. If the legs do not touch the asphalt during the draft, but reach the pedals at the lowest point of their rotation, then the seat tube is long enough. If the lower limbs reach the asphalt, you need to change the device or bike.
In good bike shops, the bikes that are in the window have the saddle raised to the maximum and no additional manipulations are necessary with them. It is enough just to saddle an iron horse.

What should be the diameter of the seat tube?

There are 3 main seat tube diameters for bicycles:

• 25 mm
• 27.2 mm
• 31.6 mm.

The 25 mm diameter was used in Soviet bicycles. Now bikes with this pin width are not produced, but frames with it are actively used. Diameters 27.2 and 31.6 mm apply to all modern bicycles, regardless of class and purpose.

Some manufacturers make frames with different seatpost hole widths. Pipes for them must be selected individually. You can find out the diameter of the seatpost in the characteristics plate, which is attached to the bike in the window or posted on the store's website.

What types of locks are fitted to seatposts?

There are 3 types of locks that are placed on the seatposts:

1. Single bolt. Such devices roughly adjust the inclination of the saddle.
2. Double bolt. These mechanisms allow you to fine-tune the position of the seat.
3. Original. Some manufacturers install very complex locks of patented designs on their premium bikes. The high cost of pins with them is not always justified when using a bicycle.

Depending on the position in relation to the seatpost tube, the locks are of the following types:

• With a shift back - the most common type.
• No offset. Devices of this type provide a slightly forward fit.

What additional devices are equipped with seat tubes?

shock absorber

Until the early 21st century, a seatpost was simply a hollow tube with a saddle mount at one end. But since the early 2000s, shock absorber pins have become popular. Such devices significantly soften the load and impact of the saddle on the gluteal muscles when riding on rough terrain or on dirt roads.

All cushioning mechanisms for seatposts are divided into 2 types:

• telescopic,
• lever.

Pipes equipped with the first type devices are relatively cheap, but have a short life, especially if the bike is used by a person weighing more than 90 kg.

Pins equipped with mechanisms of the second type cost several times more, but provide the maximum reduction in the load on gluteal muscles.

telescopic device

Also, bicycles that are designed for off-road riding (dual suspension) are sometimes equipped with telescopic seatposts. They consist of two pipes. The top of them is drawn into the bottom. This feature allows you to push the saddle up as much as possible when riding on the highway and reduce its height when walking off-road.

height adjuster

A subspecies of telescopic seatposts are tubes with a height adjuster. In them, the cable from the guide device is pulled to a special button mounted on the steering wheel. With the help of the latter, the cyclist can, without getting up from the bike, change the height of the saddle. Regulator tubes are rarely factory fitted to bicycles. You can buy them only in stores for professional riders.

The final choice of seatpost depends only on the preferences and financial capabilities of the bike owner. For walking around the city, a simple pipe with a single-bolt lock shifted back will suffice. Only for extreme off-road racing do you need complex seat tubes equipped with various “gadgets”.

With a shock absorber is a special device designed to connect the saddle and frame. The shock absorber softens the bike ride on uneven, bumpy roads. Distinctive feature such a pin - a lot of weight.

What's this?

A seatpost with shock absorber for a bicycle adds weight to the design, so you have to choose between weight and ride comfort. The pin has special rails for fastening. They need to be put on the pin head and screwed with a bolt. This design is and is made in the form of a pipe connecting the frame and the saddle. It is attached with a clamp and fixed with a bolt lock.

The most common shock-absorbing pin designs are telescopic and lever. In them, the elastomer acts as an elastic element. The telescopic type is used in inexpensive seatposts. When the lever design comes into action, the saddle moves back. It is rarely used due to the high price. Seat tubes are made of steel, carbon fiber, aluminum alloys. The most common pin diameters are 27.2 and 31.6 mm.

Design

The seatpost with shock absorber is installed in the frame tube and secured with a clamp. In the upper part it has a lock in which the saddle guides are fixed. When the clamp is open, the seatpost moves up and down in the frame tube to adjust the seat height. Structurally, they are divided into depreciation and rigid. The classic rigid pin has a thin-walled tube with a lock on the end. This design weighs little, is inexpensive, durable, reliable, but not very comfortable.

The damping pin is equipped with a special mechanism that softens and minimizes shock during the trip. Such pins are most often made of aluminum alloys. Design features include:

• Diameter (standard from 27.2 to 31.6 mm).
• Length (for road bikes it is 270-300 mm, mountain bikes 350-400 mm). The smaller the frame, the longer the pin you need to buy.
• Lock (fixes saddle rails, adjusts inclination, longitudinal displacement). Locks are single-bolt, two-bolt, original, with a shift back, without a shift.

For example, the seatpost with a shock absorber is 31.6 mm in diameter, has a single-bolt mount, and is 35 cm long. The design is mobile and durable. Models of pins with parameters of 31.6x350 mm are manufactured by the Cycledesign brand.

How to install?

The seatpost with shock absorber must be inserted into the frame tube and secured with a bolt or eccentric clamp. Seat guides are secured with a lock. Single bolts have coarse seat tilt adjustment, double bolts have fine tilt adjustment. When adjusting the height, it is important not to install it in the seat tube above the mark marked on the pin.

Inside the pipe, it should remain ten to fifteen centimeters. If the pin does not move down, stop at this point. However, before installing it, make sure that the diameter fits the frame. To do this, you need to measure it with a ruler, caliper. Take advantage of the most in a simple way mounting: if the pin has a constriction at the top, it is inserted into the saddle mount and bolted.

Selection rules

Seatpost with shock absorber improves specifications designs. When choosing, it is important to consider the following points:

• financial capabilities (a hydraulic pin with a shock absorber is much more expensive than usual);
• comfort level (if you want to enjoy riding a bike, improve its functionality, appearance, and also get a saddle and adjustable height - stop for a model with a shock).

A pin equipped with a shock absorber is not only a comfort, but also a necessity Maintenance. If you want it to last a long time, follow the rules of operation. It is not recommended to lift it high, because due to high load pin may break. The disadvantages of parts with a shock absorber include the need to take into account the drawdown of the pin when adjusting the saddle when a cyclist sits on the bike. Over time, it increases.

Depreciation works in the direction of the axis of the pin. This means that it is not able to completely get rid of the feeling of discomfort while driving on bumpy roads. If the damping mechanism is stiff, it will not absorb small shocks well. Pins that are adjustable in height sometimes sag under regular load, have less strength, low-quality models even play and make rattling sounds.

Price

The seatpost with Suntour shock absorber belongs to the category of expensive bike components. Model SP12-NCX (27.2x400) costs 4500 rubles. This shock absorber pin, parallelogram with stiffness adjustment, weighs 765 grams. Pins without a shock absorber are cheaper. Such designs can be purchased for 500 rubles. Inexpensive shock-absorbing structures include VLX-SP09 with parameters of 25.4x350 mm.

The most frequently asked question from beginners: bike sizing. Often people who ride only a few times all summer give a completely wrong answer. As a result, beginners will get a bike that has a frame that is not suitable for their height, which will cause problems with their knees and affect their backs. The wrong frame size always leads to discomfort when riding.

This feeling arises with an increase in the distance traveled per day up to 30-50 km. Therefore, novice cyclists should listen to a few tips:

Please note that the frame size (ST) is indicated by the length of the seat tube.
Dimensional parameters of road, hybrid, city bikes are presented in centimeters, mountain bikes - in inches. Since road bikes became popular primarily in southern Europe, and mountain bikes were invented in the USA.
If someone says that a frame is suitable for you, for example, at 18", this is not a complete answer. Gone are the days when the length of the pipe at 18" spoke of a frame suitable for a person with a height of 1.75 meters. Now they produce frames with a variety of geometries, for various driving directions.

Now about the parameters. Below are drawings of mountain and road frames. Look at the following measurements: ST is the length of the seat tube, ETT (T/Th,L) is an imaginary line drawn from the center of the head tube to the intersection with the imaginary axis (passes through the seat tube). In general, ETT corresponds to the length of the bike, the main parameter when choosing a bike. Beginners usually do not look at him.
It is worth noting that both frames are intended for the same person. Although the parameter ST (frame size) is different. Therefore, a beginner advised to use an 18" frame may be wrong.
The example clearly showed the existing differences in the geometry of the mountain and highway frames. However, it is a mistake to think that frames belonging to the same class are the same. For example, a 21" MTB bike might be shorter, while a 19" bike might be longer.
When choosing a bike for height, you should first of all look at its length, since the inscription on the frame indicates the size of the seat tube, which is a secondary parameter.
The designation of bicycle sizes (18", 20", L, etc.) is misleading, because the frames have different geometries.

Mountain bike

Road bike
Beginners can dismiss such subtleties, but it’s better to take a closer look at choosing a bike size. (Better sooner than late!) If you like this hobby, the wrong frame length will force you to buy a new bike.
Modern bicycles do not have handlebar height adjustment without additional action. (exception - city bikes). You can't "replay the geometry" if the size is wrong.

Read on for tips to help you choose. mountain bike or hybrid:
1. Without fail, try the bike yourself. If there is no opportunity to ride, then sit at least;
2. When standing with both feet on the ground (bike between them), there should be a distance of at least 10 cm from the crotch to the top tube. An underestimated distance threatens injury in case of falls, during an emergency stop;
3. The longest bike creates a more athletic fit. To obtain high speeds, effective slope climbing, you need to “spread out” above the frame. If you need a bike for sports purposes, take it with long and low frames. Marathon runners use such bikes for long distances, although ordinary people soon begin to fall off their hands due to the serious load on them;
4. When slow, comfortable riding is required, short frames will do. For example, a city bike: the landing is almost vertical, you sit like on a stool, only holding the steering wheel. Long distance it is not so convenient to pass: the weight of the body rests on the spine. For serious riders, long frames are preferred;
5. The medium length frame is ideal for the advanced cyclist with no sport inclination. He will not need to “flatten out”, transfer weight to his hands, he will not have to sit on his coccyx. Having such a bike, you can drive tens of kilometers, while there will be no discomfort from landing.
Let's say that when you buy a bike, you decide that it doesn't fit perfectly. There is a possibility that you incorrectly adjusted it to your own height. How to customize the bike for yourself - below!

Steering wheel and stem
Modern bicycles do not have handlebar height adjustment. The steering stem (this is a short stick intended for fixing the steering wheel) has a length and an angle. There are outlets of various sizes. By purchasing the right one, you will improve the feeling of riding. Also, the spacer rings on the fork stem will help raise the stem relative to the frame. (If the length of the fork stem is enough for this)
It is possible to install the stem with an ascent, as well as with a descent. There are adjustable stems, handlebars with or without lifting. This will help change the height of the steering wheel.

Horns
Important element at considerable distances, allows you to change the position of the hands, body. They are placed almost parallel to the ground, with a very small rise. It should be possible to lay down on them with palms with the removal of the center of gravity forward.
This posture will add aerodynamics, cyclists often use this technique when moving into the wind. A good addition is having flat grips, you can put your palms on them.

Horizontal seat adjustment required
The saddle should be parallel to the ground. Some, for convenience, tilt the saddle forward or backward. This is fine tuning! In case of excessive tilt, pressure on the hands may increase (leakage, numbness, cramps), and pressure on the perineum - discomfort is provided.
A perfect fit is required. Lower the seatpost slightly (by a centimeter), this may allow for even alignment of the saddle.
In case the frame is not quite the right size, the position can be corrected by a longer handlebar stem, which has an offset seatpost, horns.

You will need to adjust the saddle height.


Many novice cyclists set the saddle at a low level. The result is the so-called "knees above the ears" landing. Which looks funny, and creates a danger to the knee joints.
The saddle height is required so that the foot standing at the lowest point of the pedal (with the toe placed) is slightly bent or fully extended when the pedal is hooked from below.
Place your foot on the pedal with your heel, it should be fully extended. The most important moment! It may seem uncomfortable that if you need to stop suddenly, it is impossible to touch the ground with your feet, unless you get off the seat. However, the well-being of the knee joints is more important than comfort.

Longitudinal seat adjustment
Ideally: the foot rests on the pedal in such a position that the pedal axis is located under the knee joint. This is achieved by advancing the saddle in the longitudinal direction.

Offset seat post
The part will be useful when, having performed the maximum longitudinal adjustment of the saddle back, there is a feeling that the fit is a bit short. The pin can provide an additional three to five centimeters.

These simple tips will help you find the right bike size for you. Remember that the size and adjustment of the fit on the bike are very important things, not only the mood of the rider, but also his health depends on them!