Rear hub model
Model of the hub used in the rear wheel of a bicycle. See Front Hub Model for details.
Speeds
The number of speeds (gears) provided for in the design of the bicycle. Each transfer has its own so-called gear ratio — in this case it can be described as the number of revolutions that the driven gear (rear, on the wheel) makes in one revolution of the leading gear (associated with the pedals).
Different gear ratios will be optimal for different conditions: for example, high gears provide good speed, but are poorly suited for overcoming obstacles, because. the effort on the pedals increases significantly and the frequency of their rotation decreases. It has been scientifically proven that a cyclist develops maximum power at a cadence of about 80-100 rpm. Thus, the presence in the bike of several speeds allows you to optimally adjust it to different driving modes and features of the tracks in order to provide optimal pedaling force and frequency of their rotation. For example, on smooth asphalt it is best to drive in a high gear, and when overcoming a rise or entering a dirt road, you can lower it in order to effectively overcome resistance.
The number of gears in classic systems is directly related to the number of stars of the system (on the bottom bracket with pedals) and the cassette (on the rear wheel); it can be obtained by multiplying two numbers — for example, 3 stars of the system and 6 on the cassette give 18 gears. However, there is also the so-called planetary hubs — there are stars one at a time, and gear shifting is carried out by a mec...hanism built into the rear hub.
Note that the optimal number of gears depends on the purpose of the bike (see above), and it is not always necessary to have several of them. So, in mountain models, depending on specialization, there can be from 8 to 30 gears, in road ones — within 20-30, and some inexpensive city bikes and most BMXs do not have a gear shift system at all.
Planetary hub
The presence of a planetary hub in the design of a bicycle, more precisely, the rear wheel of a bicycle.
Such a bushing is installed directly on the wheel axle; the name "planetary" describes the type of mechanism located inside. The purpose of such a sleeve is the same as that of the cassette (see below) with several sprockets: it provides gear shifting. At the same time, the cassette itself most often has one asterisk and does not participate in gear shifting (although there are exceptions where the “planetary” is supplemented by a cassette with several asterisks).
The planetary hub has both advantages and disadvantages compared to the classic multi-star cassette. One of the key advantages is the closeness of the mechanism: it is not affected by moisture and pollution, requires virtually no maintenance and, subject to the rules of use, can last a very long time. If gear shifting is carried out only due to the “planetary”, the bike does not need additional rollers for the chain and it wears out less. Also, the chain in such models is constantly in one position, which allows you to install full protection on it (and it protects not only the chain, but also the cyclist's clothes). In addition, the advantages of planetary bushings include ease of adjustment, resistance to falls on the side, ease of adjustment, ease of switching (one switch is enough) and the absence of close and “opposite” gears.
On the other
...hand, such systems are much more expensive and heavier than classical switches of similar quality; they are more difficult to repair, make it difficult to replace the wheel and adjust the gear ratios if the initial value of the latter for some reason does not suit the cyclist. Yes, and the gear ratio (the difference in speed between the lowest and highest gears) of the planetaries is noticeably lower; the exception is perhaps expensive professional bushings, and even then not all. This makes climbing steep hills difficult (the gear may not be low enough) and fast driving, where high gears are needed, including when descending. Accordingly, planetary hubs are poorly suited for hilly or rough terrain. However, the gear ratio can be increased by adding a classic derailleur (with a multi-star cassette) to the bike — however, with this addition, many of the original advantages of the "planetary" are lost, such as insensitivity to pollution and a constant position of the chain.Freewheel cogs
The number of stars (gears) of different sizes in a bicycle cassette. A cassette is a part of the rear hub that interacts directly with the chain, in other words, a gear or a set of gears mounted on the hub. In classical gear shifting systems, the number of gears directly depends on the number of stars in the cassette (for more details, see "Speeds"); a single chainring is used either in single speed bikes or in planetary hubs (see System Stars for more on these).
Freewheel/cassette model
Model of a cassette — a system of rear wheel gears — mounted on a bicycle. Cassettes of different models differ in characteristics and can belong to different classes — from entry-level to professional. Knowing the cassette model, you can get acquainted with its features in more detail (according to official documentation, reviews, user reviews, etc.). This is especially important when choosing a bike for professional cycling.
Rear derailleur
Model of the derailleur (derailer) installed on the rear wheel cassette as standard on the bike. For more information on why you need to know the model of a particular bicycle component, see paragraph "Cassette Model".
Shifter model
The model of the shifters (see “Shifter type”) that are fitted to the bike as standard. For more information on why you need to know the model of a particular bicycle component, see paragraph "Cassette Model".
Chain model
Model of the chain supplied as standard with the bike. For details on the value of the Model parameter for any part, see Cassette Model
