The rear hub of the bicycle should always be in good condition, because it determines the smoothness of the two-wheeled transport. According to many cyclists, the driving performance of a bike depends largely on the type and mechanical performance of the frame. However, in practice, the determining factor here is the state of the chassis - bushings, carriages, chains, and other systems.
Types
According to compatibility with various types of brake systems, several separate types of rear hubs are distinguished:
- for disc brakes;
- for roller brakes;
- for rim brakes.
Of course, the more complex bicycle rear hub designed to connect to the disc brake system can easily be used to assemble wheels with rim brakes, but not the other way around.
Design
The rear hub of the bicycle includes the following structural elements:
- housing;
- flanges;
- axis;
- bearings.
Body
This component of the design of the rear hub acts as a connecting shell for other functional mechanisms. The main requirement for the body is a high rate of rigidity, since the sleeve is subjected to significant torsional loads during riding.
The rear wheel hub of the bicycle can be protected by a body made by stamping or casting. The most reliable high-strength cases are made in the first way.
Flanges
They are specific annular protrusions that are contained on the rear hub housing. This element is used to connect to the spokes of the wheel. Flanges contain special holes where knitting needles are inserted.
The main requirement for flanges is a high strength indicator. Based on the small size of the part, it is enough to imagine how much increased load falls on its share. After all, a third of the construction of the bicycle together with the cyclist is located precisely over the area of the rear flanges.
Bearings
The rear hub of the bicycle must be equipped with bearings with an antisplash cover. Only in this case it will be possible to forget about their maintenance and replacement, having rolled more than 10,000 km on a bike. Frankly poor-quality bearings will make you endure unpleasant sounds and suffer from wheel play after the first trip in rainy weather, not to mention winter. Reliable dirt protection is represented by various seals that prevent contact of the lubricant with the external environment.
Currently emit bulk and industrial bearings for the rear bushings. The difference is that you can eliminate the play in the wheel by performing the usual adjustment of bulk bearings. If there is a similar problem in the case of industrial bearings, most likely, they will have to be replaced. Therefore, the sleeve of the rear wheel of the bicycle should be selected based on the type and reliability of the bearings.
Axis
The main parameter of the axis of the rear hub is its length. To select a sleeve according to the axle length index, it is enough just to measure the distance between the opposite external nuts on the corresponding mountings of the bicycle frame.
Standards
Having studied the internal and external structure of the rear hub of the bicycle, it is recommended to pay attention to a wide range of sizes of this system. The presence of some differences in the parameters is due to the use of bushings on various types of bicycles :
- track models - 10x120 mm;
- road bikes - 10x130 mm;
- the bulk of common mountain models –10x135 mm;
- bicycles for downhill - 12x135 mm;
- professional models of the "cross-country" class - 12x142 mm;
- models of bicycles for freestyle, extreme sports - 12x150 mm;
- BMX class bikes - 14x110 mm.
Design differences
The device of the rear hub of a mountain group bicycle has some differences from the designs of the chassis for road bikes.
Bushes for road and road bike models have gaskets - special seals designed to protect bearings from contamination. Often, oil seals are combined into a single unit with conical elements.
The rear hub of the Stealth bike, as well as other common models of mountain and off-road bikes, often has rubber anthers in addition to glands connected to the cones. The presence of such elements helps to increase the protection of the running gear from dirt, all kinds of debris and dust.
Unlike the highway category of bikes, mountain models are designed to ride on the most impassable terrain. Naturally, the use of additional protection for the rear hub mechanism proportionally leads to an increase in the weight of two-wheeled vehicles and a decrease in ease of travel. That is why the assembly of the rear hub of a highway-class bicycle is carried out by most manufacturers without installing these elements.
Separately, it is worth considering the design features of bikes with disc brakes. Here, mechanisms are used whose flanges are connected to the brake discs.
Differences are also present in the methods for connecting ratchets on a sleeve with cartridge mounts. Most common domestic-made bicycle models include bushes with integrated ratchets. In contrast, the rear hub of a speed bike usually has a screw-type ratchet.
Specific features
In the predominant majority, the rear hubs are distinguished by an asymmetric design, since a cartridge or a rear sprocket should be located on the right side of the mechanism. Compared to the left, the right flange is closer to the center of the axis. As a result, the right side of the knitting needle is somewhat shorter.
There is a special type of planetary bushings. The internal structure of such products contains a gear shift mechanism. Only one star is installed on such systems. The bushings of this plan can be operated without installing a chain tensioner.
How to assemble the rear hub of a bicycle?
When starting to assemble the mechanism, it is necessary to take into account the fact that the left and right ends of the axis have some differences. The right cone tightly connects to the axis, is further strengthened by a lock nut and therefore never dismantled. The system is adjusted by changing the position of the left cone.
Trying to figure out how to assemble the rear bicycle hub, the main thing is not to confuse the side on which the axis with the right cone should be mounted. To make a mistake here is much easier than in the case of assembling the front wheel, where both sides of the mechanism look identical.
To avoid trouble by connecting the elements of the rear hub into a single unit during installation, the following sequence of actions will allow:
- To begin with, the sleeve body, ratchets and the surface of the cups for mounting the system are cleaned of contaminants, the remains of old grease, after which a new grease base of a thick consistency is applied.
- Using tweezers, the balls of bearings are placed in the right place and pressed into the lubricant layer, the amount of which should be sufficient so that the balls do not roll back.
- On the ratchet side, an axis with a right cone is installed. The operation is carried out carefully, since there is a high risk of pushing the bearing balls out of the bowl.
- At the end, the left cone is screwed almost all the way to the axis, but it is not tightened. Washers are screwed in the correct sequence, after which locknuts are attached.
On this, the rear hub is considered practically assembled. The only thing left is the installation of rubber anthers. However, it is advisable to do this only after the final adjustment of the chassis system.
Bicycle rear hub - repair
As practice shows, the most common and typical for the rear hub malfunction is excessive tightening or loosening of the cone. In the latter case, you will have to endure a noticeable backlash. On the contrary, the constriction of the cone mechanism will lead to a stiffer, more difficult course of the two-wheeled vehicle. In addition, crunching may occur in the bearings.
What to do when the backlash of the bike is causing the backlash to occur? Repair in this case will consist in tightening the cones using special wrenches. 15 and 20 mm open-end wrenches are suitable for this, with which the locknuts are first unscrewed, and then the cones are clamped or loosened to the desired limit.
Ideally, the effect of play during bicycle movement should be completely absent. If the conical mechanisms of the rear hub were adjusted correctly, the wheel will easily rotate without an additional impulse, only under the influence of attractive forces on the reflectors.
Often the cause of the breakdown is the bending of the sleeve. Most often this happens when using low-quality, inexpensive parts. If this happened, only a complete replacement of the axis with a new, more reliable one will solve the problem.
In order to carry out repairs or scheduled maintenance of the rear wheel hub, it is more convenient to remove ratchets in advance. However, when the whole essence of repair is the usual tightening or loosening of the cones, resorting to such an action is not necessary.
In the end, in order to avoid unnecessary problems in the form of prolonged downtime of the bike and waste for expensive repairs, it is enough to regularly undergo maintenance. Most often, the essence of maintenance is reduced to overhauling the mechanisms, cleaning them, lubricating and installing them in the reverse order.