Bike Gear Shift Adjustment Rear Sprocket

Internal switching mechanism

City bikes often use an internal gearshift mechanism that is hidden inside the rear planetary hub (for example, the new Forward Surf 2.0 cruiser). Planetary hub bikes have only one chainring and one sprocket. The number of speeds / gears of the planetary bushings is usually from 3 to 7. The planetary hub has a rather complex internal structure.

Pluses of planetary bushings: they withstand adverse weather and road conditions well, since the mechanism and all its parts are enclosed in a case and, as a result, are reliable and durable; you can switch speeds without pedaling.

Cons of planetary bushings:. heavy weight;. very difficult repairs, impossible in field conditions.

What is gear shifting

The essence of switching speeds is to drag the chain from one star to another. Various combinations of front and rear sprockets allow you to regulate the cyclist’s load. But first, let’s turn to the bike drivetrain.

The transmission is all the parts and assemblies of the bicycle that provide the transfer of energy to the rotational movement of the rear wheel. The transmission consists of a carriage, a system of connecting rods, a chain, sprockets or cassette (or ratchet), front and rear derailleurs, as well as shifters (they are also sometimes called shifters).

Gear shifting occurs through the shifters located on the steering wheel. Using the rear derailleur shifter, located on the right handlebar, the chain is thrown between the rear sprockets, and using the front derailleur shifter (it is on the left on the steering wheel) between the front sprockets.

Most multi-speed bikes have three drive sprockets and six to eight driven sprockets. The fore stars are counted from small to large, and the rear stars, on the contrary, from large to small.

bike, gear, shift, adjustment, rear, sprocket

How to Adjust your Shimano Rear Derailleur | #CGT. Bike School

Correct star combinations

Choose speeds based on the terrain and your physical capabilities, and so that the chain does not tilt. You can make sure that there are no distortions simply by looking at the chain. If it moves parallel to the frames of the front derailleur, then the selected speed is optimal. Skew occurs when the chain is on the front large chainring and the rear chainring is also large.

Let’s see which sprocket combinations are applicable for a bicycle with three chainrings and eight chainrings. The main principle is simple: it is necessary that the combination of front and rear sprockets is always approximately in the same vertical plane.

The large chainring is matched with 4-8 rear chainrings. This combination is optimal when riding on a flat road.

The middle chainring is matched with the 3rd to 6th chainrings. This combination is suitable if you are riding on lightly rough roads, or if you want to give yourself more physical activity while riding on a flat road.

The small chainring is matched with 1-3 rear chainrings for uphill climbing. In this case, much less effort is required from the cyclist when pedaling, but more frequent pedaling.

Incorrect combination of front and rear sprockets, leads to a strong misalignment of the chain, shortening the life of not only the chain, but also the derailleurs.

What to do if you can’t adjust the bike’s rear derailleur

If you have followed all the previous points correctly, but you still did not manage to adjust the correct reverse gear shifting, then there is another way to adjust the shift. It is mainly used to tune heavily worn rear derailleurs or, if the latter is the most budget level. In principle, most of the actions repeat the above method, but there are still differences.

  • We remove the chain. Switch back to the smallest star and fold the gearshift cable.
  • We tighten the cable tension adjustments as described above in paragraph 3.
  • We adjust the extreme position H similarly to the previous method, except that the plane of the rollers is shifted away from the wheel (to the right, when viewed from behind) by a minimum distance, literally 1/10 mm.
  • Then, without throwing up the cable, by hand we shift the parallelogram towards the largest star of the cassette and adjust the extreme position L. The plane of the rollers, relative to the largest star of the cassette, is shifted by 1/10 mm towards the spokes (to the left).
  • After you have set the extreme positions of the switch (low and high), put the chain in place and set the largest star in the front and the smallest star on the back of the switches.
  • Then we carry out points 5, 6, 8 and 9 from the method of setting the rear derailleur, which is described above.
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The second method helps you to more accurately set the extreme positions of the bicycle derailleur, since the chain does not bother you. And small offsets in the L and H tuning can solve the switching problems of old crossovers, where there are slight backlashes. The main thing is not to overdo it with the displacement of the plane, because this could cause the chain to kick off. If you are unable to adjust the rear crossover by either the first or the second method, then most likely your cock or switch foot is bent (or the crossover is out of order). What to do with this is described at the preparation stage. There is a possibility that the problem is not in the derailleur, but in the breakdown of the shifter, which does not allow you to switch speed clearly.

If you do not understand something from the instructions on how to set up the rear derailleur, you can watch this video, which will clearly show what to do and in what sequence.

What is gear shifting for?

Riding on a flat road, uphill or downhill requires different efforts from the cyclist. On a single speed bike, there are no options, since there is only one gear. And those who have experience riding a single speed bike know how difficult it is. But in the case of a multi-speed bike, new possibilities appear. you can adjust the load. On a bike equipped with multiple gears, for example, it is much easier to ride uphill. Let’s figure out how the gearshift occurs.

Preparing to set up

Before we move on to setting up the derailleur, we need to make sure that it is properly installed on the frame:

First, the derailleur frame should be 2 millimeters above the teeth of the largest chainring (see photo below).

Secondly, the frame must be strictly parallel to the chainring block of the bicycle.

The switch must be washed and lubricated before adjusting (just drop a drop of grease on all moving joints). It is also necessary to clean the drive cable and “jackets” from dirt. If the cable is worn out, replace it.

Move the chain to the largest sprocket in the back and the smallest in the front.

The shifter has a drum for adjusting the tension of the drive cable. This drum must be scrolled clockwise without twisting two or three turns to the stop.

Loosen the screw that secures the drive cable.

Design and principle of operation of the rear cross-over

Bicycle rear derailleur designs from Shimano, SRAM, or other manufacturers (such as SunRace) are not particularly complex or highly adaptable. The crossover is a set of the following nodes:

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    Attaching the switch to the cock. Place with bolt hole. Using this assembly, the switch is installed on the bike (bolted to the cock).

The principle of operation of the rear derailleur is quite simple. When you change the speed limit on the shifter (which is located on the steering wheel), the gear shift cable is pulled or loosened. Since it is rigidly fixed with a fixing bolt to a spring-loaded parallelogram, this causes the latter to shift towards the larger star, when the cable is pulled (with decreasing speed), and to a smaller star, when it is weakened (with increasing speed). When the cable is loosened, the spring provides the parallelogram displacement. Changing its position, he shifts the foot with a guide roller and a tensioner roller in the direction we need. The latter, deflecting back under the influence of the spring, removes the chain slack, which improves the switching accuracy. The guide roller shifts the chain to the desired star, which, clinging to the small protrusions on the sprocket, jumps to it (this is if there is a switch from a smaller star to a larger one, if on the contrary, the chain simply jumps from a larger star to a smaller one).

I would like to note that the movement of the parallelogram occurs not in one plane, but in several, because he needs to compensate for the different diameters of the rear system stars (the chain tensioner serves the same compensation).

It should also be said that this is how most rear derailleurs (except planetary) work, regardless of the manufacturer (Shimano, SRAM) or the number of speeds (6, 7, 8, 9, 10, etc speed systems)

You can clearly see the principle of operation of the rear derailleur in the video.

To adjust the gear shift, you will need the following tools:

Basically, shifting adjustments are made after careless cyclists begin to continuously shift from low to high speeds at once, resulting in the normal chain jumping over multiple sprockets. Our people sometimes do everything with the masters, this is to some extent true, but on the other hand, it is real and independent to adjust the gear shifting devices. Rear derailleurs have forward and reverse thrust.

Cable attachment (rear)

Attaching the end of the cable to the derailleur bolt often causes problems. If it is approached at the wrong angle, the geometry of the parallelogram will be distorted and therefore it will be difficult to achieve normal derailleur movement throughout the gear range. The switch usually has a groove or washer with a curved end to indicate that the cable is attached correctly.

For example, on the derailleur pictured above, the cable is not properly attached. You can see the groove between the cable and the bend in the washer.

Adjusting the screw “H” of the front derailleur.

  • Switch to outer rear sprocket and outer driving chainring (see first and second photos).
  • Pull the cable by hand to make sure that the “H” screw does not affect the speed selector (see photo).
  • While keeping the cable taut, check the clearance between the chain and the outer retainer plate. It should be about one millimeter (see photo).
  • Pedal your bike slowly, observing the clearance. Achieve the required clearance by adjusting the screw “H” where the drive sprocket is closest to the chain during rotation.
bike, gear, shift, adjustment, rear, sprocket

External Shifting on Speed ​​Bike

The outer type belongs to most multi-speed bicycles. It is used on both mountain and city walking models. The mechanism is made up of gear shifters and stars that form a cassette or system. Variable speed with rear and front derailleurs.

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This type of gear shifting can be seen on both the Forward Dortmund city bike (7 speeds) and the Forward Agris mountain bike (24 speeds). You can customize this switch yourself by examining the mechanism.

Preparing to set up

Before we move on to setting up the derailleur, we need to make sure that it is properly installed on the frame:

First, the derailleur frame should be 2 millimeters above the teeth of the largest chainring (see photo below).

Secondly, the frame must be strictly parallel to the chainring block of the bicycle.

The switch must be washed and lubricated before adjusting (just drop a drop of grease on all moving joints). It is also necessary to clean the drive cable and “jackets” from dirt. If the cable is worn out, replace it.

bike, gear, shift, adjustment, rear, sprocket

Move the chain to the largest sprocket in the back and the smallest in the front.

The shifter has a drum for adjusting the tension of the drive cable. This drum must be scrolled clockwise without twisting two or three turns to the stop.

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Loosen the screw that secures the drive cable.

Switch classification

In the modern world, there are many companies that create equipment for bicycles. The best quality models are made by corporations such as Shimano (Japan) and Sram (America), which make complete derailleur mowing lines.

  • Shimano XTR, Sram ESP 9.0 and Sram ESP X.0 are leading the way in price and quality. They are mainly used in competition bicycles. They are characterized by low construction weight.
  • Shimano deore xt, Shimano Saint, Shimano slx finished second in the same category. Used in bicycles with 27 gears.
  • Shimano Deore LX, Shimano Dura-Ace, Shimano Hone. 3rd place. They are designed for devices with the maximum number of speeds.
  • Sram ESP 7.0 and Shimano Deore are similar designs. Made from highly durable components and designed for 24 gears.
  • Sram ESP 4.0, Sram ESP 5.0, Shimano Nexave and Shimano alivio are cheaper than the professional line. They can handle up to 24 speeds and are designed for touring bike models.
  • The Sram ESP 4.0, Shimano C201 and Shimano acera are bundled with the cheaper entry-level hybrids and mountain bikes. Withstand up to 24 gears.
  • Sram ESP 3.0, Shimano Nexus and Shimano altus are designed for touring, city bikes.
  • The Shimano tourney is built for a calm, smooth ride. Shifts 21 gears.

There is no fundamental difference in the adjustment and operation of different switch lines from the same company. For example, different Shimano derailleur groups work the same and are interchangeable. Let’s say that the drive of eight-speed Alivio, Altus, Acera switches can be equipped with nine-speed Deore, Deore XT, Deore LX, XTR systems and vice versa.

Types and design of switches

Today, there are three types of speed switches:

  • external;
  • internal;
  • combined.

Beachbikes.com. How to tune a 7 speed bicycle (adjusting a derailleur)

Most often, modern mountain bikes are equipped with systems related to external shifting, in such mechanisms the gears are shifted using two switches (front, rear). And on city models, internal gearshifts are often installed. The combo system is the average option, often found on road bikes.