Adjustment of the top normal derailleur

In previous articles, we have a preliminary understanding of the transmission system (A brief discussion on the transmission system). In this article, let us have a more in-depth understanding of top normal derailleur which is the important component of the transmission system and learn how to adjust it. 

Before discussing the key points, we need to know under what circumstances the rear derailleur needs to be adjusted.
The common case is when there is a loud friction sound in the rear derailleur system, the chain jumps up and down, the chain often falls off, the gear shifting is inaccurate or a new derailleur is installed. You need to adjust the derailleur if you meet the above cases. 

The following adjustment methods are mainly for the top normal derailleur. 

1. Adjust the position of the small flywheel

(1) Adjust the chain to the smallest flywheel and maximum crankset, unfasten the rear derailleur cable locking screw, and completely loosen the cable.

The relative position of the flywheel and chain

(2) Make sure the smallest flywheel, chain, and guide wheel are aligned, and turn the high-speed limit screw (marked ‘H’) until the middle of the guide wheel is aligned with the outer edge of the smallest flywheel.

The relative position of the guide wheel and the smallest flywheel

(3) Tighten the derailleur cable and shift gear to the highest speed. Turn the cable tension adjustment knob on the shifter or the knob on the derailleur clockwise, then turn it 1/4 counterclockwise.

Adjusting the shifter

(4) Put the cable into the lot of the derailleur locking screw, then tighten the cable, after that fasten the locking screw with 5 to 6.8N/m torque.

Adjust the locking screw

2. Adjust the position of the large flywheel

(1) Turn the rear low-speed limit screw (Marked ‘L’) counterclockwise until the guide wheel is free to move to the maximum flywheel.

Position of limit screws

(2) Move the chain to the smallest front sprocket and the largest flywheel.

Move to the largest flywheel

(3) Turn the limit screw (Marked ‘L’) clockwise and move the guide wheel outward until the guide wheel is limited and can only reach a position aligned with the centre line of the largest flywheel.

The relative position of the guide wheel and the largest flywheel

In conclusion, the derailleur can be initially adjusted by adjusting the high-speed and low-speed limit screws. However, further inspection and commissioning are required if you want to adjust it quickly and accurately. The following steps can be referred to. 

3. Commissioning 

(1) Move the chain to the largest front crankset and smallest rear sprocket.

(2) Shift once, making sure to move smoothly to the penultimate flywheel. If there is too much noise when shifting or the gear cannot be shifted, turn the cable tension fine-adjustment knob counterclockwise, change the gear again, and make sure the shift is smooth. If the chain moves to the third flywheel, turn the cable tension fine-adjustment knob clockwise until the guide wheel is aligned with the penultimate flywheel. 

(3) Press the shifter halfway to tighten the cable without shifting to the next gear, and turn the crank simultaneously. If there is a slight sound and the chain does not jump to the third flywheel, it indicates that the fine adjustment is successful. If there is no sound, continue to adjust the fine-adjustment knob. 

(4) Continuously shift gears to ensure shifting accuracy. If it cannot be adjusted slightly, adjust the fine-adjustment knob of the cable until the chain can shift accurately.

Thanks for watching. 

Don’t hesitate to leave a message regarding the adjustment of the rear derailleur if you have anything to share. We are looking forward to your idea and story. 

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YouTube: https://youtu.be/kW-v0ydDtro

References:

[1] ‘Cycling Bible’ Editorial Board. Cycling Bible [M]. 1st Edition. Beijing: Machinery Industry Press, 2013.

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