Rear Derailer Adjustment

‘B-Tension’ Screw

B-Tension screw controls the tension of the upper pivot spring. Loosening this screw (turn anti-clockwise) brings the guide pulley closer to the gears thus better shifting. But we dun want it to be too near until the pulley knock against the largest rear gear causing noise and maybe shifting problems.  Check/ adjust this when the chain is set at biggest rear gear and smallest front chain ring. Usually we’ll only need to adjust this tension when we change the chain length or size of rear gear.

 

Limit Stop Screws

These 2 screws set the travel limits, how far the derailer can move from left to right (biggest and smallest gear position). Basically we want to set the limit stop screws so that the chain does not over shift out towards the spokes or get stuck between the small sprocket and dropout. This can be done by aligning the guide pulleys to the sprockets.

Normally, this is done only when a new derailer is installed or when you change to a different rear cassette. Note: can be used as a temporary field fix for a bent deraileur.

Low Gear limit stop

 

High Gear limit stop

 

 

Shifting Adjustment (one click one gear shift)

The click-stops that provide indexing are in the shifters. It sets the length of the cable so that the derailer moves to the correct position/gear to correspond with each shifter click. If a derailer is correctly adjusted when it is installed, this is the only adjustment that should have to be fine tuned overtime to accommodate cable stretch, or when cables are replaced.

Fine adjustment of the indexing can be done using the adjusting barrel located at one end of a length of cable housing. There is also another index adjuster at the shifter itself, just where the cable exits. This allows the rider to do fine adjustment when on the move. Enough bla bla bla …. so how to fine tune.

1. First start with shifter at home position and chain on the smallest gear. Always start adjustment from the small rear gear and big front chain ring.

2. Click the shifter to the first click after the fully loose home position, then turn the pedals forward. The chain should shift to the second smallest gear. If it doesn't, it means the cable is too loose.

3. Turn adjusting barrel counter-clockwise (CCW) to tighten the cable. Start with half a turn, then check again. Repeat until it moves up to 2nd gear.

4. If derailleur fails to shift to next gear after several rounds of the barrel, inner wire may be too slack. Turn barrel adjuster (CW) fully into derailleur body then turn counter clockwise two turns to allow for index adjustments. Loosen inner wire anchor bolt and gently pull on inner wire with a plier to remove slack. Tighten inner wire anchor bolt.

5. After it moves up to the 2nd gear, turn the pedal slowly, observe and listen. Chain may be jumping on the gears at this stage if the cable is still not tight enough (same if over tension). Give it another 1/4 CCW turn a time to stop the jumping. You should hear chain rubbing tick tick noise. Tighten cable until the noise is gone. Continue to tighten 1/4 CCW turn until you get a over-tighten noise.

6. Once the too-tight noise is achieved, turn barrel adjuster 1/4 turn clockwise, to release wire tension, and pedal again to check for no tick tick noise. Continue turning barrel adjuster 1/4 turn clockwise until the noise stops.Viola!

   

    

• Click shifter back and forth between home and 2nd gear while slow spinning the pedal to check for smooth up and down shifting. When you’ve got it right, the rest of the gears should also shift smoothly. Shift lever to change gears, and check that no noise occurs in any of the gear positions.

• If you think you’ve way over tighten or totally mess it up, no worry. Just start over. Remember to shift to smallest gear and set the barrel adjuster to a neutral position (turn barrel clockwise all the way in and back up 2 rounds to give some allowance) before you start over. Unless your cable tension is totally messed up i.e. out of range using the barrel adjuster, we dun need to touch the anchor bolt in step#4 above.

• Fine adjustments are accomplished according to the following principles:

  • Shifting from small to larger sprockets is accomplished by tightening the cable; if such shifts are slow, the cable is not tight enough--turn the barrel counterclockwise to tighten it.

  • Shifting from big to smaller sprockets is accomplished by loosening the cable; if such shifts are too slow, the cable is not loose enough--turn the barrel clockwise to loosen it.

  If the rear indexing works properly when using the large chain ring but not on the small chain ring, or vice-versa, this is often a sign that the rear derailer hanger is bent.

NOTE: Here assumes that there are no unusual problems, such as bent derailleurs,  or excess inner wire friction from dirt in the housing, or modified components.

 

Adapted from various online resource. Source1

 

Afternote:

1. Tuning done but only the 7th gear is having noise. What do I do now?

This may not be the right way but it works for me:

Check if cable needs more tightening: At the 7th gear noisy position, spin pedal slowly. To simulate cable tightening, lightly finger press the RD inwards, or lightly finger pull the exposed inner cable  along the top tube. I prefer the finger pressing more because I get to feel the rubbing when cable is over tighten.

- If noise disappear, cable needs more tightening. Turn Barrel 1/4  CCW until noise disappear.

- If you get more rattling and noise, cable needs loosening. Turn Barrel 1/4 CW until noise disappear.

Run thru all the gears again and re-adjust if required. Good luck and have fun.