How to adjust the front derailleur?

Through previous articles, we learned how to adjust the rear derailleur. In this article, we mainly focus on the front derailleur.

Crankset and chainring parts

Front derailleur adjustment mainly refers to adjusting the H screw and L screw, as well as the micro-adjustment knob of the shifter. The H screw limits the outermost position that the outer derailleur guide plate can reach when the chain shifts to the high-speed gear, which prevents the chain from breaking away from the large chainring. In contrast, the L screw limits the chain shift to a low-speed gear and the innermost position that the inner derailleur guide plate can reach when the chain shifts to a low-speed gear. It can prevent the chain from breaking away from the small gear plate. The micro-adjustment knob is mainly used to adjust the tension of the transmission line to make the shift smoothly.

H and L screw locations

1. Adjust the L screw

(1) Adjust the chain to the smallest front chainring and the largest rear sprocket. 

(2) Unfasten the screw of the transmission cable and loosen the cable.

(3) Turn the L screw counterclockwise to allow the front derailleur to move freely, then turn the L screw again to make the distance between the inner derailleur guide plate and the chain approximately 0 to 0.5 mm.

The relative position of the inner derailleur guide plate and the chain

(4) Tighten the transmission line, move the shift lever to the position which corresponds with the smallest gear, turn the micro-adjustment knob clockwise to the tightest position, and finally turn it counterclockwise 1/4 circle.

(5) Tighten the transmission cable and fasten the locking screw.

2. Adjust the H screw

(1) Adjust the rear derailleur gear to the smallest sprocket. 

(2) Turn counterclockwise to loosen the H screw. 

(3) Turn the crank, and shift the front derailleur to move the chain to the large chainring. 

(4) Tighten the front derailleur shift cable and turn the H screw to bring the front derailleur outer guide plate closer to the small chainring until it is approximately 0 to 0.5mm away from the chain.

The relative distance between the front derailleur outer guide plate and the chain

(5) Try to shift to all gear combinations and ensure that the chain does not fall off to the gap of the frame and the chainring or fall off to the outside of the chainring when shifting. 

3. Common Questions

(1) How to adjust if chain drop off

Drop off to the crank side: Turn H screw clockwise. 

Drop off to the BB side: Lock the cable. If it does not work, turn the H screw counterclockwise.

(2) How to adjust if it is difficult to shift

Difficulty shifting from the smallest chainring to the largest chainring: Tighten the cable, if it does not work, turn the H screw counterclockwise, if it still does not work, turn the H screw clockwise

Difficulty shifting from the largest chainring to the smallest chainring: Tighten the cable, if it does not work, turn the H screw counterclockwise.

(3) What can we do if the cable shrinks in the cold weather and the front derailleur fails?

a. Check the wire

If the wire is aged or damaged, replace it in time

b. Adjust the limit screw

Loosen the L screw a little to increase the length of the cable to reduce the tension, then re-tighten it.

c. Increase the stroke of transmission. 

Special tools are required, and it is recommended to go to a bicycle shop for adjustment. 

d. Use special antifreeze lubricant

(4) No matter how we adjust the limit screw, the front derailleur has no response. How do we solve this problem?

You can first check whether the tail hook is deformed. If not, check whether the limit screw is over-tightened, then loosen the wire and tighten it. If nothing improves with the above methods, you can go to a bike shop for professional help.

(5) How to solve the chain rubbing on the front derailleur?

Check whether the front derailleur spring is working properly, if it rebounds normally, it should be possible to rule out the problem of the front derailleur itself. Move the position of the front derailleur slightly on the seat tube so that there is a gap between the chain and the inside of the front derailleur at the initial position.

Don’t hesitate to leave a message if you have anything to share. We are looking forward to your idea and story.

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References:

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

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