Learn how to index your front derailleur by following these steps and watching the video.
- 5mm Allen Key
- Phillips Head Screwdriver
Start by loosening the bolt which clamps the front derailleur to the frame, so that the derailleur can be moved by hand.
The first positioning adjustment needed when setting the derailleur up is that when the chain is on the small chain ring on a double chainset or on the middle chain ring on a triple, the outer plate of the derailleur should be 2mm to 3mm above the top of a tooth of the large chain ring. This can be checked by using a 3mm Allen key and placing it between the bottom of the outer plate and the top of a chain ring.
If any adjustment is needed to meet the clearance required, the derailleur should be able to be moved by hand as it is only loosely nipped on to the frame.
Once the height of the derailleur is set, the next positioning adjustment is to check that the outer plate of the derailleur is square to the chain ring.
If any adjustment is needed to make the derailleur square, make sure that the height of the derailleur has not been altered. The derailleur can then be tightened to the frame.
next adjustments to be made or checked are the limit positions. The low limit screw on the front derailleur adjusts the inside plate in relation to the smaller bottom chain ring. To set the lower limit position change the rear gears into the biggest sprocket on the cassette. In this position, there should be a gap of 1mm between the inside plate and the chain.
To adjust the lower limit, adjust the L-screw in the clockwise direction to move the front derailleur away from the frame, and to move the front derailleur into the frame screw the L-screw anti-clockwise.
To set the high limit position, change the rear gears to the smallest sprocket on the cassette and manually push the front derailleur over the big chain ring or pull the gear cable to force the derailleur across. Once again there should be a 1mm gap between the chain and the outer plater on the front derailleur. To adjust this high limit position, use the H-screw to move the outer plate to give the correct clearance between the outer plate and the chain.
By turning the H-screw clockwise the outer plate will move in towards the chain reducing the gap, and vice versa, screwing the H-screw anti-clockwise will move the outer plate of the derailleur away from the frame and give a bigger gap between the chain.
The next step is to check the cable tension. If the cable tension is not correct, the front derailleur will not index up to the big chain ring correctly. When the cable tension is correct the front derailleur should index all the way up to the high limit position that was set on the previous step. To adjust the cable tension, use the barrel adjustor on the down tube of the frame. To increase cable tension, unscrew the barrel adjustor so that more thread can be seen on the adjustor, this will take up any slack in the cable.
Adjust the barrel adjustor in stages whilst trying to index the front derailleur after each adjustment to check if the front derailleur is indexing correctly.
Finally run through all the gear combinations on the bike to check there is no rubbing and that the front derailleur is operating correctly.
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This repair has been carried out on a component from a popular brand. If you are using a different component please refer to the manufacturers manual to ensure specific details of the component/task are known. The principles and general skills of the task can be transferred but maybe not the exact details.