Front derailleur

'Front Derailleur Adjustment'

General: The first thing to do in getting front derailleurs to work well is to clean and lubricate everything involved in the shifting of the chain among the front chainrings as well as the chainrings themselves. Everyone has their own preferred way of cleaning, and any method that does not damage the parts or make the adjustment job harder is a good one. I recommend getting up close and personal with your shifter, cable, and derailleur with a good, clean rag from time to time before making adjustments. Your time spent adjusting will be much more meaningful and long-lasting if you first clean things up.

Note about loosening things: Unless you have a full day to spend working on your bike, I strongly suggest leaving things (shifters and derailleurs) in their current "bike shop" position unless you must move them. This especially applies to the front derailleur. It was (hopefully) mounted in the correct position on the seat tube when it came assembled from the bike shop. In most circumstances, there is no adjustment to ever make here unless you need to replace the whole derailleur. If that is not the case, then just leave it and clean it where it is attached to the bike. However, if you need to make a position adjustment, make sure that the chain guide plates are parallel to the chainrings and that the clearance between the chain guide outer plate and the highest point of the largest chainring is 1 to 2 mm. Some expensive Shimano derailleurs (XTR) mount to both the seat tube and the bottom bracket, and there is no vertical or lateral adjustment to be made to these derailleurs. Consequently, you must use the chainring sizes intended to be used with these derailleurs, so make sure you always replace with the same sizes you originally had.

Note about adjustment: The golden rule here is to not fix it if it is not broken. If shifting among your chainrings is smooth and serves your purposes, don¹t meddle with things. You may find yourself frustrated and worse-off than when you started. However, sometimes adjustment is necessary as described below.

Adjustment: There are three adjustments to make; inside limit, outside limit, and cable tension. 1.) Inside limit (low adjustment): Set the chain on the smallest chainring and the largest rear sprocket. Looking down on the front derailleur, locate two screw faces. In most cases (excluding Shimano differential-plate derailleurs, which have a reversed arrangement), the inner-most screw is used to set the lower or inside limit (how close the derailleur moves to the frame). Set this screw so that the clearance between the chain guide inner plate and the chain is 0-0.5 mm (almost touching). Turning clockwise moves the chain guide further away from the frame, while turning counterclockwise moves the chain guide closer to the frame. Make sure the shifter is in the "1" or lowest position, check the cable tension, and remove cable slack if any exists using the barrel adjustment at the shifter or by taking up slack in the cable at the clamp on the derailleur itself. Tighten the cable up to but not beyond the point at which the derailleur begins to move out of its lower limit position. 2.) Outside limit (top adjustment): Set the chain on the largest chainring and the smallest rear sprocket. While looking down on the derailleur, locate the outer-most screw. In most cases (see above), this is used to set the higher or outer limit (how far away from the frame the derailleur moves). Using this screw, adjust so that the clearance between the chain guide outer plate and the chain is 0-0.5 mm (almost touching). Turning clockwise moves the chain guide closer to the frame, whereas turning counterclockwise moves the chain guide further away from the frame. The shifter should indicate a "3" or high position. 3.) Cable tension adjustment (intermediate chainring): Set the chain on the middle chainring and on the largest rear sprocket. Adjust the barrel adjustment so that the clearance between the chain guide inner plate and the chain is 0-0.5 mm (almost touching). Using the shifter, move the chain back and forth through the entire range of gears and fine tune the action with the barrel adjustment on the shifter. Check that the cable is loose enough to allow the chain to shift smoothly and repeatedly from the middle to the inner chainring. Additionally, check that the cable is tight enough so that the derailleur starts to move as soon as you move the shifter.

Troubleshooting: 1.) If the chain ever falls from the smallest chainring towards the bottom bracket, then the inside limit screw needs to be turned clockwise (about 1/2 turn). 2.) If the chain does not move freely from the middle chainring to the small chainring, turn the inside limit screw counterclockwise (about 1/4 turn). 3.) If the chain falls off the largest chainring towards the crank arm, then the outside limit screw needs to be turned clockwise (about 1/4 turn). 4.) If the chain does not move freely from the middle chainring to the largest chainring, turn the outside limit screw counterclockwise (about 1/4 turn).