Here is the procedure to mount and adjust you front derailleur, and to set it up properly. The three feature are proper position of the derailleur on the seat tube, proper cable tension, and proper setting of the limit screws. It should be mounted properly. Cable tension can be adjusted at the derailleur, and then fine tuned at the handlebar on the left shifter. The limit screws (inner and outer) need to be identified and set properly. 1) To Mount: Position the angle of the front derailleur on the seat tube with a 5 or 8mm hex Allen wrench so that it is lined up and parallel to the chain. This is the rotation when mounting the derailleur. The height is adjusted when the outer cage has about 2mm vertical clearance from the teeth on the outer chainring when it is moved above it 2) To Adjust the Limits: The Limit screw adjustments prevent the derailleur from throwing the chain to the inside our outside of the chainrings. These are labeled "L" for low gear (small chainring) and "H" for high gear (big chainring). The "L", or inner adjusment , is located closer to the frame, and the "H" is furthest from the frame (except Shimano XTR is opposite). To verify which is the "L", put the chain on the inner chainring and tighten the limit screw. If it moves the front derailleur outward away from the bike it is the "L" screw for sure. "L" screw adjustment>> Shift between the middle and low chainrings while bike is on stand or upside down. If the chain drops off the inside of the inner chainring, then tighten the "L" screw about 1/4 turn and try again. If the chain does not easily drop onto the inner chainring, then loosen the "L" screw about 1/4 turn and try again. "H" screw adjustment>> Shift the chain back and forth between the middle and outer rings. If the chain jumps over the big chainring to the outside, then tighten the "H" screw about 1/4 turn and recheck. If the chain will not make it on to the outer chainring, loosen the "H" limit screw about 1/4 turn and repeat. 3) To Adjust the Cable Tension: With the chain on the small chainring, remove any slack in the cable using the handlebar adjusters or the cable fixing bolt on the derailleur. Check that the cable is loose enough to allow the chain to shift smoothly from the middle to small chainring. If it is too tight, it may not go to the inner ring. Check that the cable is tight enough so that the derailleur starts to move as soon as you move the shifter, and will be tight enough to move the chain to the largest chainring. 4) Fine Tune: There can be a couple of problems with the front shifter. Most often it is the cable tension, and can be adjusted at the handlebar barrel. This is your fine tuning. Make sure the chainring teeth are not worn or bent. Check the chain for bad links. Check that the cage is not bent or loose on the seat post. If it rubs a little while pedaling, adjust the cable tension a little at the handlebar barrel, or maybe check the limit screws (rarely necessary). Check for proper spacing between the chainrings, and that you have the right chain for your bike (8 spd. or 9 spd.) Lube your cable. That's about it! |
