There are few feelings more dispiriting than shifting gears in anticipation of launching a big attack or stamping up a climb only to have your front derailleur unceremoniously dump the chain, leaving you with legs spinning but a bike that’s going nowhere. Less dramatic but almost as irritating is the rasping and grinding of a front derailleur that’s slightly out of whack. Sensitive to small changes in position and cable tension, they can require frequent attention. However, an unhappy front derailleur needn’t mean a trip to the bike shop – just follow our tips to get it running smoothly again.
Time taken: 20 minutes
Workshop saving: £10
Adjust to the correct height
The front derailleur should run parallel to the chainrings. If it doesn’t, loosen the bolt attaching it to the frame and twist it into the correct position. When directly above the large chainring, the outer edge of the derailleur should sit 2-3mm above the teeth of the chainring. If necessary, shuffle it up or down before retightening the bolt.
Limit screws
Shift into the smallest front chainring and largest rear sprocket. Of the two screws on top of the derailleur, the one nearest the frame usually controls the lower limit. This dictates how close to the frame the derailleur can move. Adjust it so the inner plate sits just clear of the chain. Spin the crank to check the chain isn’t catching.
Cable tension
Disconnect the cable attached to the derailleur at the anchor bolt. Pull the cable as tight as possible with your fingers and retighten the anchor bolt. Try to shift up to the larger chainring. If the chain won’t shift or feels sluggish, twist the inline barrel adjuster further up the cable (turn it anti-clockwise) to increase the tension and try again.
Shifting
The second screw on the top of the derailleur controls how far outwards it can move. It may be necessary to back it off to allow the chain to reach the big ring. Once engaged on the largest ring, adjust the screw so the derailleur can move no further than 1mm past the chain. This will ensure the chain can’t over-shift and fall off.
Fine tuning
With everything now locked in position, try shifting through the gears. Use the barrel adjuster to fine-tune the position of the derailleur. Turning it anti-clockwise will increase the tension, making it shift into the big chainring more readily. Don’t forget to shift across the rear cassette as well to make sure each individual gear combination works.
Derailleur trim
Riding with the chain in the smallest sprocket and smallest chainring, or biggest chainring and biggest sprocket, will wear out your drivetrain. On Shimano systems, it’ll also cause the chain to rub the derailleur. Shimano shifters have a built-in half-click (press the lever half way) to allow small adjustments on the move, known as trimming.