Why Won T My Front Derailleur Shift. I take apart a trigger shifter and show the most common reason why old shifters wont shift. Front derailleurs may cause sluggish or inaccurate shifting because A the derailleur body is not positioned properly B the derailleur limit screws are not adjusted correctly C the mechanism is dirty or D the cable is damaged or improperly tensioned.
Chain shifts slowly or not at all to largest front chainring. There are a number of possible causes and you should do a little study regarding trouble-shooting the various malfunctions that your bike can have Usually and most often its that the cable has stretched. I ran into a problem where the front derailleur would shift up to the big chainrings fine but then wouldnt shift back down to the lower gears.
So to elaborate a bit more.
Alternatively your gear cable may be. Firstly shift your chain to the 2nd largest crank and the smallest cog. Set the shifter to low. On the body of your front derailleur you should find two limit screws labelled H and L.
