Join Date: Jul 2000
Bikes: 1959 Capo; 1980 Peugeot PKN-10; 1981 Bianchi; 1988 Schwinn KOM-10;
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 141 Post(s)
The diagnosis is simple. If the cable is always under tension, even in low gear, then it is keeping the cage from swinging far enough inward to effect the 2->1 gear change. If the cable goes slightly slack, then the cage motion is probably being limited by the L adjustment screw, which needs to be backed out a bit. Another possibility is that the front derailleur is either bent or misaligned.
Step 1: Make sure the cage is parallel to the chainrings. With a bolt-on (rather than old-fashioned clamp-on) derailleur, you may need to replace the unit and/or straighten the frame's braze-on.
Step 2: Make sure you have a bit of cable slack in low gear. If the cable projects past the fixing bolt and nut, you can loosen the nut to cut yourself a bit of slack. (It sounds as though turning the adjusting barrel is lengthening your housing, and therefore effectively tightening your cable.)
Step 3: If the cage still does not swing far enough inward, try turning the L screw anti-clockwise. If this does not permit the cage to move farther inward, check the derailleur for damage, stiffness, or perhaps a weakened return spring.
Good luck. Let us know what you discover.
"Early to bed, early to rise. Work like hell, and advertise." -- George Stahlman
Capo [dschaw'-poe]: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger, S/N 42624
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1981 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069