Join Date: Jul 2000
Bikes: 1959 Capo; 1980 Peugeot PKN-10; 1981 Bianchi; 1988 Schwinn KOM-10;
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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