Join Date: Jul 2005
Location: Boulder County, CO
Bikes: '79 Gios, '80 Masi, '06 Felt, early '60s Frejus
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Sounds like the problem is too much tension on the cable, jamming the cage up against the limit screw. The ratchet that works for the downshift paddle needs a less tension.
Loosen the cable tension, then tighten just so you can hit the big ring consistently and get a bit of movement for the trim position. On your small ring, the cable will actually be slack. If the cable needs to be so tight that you can't get onto the small ring, loosen the outer limit screw a bit, but not so much that you drop the chain.
Also make sure the cable is routed correctly in the shifter and the derailleur cage is properly aligned. True, 105 front shifters are not as smooth or durable as Ultegra, but when properly set up they are more than adequate.