I’ve used 105 and Ultregra triple STI triples for ages without issue. I’m pushing them way past the limits that Shimano says you can. My touring bike (not “vintage” but it is a classic 2010 Cannondale T1) has a 46/34/20 crank tied to an 11-36 9 speed cassette. And shifts wonderfully in any gear combination. I’ve never had any issues with setting up or using STI triples on my bikes (I have 3 with STI).



You made a good choice on going to a different Shimano front derailer. Shimano’s expensive derailers are too clever and the cleverness makes them difficult to set up. The cage for the derailer is narrower than their cheaper models and thus less forgiving. The cheap deriailers (Tiagra and down) are wider and less fussy about set up.

The front derailer on the one above is a Claris or Sora. It works just fine with a 46 tooth chainwheel. It will even work with a 44 tooth chainwheel.