Cornucopia of Awesomeness
Join Date: Oct 2004
Location: not where i used to be
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
outboard bearings don't screw with the chainline per se, it's just that the chainline isn't adjustable by simply using a different length bottom bracket.
That Truvativ crank, presumably was designed to give a 42mm chainline.
Road double cranks usually position the inner ring at ~39mm and the outer at 45mm. (i've never owned a crank with external BB cups, so i don't know if this convention is still the case) In the days of square taper cranks, you could adjust chainline by simple changing your BB spindle length. However, since on your 105's the spindle is essentially integrated into the cranks themselves you have no way of repositioning your chainrings relative to the centerline of the frame.
Now you can still work with this.
You have to install your cranks and measure the chainline of the inner and outer rings. Maybe you'll get luck and one of them will be 42mm. Otherwise you'll have to make all your adjustments to your chainline at your rear hub.