Originally Posted by Grasschopper
Tiagra - the next step up - gets the 9th gear and moves to a shifter more like the rest of the Shimano line with a paddle behind the brake lever.
105 - the sweet spot in the Shimano line. For 2006 it has gone to the 10 spd and has the same mechanism design as Ultegra and DA but is a bit heavier. Crank gets the external BB design which you find now at all levels here and higher.
Is Shimano phasing out their 9-speed 105 line? I noticed that they were all on sale this season, and I was thinking about one day upgrading my Tiagra components to 105. If the 9-speed 105 components are going to be discontinued, should I buy those parts now?