I saw your other bike buying thread and I gave you my $0.02 about buying a Trek Domane (which I have and love), and now you're here asking about Cannondale.

I have a Trek Domane and I just bought this a few days ago to use as my commuting bike. Mens 51cm Synapse Alloy 105 Disc. Braking is fine on my particular sample, no break in needed.



With regard to your question, there is no point upgrading the Tiagra to 105. I *wanted* disc brakes on my Synapse, but if it came with Tiagra instead of 105, I would have been perfectly happy. It makes ZERO real world difference.

I do have to go with the sentiment you're perhaps overanalyzing things a bit....once you get into this price range, most bikes are pretty good and anything that is not to your satisfaction can be easily changed out. In my case, the seat got tossed and I got an ergonomic seat. I'll probably adjust/shorten the height of my handlebar once I settle into it by changing the stem height and maybe the length. I might also change to a wider tire if I start taking the route that includes a bit of gravel.