ypsetihw

I've searched and read a lot - maybe this post is just to tell you what I'm going to attempt and to log my results for the rest of the web.

What I had: FSA Omega 50/34, BB4000 English - 105 5800 FD/SS RD 105 11-28
Advertised Specs: 16T max drop, 28t max advertised, 33 total tooth max capacity

What I'm running: DA9000 52/36, BB9000 English - 105 5800 FD/SS RD 105 (12-28) (built from 5800 11/-28/12-25)

What I'm going to run: DA9000 52/34, BB9000 English, 105 5800 FD/SS RD 105 12-28 [running 18T drop on 105 5800 FD Mechanical on 105 12-28 cassette, being careful not to crosschain]
Actual Specs: 18T max drop, 28t max advertised, 34 total max capacity

I don't think the 34 tooth total will be an issue at all, especially because I don't cross chain, and never beyond 2 cogs., and I'm sure Shimano designs a cog or two of error into their posted specs. I will have a compact low gear (34/28) and a nearly standard high (52/12), with a crazy range, with over 40mph+ of top end for leadouts and downhills and a modest low gear for climbing. Given this setup, a front change would be accompanied by 4 gears on the cassette, which is more than 1 throw, but doable. I've ready in detail that the new 2015+ 105+ can easily take 18T up front. Carefully conducted, this setup could probably also utilize a 12-32 .

I'm not only certain this can be done, I'm wondering why Shimano doesn't come out with something incredible and drastic, like the 46/30 13-32, which in my opinion, would absolutely crush the commuter and touring market. It could go anywhere and almost NEVER exceed the drivetrain in any situation.