So regarding STI levers, Blakey’s dad states:
Where does one find this information? In particular, the chainring sizes that work with 105SC levers…with a 600 Ultegra (tricolour) FD.
Cheers.
They’re more forgiving than you’d think.
What are you trying to run? 39-53 and similar ranges that aren’t super small/large/offset will work.
Oh okay, I’ve got a 53 big ring and I was just thinking for most of the riding I do I really don’t need it to be that big. Sounds like going down to 50 or something wouldn’t be an issue.
But how else can you do 53x11 ???
You might have 99 problems, but getting 99 gear inches ain’t one.
Won’t be able to run a 50t chain ring unless the crank is a compact ie. BCD is 110mm
I use and recommend 50T
I’ve used a 48T with 6400 with no problems. Actually I’ve used a heap of different combos 8, 9 and 10 speed with 6400 and no trouble.
Sorry I lied. It is the inner ring where you are restricted… 38 teeth is the smallest.
The smaller difference between rings will actually improve shifting. I have a 48 big ring on one roadie and it’s great, live in the big ring most all of the time
48t big ring on the beardo supertourerer = big ring lyfe 
also allows use of the 11t sprocket
sheldon be refering to the ramps, pins, missing teeth etc on the chain rings which should be matching to get full benefit, front derailleurs worked fine before any of that crap was invented however