I've decided to continue this thread since there is so much good info. And any thread that includes the word "definitive" in the title should be just that.

If the 11 speed road (10 spd 4700) actuation ratio is in fact 1.4, then the cable pull for Tiagra ST-4700 should equate to an average of 2.82mm. This means that a Tiagra ST-4700 can be used with an older 1.7 actuation RD to work with an 8 speed system spaced at 4.8mm. If this is correct, it is an upgrade over running ST-R2000/2400 Claris.

My questions have to do with the front derailleur. There are all sorts of posts that say you can't run road and mountain FD's due to differences in cable pull which I understand. And some that say you can fudge it, with a double, which also seems logical.

But I have never seen any actuation or shifter cable pull numbers for "index" shifters for a front derailleur. I have read that the front derailleur cable pull is greater with the newer 10/11 speed shifters.

Does anyone have these numbers?

As time goes on I will be moving on from my downtube shifters and going with Ergo or STI. I am running a 3x8 with XTR RD-M910 and FD-M900. The 10 spd Ergo's would be great, but my left thumb has enough arthritis that I will need to go with STI's. I would like to stick with the derailleur setup as it gives me a really wide range with Dura Ace performance.

But it would help if front derailleur shifter cable pull numbers existed to see if the longer Tiagra pull will work.

It is not life and death. I do have an FD-7703, and I could probably run an FD-4703 with my FC-6503 crank; provided it moves the chain enough to get to the outer ring. And there is always Claris.

Thanks in advance for any suggestions.

FWIW... I routinely break open cassettes and re-space them, run alternate routing, (when needed), and I'll do mix-n-match with freehub bodies so I don't mind doing an out of the box mod.

John