What are my options for installing a FD compatible with Shimano Sora 3x9 STI brifters on a frame with top-pull cable routing? I'm thinking about converting a 1994 Trek 820 to drop bars. I already have the bars, brifters, rear wheel equipped with 9-speed cassette, etc. lying around, and I can get some compatible brakes, so as far as I see, my only issue is the front derailleur, because of the different pull ratios of road vs MTB shifters.
My question is, do you know of a top or dual-pull road triple FD? If not, what are my options? There's the Problem Solvers clamp pulley, but I can't find it in stock in any shop that delivers to Austria
Edit: Seat tube diameter is 31.8 mm.
There are no top-pull Shimano road front derailleurs. (Edit: This was wrong, they've made FD-CX70 in a top pull variant. It's contoured for cyclocross doubles and it's 10-speed. 10-speed FDs on 9-speed chains can be tricky or impossible to adjust to be free of rub, alhough manipulating the cage may solve that.)
A few different companies have made clamp-on pulleys like that. Origin8 is another one.
A lot of cross bikes have a pulley mounted to a braze-on. You can get the pulley part an from framebuilding suppliers, dead frames, etc. They usually use an M6 bolt. The question then arises would just doing it with an M6 rivnut be strong enough. I think it probably would be, but it would be an experiment.
If the downtube is a diameter you can find a clamp-on housing stop for, I think that's the good way. Put a housing stop there and a BB cable guide on. The hole for the cable guide is easy to drill and tap, and many shells have one there anyway.
The other clamp-on housing stop way is get a 31.8 one and clamp it on the seattube under the FD, then do continuous housing zip-tied to the downtube looped down and around the BB. This is easy to do, but the upwards-opening housing makes it the worst option because water contamination will foul it.
Remember to add an in-line barrel adjuster to any of these setups.