Using a Sora STI triple shifter on a double crank

[rice rocket]

Everywhere I see Sora 3400's listed as double/triple compatible. But when I read through the tech docs, it says the number shifts is dependent on the derailleur you use. I'm assuming the FD upper cable stop is what prevents you from shifting into a phantom 3rd chainring? Or is it some switch I flip somewhere that locks out the 3rd shift?

[CNY rider]

The high-low adjustment screws are what limits the travel and keeps you off the imaginary third ring.

[goonster]

I'm assuming the FD upper cable stop is what prevents you from shifting into a phantom 3rd chainring?
What CNY said: the limit screws of the FD limit the cable travel.

I installed this setup on a bike for the missus, and it works.

[Bob Loblaw]

The shifter will work. You will need a double-specific derailer, however.

BL

[eddief]

if you are using it on a double crank. the triple front d is dumb and if you set the limit screw so it thinks it is a double, it will act that way. be careful as probably less than half the stuff you read on the internet is true.