I have a trek 1400 road bike. I changed it to 3 chainrings. A bike shop added flat handlebar with deore xt sl-m 730 6 sped sis indexed - friction shifters. I found a pic online.. it said it could be 3 chainring compatible.. Sooo maybe there is a way to adjust the shifter to travel far enough. I have also had to add a new rear wheel. It has an 8 spd cluster( that ive adjusted to 7.i changed the shimano 105 rear derailleur to a suntour gt that had a longer touring cage.).the rear shifter works thru all 3 chainrings on my wind trainer with me riding it. So my limiting factor is the front derailleur shimano tiagra fd 4500 and/.or the shifter deore xt sl 730 adjustment or model. (These both came from a bike shop that i do not trust to go back to.. they also hyper cleaned my chain and rear cluster so they were beyond re greasing to any level of operation).

Cycling - Shimano