I have the same bike with the stock wheels. Trek told me the hub is 8/9 speed compatible only.
BTW, I have a bike with the 105 and love it! I was intrigued by your question so I contacted Trek once I read your post, hoping it would be easier to do than get new hubs or wheels. My 1.2 has a triple up front and it is awesome even with the Sora.
Kind regards,
Oshkosh
Last edited by OshkoshBiker; 07-21-16 at 06:56 PM.