Wow educational stuff for sure. The 11-34 is an option too. It is a double up front if you mean two chain rings. The rder is what I was most concerned about. Although I never considered the possibility of it actually coming into contact with the cog. The current free wheel is a 13-26 and I think I can see a few worn teeth. BTW it looks to have ample space between the large cog and the hub. Spkt