Thanks for the words of wisdom, I was told my bike already had the cable guide so the wire should just push through, but I would guess it wouldn't hurt to use the PartTool IR cables. Yes I already have the 6800 gearset on the bike, but the appeal to me is the 6870 is smoother and you won't miss a shift. The friends of my who have the Di2 claim they never will go back to Mechanical shifter again.