Thanks guys. The other question I had is that the bottom bracket doesn’t have a plastic shield - i.e. the plastic middle part that connects the two cups in a traditional shimano bottom bracket. this means the Di2 wires and junction b could potentially be directly touching resting against the crank axle and I wonder if that would be problematic with a spinning crank axle slowly wearing away the wires. Should I do something (and if so, what) to keep the wires from being able to touch the axle?
Wrap everything with several layers of electrical tape.
You would just buy the bearings for a GXP setup… big detail is the non-driveside bearing. I like the angular bearings from Wheels Manufacturing… link to their BB90 page, pick one item from each box (1-5) appropriately for your GXP and you’re good to go…
http://wheelsmfg.com/bottom-brackets/bb90-95/bb90-95-parts.html
Thanks guys. The other question I had is that the bottom bracket doesn’t have a plastic shield - i.e. the plastic middle part that connects the two cups in a traditional shimano bottom bracket. this means the Di2 wires and junction b could potentially be directly touching resting against the crank axle and I wonder if that would be problematic with a spinning crank axle slowly wearing away the wires. Should I do something (and if so, what) to keep the wires from being able to touch the axle?
You can pick up the spindle cover from a Trek dealer p/n 281823.