You're worrying about nothing. I built my Di2 bike specifically to ride in the rain/winter.I'm getting a bike (used) with di2 and I am wondering how the electronics will fair up on a roof rack in a driving rain at highway speeds? Anyone ever have any issues with this? Should I wrap them before or am I worrying about nothing?
Good to know. I wondered about this as well.You're worrying about nothing. I built my Di2 bike specifically to ride in the rain/winter.
Ultegra Di2 Electronic Shifting - Ride Review, Video & Tech Report - Bikerumor
As for mud and water, the system is (for all practical purposes) waterproof. In fact, Shimano says they’ve completely submerged the Di2 system at 10m (~33 feet) and it still worked. Real world application: Riding in the rain won’t hurt it. Putting your bike on a roof rack and driving in the rain at 80mph won’t hurt it, either.