Rivnuts from Homestead, PA on 9/18/2022 2:24:51 PM:
Its good to see those about to undertake the trip are doing the research to know the conditions and constraints along the trail. That knowledge minimizes surprises, allows better planning and results in a more enjoyable trip.
The detour at McMahon's Mill is virtually all on paved country roads with short sections between the towpath exits and roads that are passable dirt, grass or gravel. There are some rolling but rideable hills on the detour roads that I have ridden with a fully loaded bike. If you want to get a profile of the detour you can input the map of the detour provided on the NPS site into a route planning program like Ride With GPS and you'll get a quantitative view.
The most difficult parts of the detour are where you leave and return to the towpath itself. There are a few feet of embankment at each end that you'll likely have to push your bike up/down to proceed on.
Having done the preplanning before departure, you can, of course, get real-time feedback on the trail by speaking with oncoming riders.
Have a great trip.