Trek advises against it, saying 160mm is max on the EXE. But, when I was in Canada recently, spoke with guys that had done just this. Running 170 on the front. They seem to have a positive experience. I have an extra Fox 36 and extra 170 air shaft so may try it soon.
I have seen plenty of people riding e bikes at Downieville. Most take the shuttle to the top. If you want to climb the fire road it starts off Highway 49 across from Union Flats campground. Its 10 miles 3700 feet of climbing. You would be best to call Greg at Downieville Outfitters and get...