In reply to BigLob:
The estate track running up the W side of the glen past Glenfeshie Lodge fords the river at NN 852906, and the ford is usually OK with a bike in dry weather (snowmelt excepted, but I doubt that's a problem this far into the year). Using it would allow a short anticlockwise circular ride starting from Tolvah and getting back to the W bank via the bridge Welsh Kate mentioned. There's also an excellent longer circuit starting at the glider strip near Lagganlia and taking the W bank footpath at Feshiebridge.
You need to be aware of two get-off-and-walk bits on the E side: one about 1.5 km S of the bothy, and the other at the mouth of Allt Garbhlach about 2.5 km N of the bothy. The latter is avoidable by going about 200 m upstream.