There are two parts of the Muong Khu trekking route that are especially well suited to biking. One goes from Ho Chi Minh Road to Thuong Village, just outside of NSNL NR in Thanh Hoa province. The other goes from Ri Village to Mon Village, both of which are inside NSNL.
Please check the map at right for more detail; both biking routes are in yellow. There are local bikes there waiting for you, but if you desire a mountain bike you can bring yours. You will never forget the experience of cycling along these peaceful roads surrounded by impressive, forest covered mountains.