You can ride up to Boston Harbor, pick up the Chehalis-Western trail, take it 20-ish miles down to the end and then pick up the Tenino-Yelm trail which would give you another 14 miles going east, and then I guess back again. Usually I ride the roads next to those trails (Rich Road to Old 99 to 507) and then I make a loop going from Yelm up to Nisqually/Lacey and then back to Oly.