Thunder Bay mountain bike trail system being expanded A north-side mountain bike trail system is being expanded in the coming months, something Thunder Bay's Blacksheep Mountain Bike Club says is much needed due to the surging popularity of the sport. Social Sharing CBC News · Posted: Feb 25, 2021 8:30 AM ET | Last Updated: February 25 Mountain bikers ride the Trowbridge Falls trail network. The Blacksheep Mountain Bike Club is working with the City of Thunder Bay to expand the trail system. Work is expected to begin in May.(Brent Maranzan) A north-side mountain bike trail system is being expanded in the coming months, something riders say is much-needed given the surging popularity of the sport.