Hidden Valley Nature Center volunteer Shawn Day leads fat bike riders, bikes with fat tires, along the trails in Jefferson on Sunday, Nov. 8. Carl D. Walsh/Staff Photographer

Eoin O’Mahoney, 11 of Whitefield, relaxes after a fat bike ride at Hidden Valley Nature Center in Jefferson on Sunday, Nov. 8. Carl D. Walsh/Staff Photographer

A rider does a wheelie on a fat bike, a bicycle with fat tires, before a group ride at Hidden Valley Nature Center in Jefferson on Sunday, Nov. 8. Carl D. Walsh/Staff Photographer

Eoin O’Mahoney, 11 of Whitefield, rides a fat bike ride at Hidden Valley Nature Center in Jefferson on Sunday, Nov. 8. Carl D. Walsh/Staff Photographer

Hidden Valley Nature Center volunteer Sean Day leads fat bike riders, bikes with fat tires, along the trails in Jefferson on Sunday, Nov. 8. Carl D. Walsh/Staff Photographer

Hidden Valley Nature Center volunteer Sean Day leads fat bike riders, (bikes with fat tires), including Jon Arsenault of Phippsburg, along the trails in Jefferson on Sunday, Nov. 8. Carl D. Walsh/Staff Photographer

A biker rides a fat bike, designed by Carver Bikes of Bath Bike and Ski, called the Omega Beast, at Hidden Valley Nature Center in Jefferson on Sunday, November 8, 2015. Carl D. Walsh/Staff Photographer

Forrest Carver, of Bath, Bike and Ski, lifts one of the fat bikes the company designs, for riders to demo at Hidden Valley Nature Center in Jefferson on Sunday, Nov. 8. Carl D. Walsh/Staff Photographer