Mongoose Massif March 19, 2014March 7, 2016 RandyBicycle Gallery The Mongoose Massif fat-bike we got our Grand-son for his 12th birthday. The bike has 20″ x 4″ tires, 7 speeds and disc brakes. Purchase online… Him and I on his first ride on the bike. Me on the Mongoose Dolomite. Share this article: