Surly 26"-29" CroMoly Rear Rack: BlackSurly 26" 29" CroMoly Rear Rack: Black. Surlys Rear Rack is made of tubular CroMoly steel and is designed for expedition touring. The Rear Rack is also height adjustable and can fit a wide selection of wheel sizes while allowing you to keep the center of gravity as low as possible for a stable ride. The stainless steel hardware we provide will enable you to fit them to most rigid 26 700c and some 29+ frames and forks equipped with drum caliper or