Cyclocross is one of the most intense forms of racing and the bikes are more than just road bikes with big tires. The frames are generally beefier than road frames and they have cantilever brake mounts to give more tire clearance with the brakes. Many times the large chainring will be a 48t instead of a 53t and in some cases there will only be one chainring up front. A cross course consists of mainly field and light trail riding with a short road section and a few sets of barriers that must be crossed. The races are run like criteriums and the season is through the worst part of the year making for muddy courses and inclimate weather. Between the conditions and the barriers and the fast pace a racer needs to be in top shape and have good bike handling skills to do well in cross racing.