Mountain biking is a popular activity in urban areas, including in forest remnants in Australia cities. To increase the technical challenge for riders, trail technical features such as jumps, bridges, mounds and ditches, along with informal trails are often constructed without authorisation. We assessed the social, environmental and management challenges associated with the presence of such features, developed a method for assessing them, and then used this method to examine them in an endangered forest within the Gold Coast in Australia. In a 29 ha remnant of Blackbutt (Eucalyptus pilularis) forest there were 116 unauthorised features, mostly jumps, ditches and mounds, which collectively resulted in an area of 1601 m2 of bare soil and 4010 m2 of undergrowth cleared. Features differed in their size, construction materials used, and their impacts on the environment. Although nearly two thirds had low to moderate safety, most were in moderate to good condition, had fall zones and optional routes for riders. Management options for land managers, in this case a publicly funded University, include (1) feature removal and site rehabilitation, (2) conversion to official features, (3) removal and provision of an alternative location for official features, or (4) maintain the status quo. There are social, financial and environmental benefits and limitations to each of these options highlighting that unauthorised trail technical features are a challenge for planners and managers that often have no easy solution.