La Dérailloss is a low-cost mountain bike ride based in Fontaine-le-Bourg, Seine-Maritime, France, with check-in from 7:30 AM and starts from 8:00 AM. Les Déraillés 76 organizes it in April, with the format centered on several VTT routes instead of a single race distance. Riders select short, middle, or long options, with recent courses varying from around 20 km to about 70 km, and climbing from a few hundred metres to over 1,300 metres on the longest route. A non-timed walking or trail option of 12 to 15 km is also available, allowing participation for those not seeking a full mountain bike effort.
The VTT courses increase in difficulty: the shortest route has one refreshment stop at the finish, the middle routes include stops on the course, and the longest route may have three stops before the final one. The routes are listed with ONF validation, indicating forest sections are planned through the Office National des Forêts process. The event is local and club-run, with public VTT entry around 6 euros and a slightly lower club price, resembling a French rando VTT more than a commercial race festival. La Dérailloss offers a range of choices: a casual walker, a steady mountain biker, and someone seeking a challenging 1,000m-plus climbing day can all begin from the same village hall in Fontaine-le-Bourg.