O ciclista cai em um quadrado adjacente
Do DMG e do Compêndio de Regras [ddi]
Falling Prone: If the mount falls prone, the rider is dismounted and falls prone in an unoccupied space of the rider’s choice adjacent to the now-prone mount. However, if the mount is flying when it is knocked prone, it instead falls. The rider isn’t dismounted unless the mount lands and falls prone itself. A rider who is knocked prone can immediately make a saving throw. On a roll of 9 or lower, the rider is dismounted and falls prone in an unoccupied space of the rider’s choice adjacent to the mount. On a roll of 10 or higher, the rider is neither dismounted nor knocked prone. A rider who voluntarily drops prone falls prone in an unoccupied space of the rider’s choice adjacent to the mount.