A drive arrangement for a mobile robot and particularly for an autonomous surface treating appliance comprises a drive housing 90 adapted to be mounted on a chassis of a mobile robot and includes a drive motor 100 operatively connected to a drive shaft 102 having a drive axis. The drive arrangement further comprises a linkage member or swing arm 92 rotatably mounted to the drive housing 90 about a pivot axis, a first wheel 94 carried by the drive shaft 102, a second wheel 96 carried by the linking member 92, and means 98 for transmitting drive from the first wheel 94 to the second wheel 96. The means 98 for transmitting the drive from the first wheel 94 to the second wheel 96 is preferably a flexible track or belt 98. The arrangement acts as suspension for the wheel 96 maintaining the wheel 96 in contact with the surface being cleaned.
