Why do Daleks in Remembrance of the Daleks wobble?

Why do Daleks in Remembrance of the Daleks wobble?

The Daleks in Remembrance of the Daleks are known to wobble from side to side as they move during outdoor location scenes, but why is this? All footage and music is the property of the BBC. For more behind-the-scenes Dalek facts, check out Dalek 63•88: http://www.dalek6388.co.uk/