there is now a new modified disc been out for a while ,where the exciterring is made of stainless,so far it's been 100% and will outlast the disc
norb
August 2010
Take it to a DAF dealer for diagnosis. Probably will be the abs rings. if the truck is under 4 years old it will be covered by warranty (known fault). The bonus being the rings are attached to the the discs, so you get free new discs and free fitting !!
dee
March 2010
might be abs segments on discs, they tend to rust away so sensor can't sense locking wheel. also another cause could be excessive play in one or more wheel bearings!