The bare threads that you can see on the belt are the nylon thread that is used in the manufacturing process of all of Dayco`s Timing Belts and is NOT a manufacturing defect and will NOT cause any failure. There are two ways of producing the sleeve for the timing belts one is by welding the ends together by using heat and the other is to stitch the ends together, Dayco adopt the stitching method as this is the strongest.
Depending on where the belt is stitched the nylon thread is more visible (mainly at the top of the tooth).
I trust this answers your question but please do not hesitate to contact me if you have any further queries.
Dayco Europe S.r.l
So its a feature, but I dont like the way it looks, never having one look like that before, so I'm going to change it, for purely cosmetic reasons...