The present invention comprises tire treads having sipes or other voids formed of non-curable inserts, as well as methods for forming sipes or other voids within a tread using non-curable inserts and apparatus for performing the same. Such methods include providing an uncured tread having a width and a thickness bounded by an outer side and a bottom side. Such methods further include providing a strip of non-curable material, the strip having a width and a length. Furthermore, such methods include inserting the strip of non-curable into the tread thickness from the tread outer side and to a predetermined depth within the tread thickness to form a void-forming insert within the tread thickness. Finally, these methods include curing the tread with the non-curable strip arranged within the tread thickness. The inserts may be folded, which may occur as the strips are inserted into the tread or prior to such insertion.