I have a pair of Challenge Parigi-Robaix clinchers with only about 500 miles on them. The other day I swapped one onto a different rim for a special event, and tonight when I went to remount it back onto its original rim, I noticed this:



There is a noticeable groove about 4" long between the tread and the gumwall, which seems to expose the casing. I'm not sure if this is normal and just a cosmetic issue (I know these tires are thin thin thin, with fragile casings and basically a painted on gumwall), or if this is a sure sign of impending failure. The groove happens to fall right on a fold line; when I deflate the tire that groove is where the tire folds onto itself.

Thanks in advance.