I've had some 27" Kenda go squiggly from the casing weakening. Not entirely sure what happened, but it happened to both. Maybe a bad batch? Same thing actually happened to one of my 23c Paselas too. Maybe it's me? I've been running a Pasela and a Cheng Shin (the Kendas went squiggly at different times) on the bike with 27" and so far solid performance.