During a ride in a limestone valley, I noticed my rear tube was poking through the tyre. The casing had worked itself away from the bead & the resulting butyl bubble was quite a concern, right up to the point it dramatically exploded. The tires in question were GEAX blades. I have fitted different tires now, but would be interested to know how common it is for the casing to fray so. Furthermore, the tyre was only two months old.