Ridges under tyres

Chunky101 Posts: 108
edited February 2015 in Workshop
Checking my bike today before riding and noticed a couple of odd ridges under my rear tyre (Conti GT4000) They're about 10mm long and 2-3 mm wide. They aren't your typical inner tube bulge, it actually feels like there is something hard under there but unless the integrity of the tyre has failed I don't see how it can be as there is no opening. I threw caution to the wind and went out anyway and they were fine. I know the easiest option is to remove the tyre and inspect it but has anyone experienced this before?