Dead Bicycle Tire

After a ride to school and back with an annoying rhythmic sound and very minor damage to my bike, I identified a tumor of the sidewall of my real tire (always the rear one, the harder one to get on and off).  I feared the tire was failing and that I was going to have to replace it.

I was right.

This is the interior of the tire after I turned it inside out for inspection. I don't know what caused this but the damage is done and there is no repair that I know of.

New tires are on order but I suspect my riding to school won't resume before the end of the semester.