Dave,
You need to be more descriptive. Where are the cracks? "Inside" is helpful, but are they near the bead, in the sidewall, radially across the tread/sidewall junction? All these indicate different things.
Plus, RunFlat tires fail pretty much the same way regular tires fail - and the symptoms are identical. The only exception I am aware of is that the stiff insert tends to mask sidewall fatigue. This occurs between the insert and the ply and it is completely un-observable until the tire is in the last stages of failure. This is why repairs to RunFlat tires aren't recommended.
