[goldgunner]

Larry - My 80SC had all of the hinges significantly worn - 'wallered out' at the oblong spring hole and indeed - the right hinge was broken.

Having disassembled and reassembled with new hinge halves, I'd have to guess that a combination of things causes the right side to fail / break first:

The way the long spring forces the hinge open is not a 'square' and perpendicular operation: there is a significant side force that is not a problem in the hinge operation when the hinge's spring hole and the bottom of the hinge halve are 'full form' (new); as the hinge spring hole becomes 'wallered out' and the bottom and sides of the hinge half become worn - after 25-30-35 years of wear, the side force presses the hinge further and further from 'square and perpendicular', creating - finally - an interference with the closing sun roof that snaps the hinge rather than closing/folding the hinge. The way the spring nests and functions - the twist of the spring - seems to me to have the 'side force' to the right (passenger) side of the car. Perhaps accumulated tolerance and wear create the largest amount of variance on that side, resulting in first failure.

Before I had the new hinge halves produced, I purchased a used 'good condition' hinge assembly from one of the yards - like dc auto - and found that the wear on the hinge halve's sides, bottom and spring hole were pretty darn significant. After all, the breaking yards are offering 20, 25, 30 year old items: it's just a matter of time until they break also.