Carbon rims

Danstuff is about right on the comparative strength and (importantly) stiffness of carbon vs. alloy. When dinosaurs roamed the Earth I had a pair of Mavic GEL 280 rims weighing surprise, surprise, 280g which is comparable to a modern carbon rim. They had the strength and stiffness of extruded custard.

The GEL280--- far from a favorite rim (thin walls and hard anodization are not a good pair) --- can make good wheels but its easy to do them wrong. Back then you probably used Robergel 3 star spokes and had under and non-uniform tensioned wheels--- its difficult with the GEL280 to find the sweet spot in tension before the spokes pull through and the Robergel spokes were extremely non-uniform. Wheels made from the GEL280 can benefit greatly from today's spokes and techniques (tensiometers instead of feel or sound) .

To add insult to injury I can even imagine that you used the GEL280 on a road bicycle with 126mm rear.. they were afterall sold as road rims (and a 36 spoke GEL280 wheelset was not much worse than some of the low spoke count boutique wheels Mavic served up in the 1990s)....