Originally Posted by
Symox
What has led to stiffer rims - double wall construction, carbon, eyelets?
Shimano started laminating carbon onto very light aluminim rim sections quite a while ago, I think a C24 weighs like 365g... around the same time, milled ally rims were big (think Mavic Ksyrium etc), which allowed for more metal where it's needed without excess weight.
But mainly it's depth. Deep aluminium is super heavy, so you're talking carbon for that.