In Superman #11 the cover reads:
Now I know covers have a tendency to be a little... misrepresentative of what is actually contained in the issue, but I've read the issue twice. There doesn't seem to be any secret about it.
I hate to break it to you, but the secret of the suit is:
This is an amazing upgrade for the Man of Steel. It only took him twenty six years before he could do the same thing Spider-Man did after the Secret Wars with his black costume.
Robot Chicken did enjoy themselves with this bit as well: What happens to Superman clothes while he's out "saving lives?"
I think the better explaintion should be that his superman clothes are of woven Kriptonian origin and therefore much more duriable than earth clothing and when Clark Kent changes into Superman he is moving so fast that the earth materials simply fall apart due to friction with the air.