Packs normally include capacity by volume (cubic inches) and maximum carrying weight. Volume is pretty hard to fudge (though it can be done.) But it seems to me, having tried a number of packs this year in the search for a new one, that the maximum carrying weight rating is about as helpful as the temperature ratings on sleeping bags - they can tell you a lot about the packs within a given maker's line, but they rapidly lose usefulness when comparing packs from different makers.

What makes me think this is that my two finalists (both weighing 3 pounds and holding about 3600 cubic inches) claim carrying weights of 40 and 45 pounds, though I'll never carry more than 25. But, when I try the packs that are rated for 20 or 30 pounds, I can't find one that's comfortable.

Anybody have any thoughts on the reliability of these ratings?