Originally Posted by
fuzz2050
I'm fairly certain that isn't the case. A Camper Longflap, without the bagman, is 24 liters/ 920 grams, or 0.026 liters per gram. The Relevate bags (seat and frame) gets you 20 liters of carrying capacity for 650 grams, or .03 liters per gram.
+1 on the Carradice not being the lightest per volume. They are not even close. They do have some advantages though. For one the bag can be moved to pretty much any bike with little fuss.
BTW, a light-ish rack like the Axiom Streamliner (or lighter yet the Tubus Fly) with some light dry bags can come in lighter on a volume per gram comparison, depending on the volume you need. My Streamliner, eVac Dry Sacks, and all the attachment stuff weighs 710g and can adjust between <20 liters and 40 liters depending on how far you roll the closures down. This system came in cheaper that either a Carradice or Relevate bags.
Each system has it's own advantages and disadvantages. Which one works best depends on the tour and the rider's preferences.