DMGCO2 Cartridges vs. Hand Pump
For some reason, I was thinking about flat tires, and CO2 cartridges vs. pumps. The general wisdom seems to be that CO2 cartridges have the advantage of being smaller, lighter, and more convenient (they inflate the tire in just a few seconds).
I typically carry three cartridges on mountain bike rides, enough to inflate just two tires. Each full cartridge weighs 62g, plus my little Microflate nozzle, which I'm going to guess weighs 15g. That's 201g.
I just put my hand pump on the scale: 125g. So the pump is actually 76g lighter, never runs out of air. Which means it removes any reason not to help a stranded rider. And since we're talking about mountain biking, I'm already carrying a pack with spare tube, snacks, water, etc.
I'll still use the cartridges for road rides. I usually carry just two cartridges on the road, so there's no real weight savings, and a limitless source of air isn't nearly as important when you can just pull into a gas station.