I know that Dan has commented on having to carry a huge amount of water on desert trips.
<nods> Yes, it is common for me to carry 26.5 liters of just water on my Great Basin (
https://en.wikipedia.org/wiki/Great_Basin ) desert transits. 6.5l is carried on the bike plus two 10l bladders in my panniers or atop my rear rack. That is 26.5kg/58.4lbs plus container weight for what amounts to a 3-day supply. When it is hot, I drink 8.5l/day and need a bit more for cooking. Food weight is extra (I probably scrimp too much there) and I sometimes have to carry heavier items like a 3+ season down sleeping bag to handle the temperature drops between day and night. I typically tank up on water before I enter the desert and replenish my food stores when I leave it, so the balance changes but weight is reduced overall when I no longer need to carry so much water. The heaviest loads are carried only part of the time.
Expedition-class loads are relevant to a discussion on weight reduction because what is left after accounting for consumable supplies like water and food can and must be lightweight.
For example, my Nomad fully loaded and provisioned for extended solo self-supported desert touring can easily weigh 57kg/125lb all-up. The bike alone weighs 20kg/44lb, so if you take away the 26.5kg/58.4lb of water, then what's left is "only" 10.5kg/23lb for food, clothing, cooking gear, sleep system, tools and the bags to carry it all -- pretty light. I go almost exclusively with dried food, but that of course requires water. I lose about 450-500g/1-1.1lb of body weight/day. I can't reduce the weight of the Nomad very much because I need the sturdy frame to carry the weight and the accessories on it (i.e. dynamo hub and lighting/charging systems and full racks plus bottles/cages, pump and mudguards) are necessary for the the task.
With the bike weight pretty well fixed, I'm left to make reductions in my load. When I leave the desert, I return to carrying "only" 6.5l of water -- an immediate 20l/20kg/44lb reduction. That's substantial and very noticeable. My kit is already pretty light -- down sleeping bag and appropriate pad and silk liner, one-person tent, small stove -- but with an eye more toward sturdiness and reliability/longevity more than weight because I ride solo and self-supported in remote areas where a breakdown could be problematic. In the past, I've found some ultralight kit works great for awhile but ultimately does not last as long in my use as things made just a little bit sturdier -- call it lightweight rather than truly ultralight.
Any weight reduction helps make for a more pleasurable ride on any bike, but a given loss is a bigger proportion of a lighter bike and load. For example, 2kg shaved from a bike and load weighing 21kg is a 9.5% reduction -- pretty substantial and easily noticeable. On my fully loaded Nomad at 57kg, 2kg lost is only a 3.5% reduction -- hardly worthy of notice -- and the equivalent of 2l of water, less than a quarter of my typical day's consumption and gone in a quarter of my normal touring day.
In terms of bicycles, my Nomad weighs 20kg and most of my randonneur bikes weigh 15kg. My lightest bike weighs 12kg. A 1kg loss from each is 5%, 6.6% and 8.3%. I'd have to lose 1.66kg off the Nomad to equal the 8.3% lost to 1kg trimmed from my lightest bike.
If I am riding a more "normal" largely paved-road tour, then I might take one of my rando-touring bikes for an immediate reduction of 5kg/11lb in bike weight compared to the Nomad. I do feel the difference and I can cover either more distance in a day or with less effort as a result -- but can't carry the weight I need to with the Nomad or go the same places as easily or at all. My old 700C-wheeled expedition tourer handled much less well with an all-up weight of 49kg/109lb and the 32mm tires tended to sink into dry lake "shorelines". Horses for courses.
[Typed while Graham was making his similar reply, so there'll be some overlap. Oh, well.
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All the best,
Dan.
