hey there Yan, one thing that I've been meaning to write but never got around to --- for those of us who have toured in far off places, we all know how we must always keep in mind a safety factor to avoid a dangerous situation somewhere where help would be sketchy or worse.
A few times I've made mistakes and gone too fast, and then realized that I had to be more careful and leave more safety margin--so lesson learned.
The one factor that helps with me being comfortable with X speeds for a given specific situation is that compared to my old touring bikes, the present one is so much more stable, handles really well even with a reasonably load on it (to avoid a pothole or whatever) and the mechanical disc brakes slow it down so, so much better and easier than my older bikes.
The last part about it braking so much better is the main factor, making descents so much safer for me, as I know I can safely and quickly bleed off speed with little effort or fanfare.
But if I have to carry more weight than usual, then I add in more safety margin, same with if the road is sketchy or whatever--but we all know and do this, so despite this back and forth about scientific stuff, we all have enough experience to adjust our riding to the specific environment (and that does include taking into account being in a remote area or even a non remote area but where any medical help is far, far off coming, and sketchy even if present)
Yes I agree completely. The bike makes a big difference. I can't use disc brakes unfortunately. Parts availability are still a problem in a lot of places. It's not just the disc brake anymore. The bike industry has made a lot of standard changes in the last few years that have made things very problematic. The new "gravel" trend is the bike companies realizing they're going to run out of middle aged white men to sell carbon road bikes to. So now they're applying the same bling bling n+1 philosophy to the touring and adventure riding segment, which has led to big changes. Nowadays essentially all of the high end bikes available are using thru-axle disc brake hubs.
For example the Co-motion Americano. High end US based builder, supposedly their heaviest duty expedition touring frame. $5000 bike. Thru-axle disc hubs, which automatically eliminates it for an actual world tour.
https://co-motion.com/collections/si...ucts/americano
These are simply not available in developing countries. There was a guy posting on the R*ddit bike touring sub a few months ago who got stuck in Georgia (the country) and had to get a replacement wheel mailed to him from western Europe. That's ten+ days of time lost, messing up your entire vacation schedule.
So no disc brakes, no hydraulics obviously, no electronic shifting, no weird wheel sizes like 650b or 29+, no proprietary frame standards in the bottom bracket or headset shells, no boost drop out spacing. Everything has to be absolutely generic standard from 15 years ago. I ride a custom frame. I am using a modern drivetrain, but I'm using bar end shifters so I can slap an 8 speed cassette on there and keep going.
For brakes I'm using some Shimano XT BR-M760 v-brakes. These were the pinnacle of Shimano v-brakes from 20 years ago, from the last year before Shimano high end mountain groups went all in on disc brakes. They are the last generation of the old parallelogram v-brake design. They don't squeal like the early versions, and they work extremely well. But end of the day they still can't match disc brakes.