Originally Posted by
gauvins
Well, I am not experienced enough to be categorical here, but based on the data I looked at, sites like MMR average gradients to such an extent as to hide the most critical sections. (ex. one km at 8% with 200m at 25% will show as a section with a (benign) 10% gradient. On some sections, the terrain may be such that there are many many problematic sections. Although it may look like elevation gain is a critical metric, steep gradients are much more problematic.
We'd be two adults that there wouldn't be such fuss. But with kids...
hmmm.... are you aware of the tribulations of Vesta team? (a Volvo 65' that has participated in the previous Volvo ocean race). They hit a reef in "the middle of the ocean", east of Madagascar. Most likely their route had been planned at a small scale, so small that the tiny reef didn't show on their screen.
Incredible pictures. But the really mind boggling thing is the root cause of the accident. (see the official report
here). Quite incredible that no-one ran a large scale analysis. Quite incredible that large-scale analysis is not a mandatory feature of routing softwares.
So yes, it is great to have "the big picture" but if it is not fine grained enough, it can actually lead you to a false sense of security. (writing this, I realize that bike touring is unlikely to lead to dramatic situations -- please keep in mind that I am trying to figure what is a reasonable route for our tribe.)
FWIW -- I ran the data for the entire EV6-EV13-Istanbul route. Took a couple of hours (minutes for the actual charting -- more time was spent on locating GPS traces.) I would like to add that my understanding of the Sierra Cascades profile may have been caused by crummy routing. Will try to find the definitive tracks before we make a final decision on this.
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on a related note --
anyone knows how to calculate the maximum achievable gradient? I mean, a cyclist can deliver a finite amount of watts. So this figure has to be determined by gears and weight (air resistance not being crucial when you travel at 6kph 
(again, that will be useful to achieve a fair balance between our (low watt) pre-teen and (average watts and loaded) adults.
Hi there Gauvins,
Its interesting, but you sound like you are either an engineer or a computer software sort of guy--I don't need to know but I do have a computer friend who tends to look at stuff in a very analytical way like this. I'm not meaning to be critical, and in fact I have often thought of how it would be neat to have an idea of what wattage I put out comfortably, and to relate this to a given gradient along with the specific bike+load weight (I often think of this while biking up Mount Royal here in Montreal along the paved Camilien Houde road, and people go by me rather quickly, but on bikes that weigh the same as my single pannier sometimes.
So what I want to say is that there really isnt any proper method to calculate these sort of variables, but realistically all you can do its to ride up similar hills to what you expect to encounter with stuff on your bike, and see if your gearing is low enough and how it is for you at a given steepness.
One other thing is that in the places I have biked the most, North America, France, the gradients on regular roads are generally not much more than 12-15%, and while you might encounter the odd short steeper section, you can't really expect to have the exact info on all places--but you can get out there and start to get a more realistic feel for how a given hill for you.
The 30% one you mentioned in QC is always going to be pretty rare, and unless you bike in Latin America or in England, on regular roads its very uncommon to see gradients like this.
So I guess the one thing we can help you with here is to give recommendations for gearing, for a given load weight, and at least you can get some good ideas on that end, but really, you and the "gang" need to get out and regularly ride hills to get more prepared physically and psychologically. People who dont ride hills much often get psyched out by them, and while of course your gearing is a very important factor, a certain mindset is good to develop as well.
I like and use the old saying, that "there is always another hill", and to just concentrate on a bit at a time while going up a long hill. Also, its completely fair to realize that if you or your family dont ride up hills that much, at first it will be tough, but we do get stronger over time.
That said, getting some impressions on weight/gearing from some of us that are experienced, will go a long way for you to be at least reasonably sure that the gearing on your bikes are suitable for what you want to do.
again though, that said, nothing substitutes getting out there and riding hills. You will get stronger over time and you will become more mentally prepared for a hard climb. You will also develop a feeling for what you can get up, and if you need to lower your gearing, for example.
Do realize as well that sometimes, you or the kids may have to get off and walk up a short steep section, but thats ok and not the end of the world. I personally dont like pushing a bike, but over the decades have gotten a much better idea of what gearing works for me for a given sort of road.
I feel its unrealistic to look for some sort of "calculator" that can give you a black and white number, but getting out and riding certain types of hills will very much help you get stronger with them, and to know how much load is too much (weigh your panniers and or the bike in total) and to see about changing the gearing on your bike (although that is something a number of us can tell you right away if you give us the info, wheel and tire size, chainrings, cassettes....)
cheers