Never worried much about rolling resistance when touring loaded. With the 40-50 pounds of stuff on the bike rolling resistance loses any importance.
Rolling resistance is a coefficient, not a constant, and the more weight you have on the tires, the harder is is to push them forward. IOW, weight has a direct effect on that effort needed to roll them. If you were on flat ground, the best racing tires' rolling resistance make it like you're climbing a 0.4% grade. Not caring what you get is likely to double or triple that, making you do
the equivalent of having to haul all that weight uphill more than you planned, by a grade of almost 1%. That's not steep, but it will have an effect on the number of miles you can do in a day.
That said however, what most people don't realize is that if all other factors were equal, the wider tire will actually have
less rolling resistance than the narrower one of the same model, even though the narrower one can handle more pressure. The reason is that the wider tire does not have to bend as sharply at the edge of the contact patch. There are several good web pages about this, one being
http://www.rouesartisanales.com/article-1503651.html .
Are beefier tires better for hauling weight?
I have not done touring heavily loaded, but if tandem use is any indication, a lot of road tandem teams use 23mm (skinny!) tires and it works out just fine for them, even though the gross rolling weight is at least 300 pounds. I never go that narrow on ours, but it shows it can be done.
Dont want the bike getting squirley when I hit the soft shoulder with all that weight?
For soft shoulders, yes, you'll need a tire wide enough to support you adequately in the soil (gravel, sand, etc.)
This message was edited by whittierider on 3-18-08 @ 11:14 AM
