Originally Posted By: Carbon
I think seeking lower rolling resistance is a reason to minus-size tires, and you think seeking lower rolling resistance is a reason to plus-size tires.
WRT bike tires however, the effects are pretty well-understood: wider tires of similar construction roll faster. This is one of the reasons that over the last couple of years, the biggest tire manufacturers have started making their fastest tires in wider widths.
Here's a pretty comprehensive list of low Crr bike tires:
link
You'll notice right away that some of fastest tires are quite narrow; however, since that was published, wider versions of those tires have become available. In every case, the new, wider versions roll faster. The list hasn't been updated in a while, however. My own test on the VF record show the 22mm @ .204 vs .224 for the 20mm. The Crono shoes a similar difference in the 22m.
However, you'll notice that there are several tires on that list that are the same tire, but different widths. In ALL cases, the wider one rolls faster. In some cases this is actually due to the construction not being equal (the tread width/casing width ratio is different); but in some cases, they ARE equal. The Michelins are good examples of that. And based on Crr, the wider ones always roll faster.
Of course, factoring in aerodynamics becomes the tricky part, so what's "fastest" depends on a lot of other variables--and making that determination isn't as simple as it seems.