Why is a 26" rim 25% stronger than a 27" rim?
I appreciate the physics of why a smaller diameter will have more rigidity but 25%???
Shorter spoke length and stouter(in many cases) rims make for a stronger wheel, all other things being equal. Also, mountain bike hubs seem more durable, and often have a higher or equal to 700c spoke count. Now, I'm not sure about 25% myself, but my experience is that I have had no broken spokes on tour while using 26", but I don't put the miles in anymore, either, still it is interesting to note that I have broken about 5 700c spokes this year in light touring(less than 30 lbs weight of load in terms of panniers). I might also add that on the 26" tourer, I have several times brought home a weeks groceries across mixed terrain, but only a distance of about 5 miles, over trail, road, part of a park and the sixth green on a golf course, and open ground across a field, then a paved trail and my street to home. (approx. 50 pounds)((weight and expense))