We weigh 305. Bike weighs 36 stripped. We have a Tubus Cosmo, a light rack bag, and the usual gear. 4 bottles. I'm guessing 50 lbs. or a little less, wet. We've pinch flatted once, on a sharp pavement edge.

In winter, we're running 25c Duranos at 115. In summer we run 25c Conti 4000s Black Chili, at 120 lbs.

The worst tire trouble we've had was a particular model of Conti blowing off the rim. Turned out to be my mistake - rim strip was a hair too wide for that rim/tire combination.

We've also run 23c TriComps at 140 lbs. They rode wonderfully and were very fast, but too fragile for tandem use: flats, sidewall cuts, etc. Just too much weight for the tire construction vs. road hazards.

We also run 28c Vittoria Rubino Pro Tech at 115 lbs. when we tour. I picked those because of the sidewall reinforcement. They work well, too, though the stronger sidewalls make them a hair slower. No biggie. I don't really care for the feel of them for sport riding. They change how the bike steers a hair. I don't know if that's from the width, the construction, or the width/rim width relationship. We run 36H Deep-V rims, about 19mm. Great rims for us. Tires stay on, easy to change with thumbs only.

I developed that calculation empirically, from what worked for us, guessing at the reason, but a good guess I think. Does make one nervous, though. We are not a heavy team and we are already running our tires at their limits. I guess heavier teams should probably tour with a Bob.