About 7 years ago, a friend whom I was touring with had his steel Bike Friday develop a large crack at the chain stay just posterior to the bottom bracket. I noticed when I was riding behind him a significant wobble of the rear wheel so I assumed it was the rim. Nope, it was the cracked frame. We were near Little Rock, Arkansas and he found a welder who in fact welded it back together so he could continue the tour. It wasn't pretty but seemed to hold up well enough. What didn't hold up well was his rear wheel's hub which shortly thereafter became problematic and was then in need of replacement. The hubs on his Bike Friday were not standard dimensions and he had a helluva time finding a replacement. I think the crack developed, not because of an acute event but rather from him carrying so much damn weight on the rear for years. I loved touring with the fine fellow because he brought everything but the kitchen sink, though I did think I once saw a faucet sticking out of his rear pannier. Though I've toured with a lot people over the years, I don't think it's been a million (not yet anyway, but here's to hoping)