do you mean "curved" as in the type of chainstays that flare out at the rear hub to fit a large cassette, or curved as in flaring out near the bottom bracket to fit large tires? the former wouldn't make sense for a bike made for a single cog rear wheel, but the latter would make sense because Surly's always advertising their Fatties-Fit-Fine design. I personally always thought they were straight.
2012 redline conquest pro / 2008 yeti 575 / motobecan fantom cross uno
well, we think that somehow his chain threw and bound up around the BB shell and rear hub/chainstay area. we really don't know. it just happened while we were riding. one or two teeth on the chainring are all fcked, too.
there was no fall involved. we don't think the tooth could have been bent before, he would have been able to feel that. we had been riding for a good 3 or 4 miles before this happened.
please post your conspiracy theories.
The teeth could have been slightly bent before, not as noticeably, obviously. Maybe it happened at a bike rack, when someone else accidentally dropped his bike on your friend's or some BMX-er wasn't paying attention and smacked a beefy platform pedal into the chainring. However it happened, if it was slightly bent in the days or hours before the ride, maybe the repeated pressure of the chain on the teeth exacerbated the problem until they were bad enough that the teeth threw the chain like that. Maybe the less-than-perfect chainline of the Steamroller helped to apply pressure in unexpected directions that encouraged the damaged tooth the bend more, combined with 3/32" chain designed to be derailed.
This is all theorizing before my morning cup of coffee, so there are probably all kinds of holes in this explanation. It makes sense to me, though.