Originally Posted by
WhyFi
Manufacturers are able to make such thin seat stays because they're not doing a lot of the heavy lifting. See Steven Kruijswijk's Cervelo: he crashed and then finished a TdF stage without noticing that he'd completely lost one of his seatstays -
Just riding around isn't going to stress that area enough to cause that kind of damage. An impact, like from a branch swept in to the wheel, is more likely to cause the type of damage seen on your 'stays. Knowing this explains why Spec "dragged their feet."
The same reason, if you look at a steel framed English bike, the stays are crazy, crazy thin. On a road bike, the front triangle and the chain stays bear all the load.
But failures do happen. For the old MTB folks, Titus as a company bit the dust when their Motolite replacement, the FTM, had a really bad habit of snapping seat stays.