Never knew bars could break like this

It’s not as unusual as you’d think.

I’ve never done it personally- but that’s one of the highest stress places on the bike. The immediate shear line at the joint of the stem and the bars creates almost a scissor effect. Slam it enough and it’s going to start fatiguing the metal. Once it’s gonna go it’ll likely follow the grain of the casting, which is why you see the spiral here. A bad batch of steel will definitely exacerbate this, but it could happen to anyone.

Is it caused by double butting or similar id thinning weight saving technique or just caused by the piece not being de stressed before welding during assembly/manufacturing processes?

Edit spelling 😂

I have the exact same break on my first pair of bars (6ish years ago). I’m pretty sure it’s caused by clamping your bars down too tight mixed with impact from bigger drops