So, what actually caused this flat? - eviltoast

Last month, for the first time in thousands of KM, I got a flat tire.

It was fixed (replaced tube) and I’ve happily ridden another 400km since.

But I ride at nearly max pressure for the tires, because I assume this was caused by a pinch flat. At the time this flat happened, I was not running low pressure, but lower pressure than I am now (50psi vs 60psi, perhaps), and it happened on a very low speed ride on a smooth trail… no hard hits.

This was a new tube that I installed about 350km earlier, so maybe “user error.”

But can someone tell me what might have actually been the cause of that type of flat?