The way in which the spokes were bent in relation to the tips and handle.

[In a tone that implies that it was really obvious and everyone could have seen that if they just bothered to look. Which, to him, it is. People just never use their brains properly (when he was a child, he tried to be like Matilda and levitate things just by using more of his mental capacity. It didn't work, but he figured that he would just have to use it for other means.]

And as I said, if you are more careful now you will not have to replace it.