I bet a low powder charge would bounce off the tire. Those things are pretty tough. I had a bb gun what shot at 600 fps and it bounces off regular car tires (they were used, dismounted tires). Its a lot smaller and weighs a lot less, but on a low powder charge a black powder bullet isn't going much faster and has a larger diameter. It also weights more so i don't know. Im willing to bet it bounces though.
There is no such thing as a stupid question, only stupid people.