I have been asked to make this wedding cake, but as a car tire and not a bike tire. They would like it to be 12" round and chocolate cake. I will be traveling about 20 miles to the venue to deliver it.  I am really nervous about the best approach to take to support this cake standing up. I know I need to do stacked layers and carve it. (I am wondering if it needs to be changed to pound cake?) It doesn't seem like just cake boards in between the layers with just dowels will be enough support to keep it from leaning over. Has anyone attempted this or anything similar before that can offer me some experienced advice? Or advice even if you haven't attempted? lol  I would appreciate any opinions on any aspect of this cake! I am a nervous wreck about messing up someones wedding!