This is the way I have my bicycle carrier mounted to the front of my bus. The original rack was intended to be a bumper mount, but I tought it needed to be a little more stabilized at the top. There are two blocks that anchor to the fresh air vent screw holes, each with a carriage bolt sticking out to the front of the bus. A cross piece attaches to those bolts and has hooks on the ends that are supposed to grab the uprights of the carrier. This part was never really finished of perfected and the hooks have saftey wire wrapped around them to keep everything steady. This configuration has traveled several thousand miles and proved very effective. Does it affect fuel milage? Who knows, I'm already driving a brick, can it get any worse?

The last two pictures aare a concept for this type of rack in front of a space tire. The mounts on the bumper will have to offset the rack to clear the tire. Coming out from behind the tire and over the top, a brace would secure the top of the carrier. Ideally, this design would have pivots at the bottom and a quick release at the top so the entire assembly would fold out of the way for access to the tire.