I tried a bump map to make treads with mixed results. First I had to remember that Pi was my friend. When I got an image that was 3.14 times the radius of the tire by the width I finally got a tread that didn't distort when applied. Next I had to get the zig and zag of the tread to meet back up at the ends so the tetxture could be seamless. I used the drawing thing in microsoft office. It has a nice snap to grid function. I could zig and zag between points of the grid and get the same spacing every time.

The tire was on an imported 3ds car with no mapping. I needed to apply the texture as a cylinder but the top of the tire was the top curve not the hub. I finally figured out by playing with rotating the x, y, z by 90 degrees that I could switch the top of the tire to the side of the tire and get the bump to map correctly. I think it was rotate Y 90 and leave the others zero but can't remember for sure.

I slapped everything together then decided to cut the wheels to steer for the road I had made. When I Turned the tires the bump stayed at 90 degrees. Here was no tread on the face of the tire and a little ghost tread floating in space where the bump should be if the tire were straight.

I played with rotating X to make the texture match the tire but gave up and finally discovered that if I used parametric texturing and rotated Y 90 the texture would track with the posing of the tire.

If you can get a mapped tire it's definately the way to go but it can be done without it.