Rotate the result of a mirror modifier I am making a tire. The treads on the left and right side of the tire need to be offset from each other, ie, rotated about 10 degrees.
Is there a way to rotate the result of a mirror modifier? I tried using an array modifier with the array object being an "empty" that is scaled -100%, but the result is an inverted side.

Here is the half I have:


Here's the mirror result:


And here's how I want the mirrored portion to be rotated:


The way I produced this result was by applying my modifiers, but I need to be able to rotate the mirrored half without applying, if possible.

EDIT: I thought I was onto something when I realized that you can mirror using a  "mirror object", and the mirrored half will rotate when you rotate the mirror object, HOWEVER, it will only rotate in the other two axis: If I mirror over the X axis, I can only rotate the resulting half on the Z and Y axis. Seems like that should be an update to the feature.

EDIT 12-22-15: My workaround:

What I hoped to accomplish was to model an entire tire by simply only making the mesh for 1 tread on 1 half of the tire and using modifiers for the rest. That doesn't seem doable. For now at least, I modeled 2 treads, 1 on both sides of the tire, and will array that.
Ben, no the mirror modifier only produces symmetry across a plane; there is no way to rotate. One approach I used to model a tire was to model a strip across the entire width of the tire, and use an array modifier around an empty to arrange the instances of the array around the center point. The bit of the tread I modeled is outlined in white.

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I should note that I only modeled the raised parts of the tread, and not the side wall or base; these were a separate object.

This technique worked, but the results were unsatisfactory because I was modeling a real tire, and it turned out that the different strips around the tread did not have the same size; the left three parts of the thread occupied a smaller part of the radius (1/48th of the radius, as I recall) than the right two parts (1/40th of the radius), so what I wound up doing is modeling the tread pattern as two different bits, the three left in on bit, the two right in the other, and applying the two different segments around the body (the sidewalls, and base of the tread), as in the illustration, where I've rotated the tire body, and highlighted the two segment arrayed object for illustrative purposes.