So, this doesn't really seem to exist, and I had a couple spare minutes. With a sketch in CAD, I drew what is basically a 26" wheel, 27.5" and 29" hitting a square edge feature to put some numbers behind "rolling over rocks". A quick tangent about load transfer: the neck of the woods that I was involved in with racecars used the terms of "elastic" and "geometric" load transfer to describe the difference between loads that came from the tires and either went into the springs & dampers, or directly through the chassis. In the mtb world, this would be equivalent to pivot height in the rear suspension. A BB-concentric pivot location has poor square edge performance because a significant portion of the tire load goes directly into the frame (high geometric load transfer) and feels harsh, or "gets hung up". A super high pivot, conversely, has higher elastic load transfer, and much less of the tire load goes directly into the frame without first going through the spring & damper. Returning from the tangent, the below graphic shows the effective approach angle of different wheel sizes. With that, geometric vs elastic load transfer can be calculated. That will also vary directly with head angle and square edge height. I'll get to those calcs soon. Discuss.