On tirerack, the non-K1 285/30/20 has 0.7" more tread width, is that what you see? If the grooves on the K1 are also wider, but has the same pattern, does the K1 skip a column?
The narrower groove pattern but same tire width leads to the rounded sidewall you're talking about?
Try bouncing them up and down vertically on the ground or hit them with a large metal tool to feel if the rubber compound is any harder/softer..
For the same size tire, the non K1 gives a larger track for better grip, but would be a little less nimble.. probably suited for their indicated purposes
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