Yokohama Super Diggers-ever have 'em?

I'm looking at a set of used Super Diggers. They're at least a few years old, with a tread pattern that to me is not quite a mud tire, but more aggressive than an all terrain.The out side sidewall has several thick rings where the tread ends.
They're in good enough shape with decent tread left, however I'm hesitant about the composition of the rubber itself. It seems on the hard side, like it's made for high mileage, or maybe it's from age?
Has any of you ever owned these, or do you know about different rubber compounds?

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Bill Collins
93 Ranger XLT 4X4
Modified

 

[rockylaurence]

Be careful! You have to ask yourself--Self, why haven't these tires been run? Could they be out-of-round, Rough ride, hard to balance? The tires remind me of a Dirt bike knoby--they're tough! I've never had them but what I've read is good.