Redline
I agree with you about the center lugs being shallow. Any idea why they designed the tire that way? I'm sure it does add stiffness, and once that center part gets worn to the point that those lugs aren't biting well, you'd probably be about ready to replace the tires anyway... Still, it seems like it would shorten the usable lifespan of the tire, even though I'd still guesstimate these M-55's would last 40k+ miles on almost any truck.
In favor of the M-55, everybody I've talked to that has used them, LOVES them and acts like they would never buy anything else... But they are not "tire connoisseurs" like some people.
Also, M-55's are not as grippy/grabby as the M/T, but they are a LOT more grippy than something like a BFG AT. Not a "mud terrain", but they do have more void than any AT type tire I've seen, with the possible exception of the Cooper ST... maybe... AND I think they would look really cool on a 20+/- year old truck, and I'm not too proud to admit that this has something to do with my desire to lean away from the Toyo M/T - I'm one of the oddballs that thinks Toyo M/T's are ugly as sin, even though they work really well.