I used BFG's M/T's exclusively from 1986 until 2001 with one exception when I bought a set of A/T's - thought I'd see if I could get more than 18,000 out of a set of tires for a change. At the time they were the best available in radial OHV tires.
When the one (and only set, never again will I own a set of BFG A/T's or MT's for that matter - but that's a whole 'nuther story) set of BFG A/T's reached the same level of wear as yours have, I started to get some really weird blisters forming between the tread blocks. After the blisters opened we found the steel cords were poking up out of the tread. They say the tire carcass is the same as the M/T, but I never had the same problem with worn M/T's.
I tried to get them replaced, but the BFG rep refused to do so. They accused me of using the tires for desert racing, calling the damage high speed stone bruising. I had been driving over the typical lava mesa top trails found in central AZ. in my old 1970 GMC short bed. It's rough country, brutal on tires terrain no doubt, but certainly not done at racing speeds. On most of those trails you can't get above 5 MPH without beating the crap out'ta your rig and yourself.
Anyway, I'd not be willing to run the high country trails on those tires.
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I know a lot of guys replace tires at 50% wear, but frankly I can't afford a set of new shoes once a year. I average 14,000 annually, and usually get 2 years out of a set of tires on my daily driver. On my wife's truck the set of siped MT/R's have 24,000 on them - I expect to get well over 40,000 on them before they need replacement.
Traction wise I've not noticed an appreciable loss at below 50% with MT'R's in dry conditions. The compound is still soft enough to provide good grip. Obviously the traction suffers some in mud or snow at below 50%, but again, it's not that bad.