The Nitto Mud Grappler Extreme Terrain is an awesome off-road tire. We tested a set of 37x13.50R17 MGs on our Project TJ to great results.
If you intend to hit extreme trails, you'll need an extreme tire. Many exist that would be more than capable of meeting your needs, and some will perform in specific terrains better than others. However, a recent tire test landed us a set of tires that seemed to offer limitless possibilities in regard to capability in all terrains. Rocks -- no problem. Dirt, sand, and mud -- unstoppable. The Nitto Mud Grappler Extreme Terrain tire was well prepared for whatever we threw its way.
Mud Grapplers offer massive tread lugs and side lugs for attacking all types of terrain. The 15mm side lugs also create ample sidewall puncture resistance in addition to the enhanced off-road capability, and the tread lugs are siped for better wet traction, even in snow. A high void ratio between the lugs permits mud and dirt debris to be cleared quickly for continued performance, and enhanced lateral traction is achieved by means of anti-side-slip grooves. Two full-width steel belts line the perimeter of the tire, along with two spiral-wound nylon cap plies and a three-ply polyester high turn-up casing.
The Nitto Mud Grapplers are tough tires to say the least, and they worked exceptionally well for our off-road needs. Though not as favorable, our on-road experiences with these tires were also up to par. They do produce a fair amount of road noise, but this is completely excusable considering their off-road prowess. The steel belts are designed to offer durability and an acceptable wear life on- and off-road, but as with most large-lug tires, you'll discover most of the Mud Grappler's worth is demonstrated off the pavement.
TIRE SPECS
Tire: Nitto Mud Grappler Extreme Terrain
Size: LT37x13.50R17
Load Rating: E
Tread Depth: 1/32 in. (21 mm)
Overall Diameter (fully inflated): 37.05 in.
Overall Width: 14.27 in.
Max Load/Pressure: 4,300 lbs. at 65 psi
The sidewalls showed no signs of impending failure or abuse after we repeatedly hammered them through the trails in Moab. | 
Shown here inflated to just 8 psi, the Mud Grappler is rippled and beginning to fold over itself, but it's far from failure. The 8-psi to 10-psi range seemed to produce the most versatile and nimble effects, but we were also pleased with the tire's performance on the trail at higher pressures. | 
Measuring 13.50 inches wide, the Nitto MG provides a superb contact surface, even more so at a lower psi. The exceptional tread pattern offers multiple staggered biting edges, so the tire almost always has a biting edge attacking the obstacle at all times. |
The 37x13.50R17 Nitto Mud Grapplers are a good fit under our Project TJ. The tires were mounted to a set of 17x10 Allied Racing beadlock wheels. | 
Even in those instances when you're feeling a bit vertical, the Nittos will still grab. We had a winch line secured and pulling, but the tires were still a huge asset in conquering Upper Helldorado at Area BFE in Moab. | |