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The latest mud-terrain tire offering from Maxxis is the Razr. Featuring a new tread compound and tread block design, the Razr is designed to improve on-road performance and reduce noise while retaining great off-road traction and durability in all types of terrain.
For those with stock or slightly modified Wrangler YJs, the Maxxis Bighorn MT-762 is offered in several 15- and 16-inch-diameter wheel sizes as small as 29 inches tall.
The very aggressive Maxxis Creepy Crawler offers a high level of off-road traction in slippery conditions and in the big rocks while being DOT legal for highway use.
The Pro Comp Xtreme MT2 is another mud-terrain tire available in a wide range of sizes to accommodate mild to extreme YJ builds.
The Falken Wildpeak M/T features a stiff sidewall construction. This tire needs to be aired down more to achieve the same tire contact spread as a softer sidewall tire. At the top, the tire pressure is 28 psi and in the middle the pressure is about 12 psi, which is about the lowest advisable for non-beadlock wheels. The lower the tire is aired down (to 6 psi), the more effectively the tire conforms to the rock. This series of photos was taken on a much heavier Jeep. A lighter YJ would need even lower tire pressures for good contact patch compliance.
Tire Pressures for Jeep Wrangler YJ Off-Road
There are four important reasons to air down tires. First is to increase traction by increasing tire contact patch area. A 285 70-17 10-ply tire with inflation pressures reduced from 50 psi to 7 psi will increase the tire contact patch by up to 220 percent.
Second, aired down tires improve ride comfort. There is a significant difference.
Third is to reduce the chance of a sidewall puncture. Think of a highly inflated balloon. If you poke at it, it will likely puncture. A softly inflated balloon, when poked, has considerably more give and is not likely to puncture.
Fourth, aired down tires reduce damage to the road surface by spreading the weight over a greater tire contact patch surface area. This helps reduce erosion over time.
There are also some disadvantages, including reduced ground clearance due to a shorter sidewall from less pressure, increased possibility of the tire bead unseating from the wheel rim, and the need to air back to recommended highway tire pressures for your vehicle. For hard surfaces and rock crawling, higher pressures are needed to help keep the tire bead seated on the wheel rim and to protect the sidewall and tire bead from bottoming on the rim, which would likely damage the tire or even bend the wheel rim.
Airing down tires to a lower pressure allows the tire to conform to the terrain, increasing traction. This is very important for rock crawling for both climbing and descending. This tire is at about 15 psi and the tire contact patch and the sidewalls conform to the rock edge, allowing a much easier climb up the rock. With this Raceline Monster beadlock wheel, we have aired down as low as 4 psi on soft surfaces such as sand and snow.
Tire Deflator Types
Tire deflators are the easiest way to air down tires when you hit the trails. In general, there are three types of deflators.
The first type are tire pressure gauges that have a release valve for letting air out of a tire. These are very slow and require constant attention.
The second type are deflators that screw onto the valve stem and depress the spring-loaded valve core. These are adjustable for minimum pressure when they shut off. They usually come in sets of two or four. They are not much faster than a pressure gauge, but with four and automatic shut off, you can screw them on and walk away.
Wheelspin is always an issue when climbing steep rock ledges. The BFGoodrich Mud-Terrain T/A KM2 features a fairly stiff sidewall construction. Combined with the light weight of the YJ, this tire could have benefited from a lower tire pressure when airing down. The reduction in ground clearance from a lower tire pressure is not an issue, at least in this spot.
The Currie deflator removes the valve core from the valve stem, which allows rapid deflation. The gauge allows precise pressure monitoring. The deflator consists of a gauge, a plunger that unscrews the valve core, a fitting that screws onto the valve stem, and a pressure release valve. While the operator is a little more involved in the process, this is the fastest way to air down four tires—even faster than the set of four screw-on deflators. The cost is about half.
The valve core is spring loaded, so when the valve is depressed, air can flow in under pressure or out to air down. The airflow is very restricted by the valve core. The Currie deflator removes the core but captures it within the housing for easy replacement.
To use the Currie deflator, screw the fitting onto the valve stem, depress the plunger and rotate until it captures the valve core, unscrew the valve core, and pull the plunger out. Open the air valve to deflate, close the air valve to check pressure. When the desired pressure is reached, keep the valve closed, push in the plunger, and screw in the valve core until snug. Then, pull the plunger out so that the valve core cannot be unscrewed while unscrewing the fitting from the valve stem. Our project YJ weighs in at about 4,000 pounds. To get good tire contact patch spread on the fairly soft sidewall Nexen Roadian MTX tires, we aired down to about 6 psi. Beadlocks are a necessity at these low tire pressures.
This is a Mil-Spec Multi Choice Deflator from Extreme Outback Products. This high-quality deflator features detents from 20 psi down to 10 psi in 2-psi increments. It adjusts by rotating the knob on the top.
The Staun Tyre Deflators allow all four tires to be aired down at once. They are made from brass and have an adjustable pressure relief valve. They screw onto the valve stem.
The third type of deflator also screws onto the valve stem, but it also unscrews the valve core from the stem while capturing it within the nozzle. This type has a pressure gauge and on-off pressure relief valve for accurate control of tire pressure. This allows for very rapid airing down. One of these deflators is typically faster than four of the others. The downside is the need to watch the pressure as it drops.
Rock Smasher Engineering has a hybrid system called 2Way Air that uses a system of tubes plumbed into the vehicle. The tubes run to Schrader valves at each corner and to a shut-off valve. There is also a pressure relief valve that is adjustable
