In order to run larger tires, upgrading the steering linkages is a good idea. A heavy-duty steering damper helps control unwanted steering inputs, such as the Fox Racing Shox steering damper here.
The stock fenders on the YJ do not offer much tire clearance. The fender extension along the rocker up to the door could be damaged in rough, rocky terrain.
Adding a high-quality battery, such as the Optima Yellow Top, improves reliability, especially when winching. The cold air intake adds a little power, which the stock YJ needs.
Our personal preference is a Jeep with an automatic transmission for both daily driving and off-road adventures. A big part of the reason for this is the quality and utility of modern auto transmissions. The 4-speed automatic found in newer JKs with the Pentastar engines (2012 and later) is a great transmission for wheeling. But for the YJ, it’s a toss-up. The automatics of that era are not very useful, but they are easier to drive off-road. The manual shift transmission may be a better way to go.
Engine choices are another story altogether. First, any carburetor-equipped engine will be problematic if you drive and wheel in both low- and high-altitude areas. Fuel injection works much better. The 4-cylinder-equipped YJ is okay for wheeling with the correct axle ratios for the tires, but the inline 6-cylinder is better. The best engine choice is the 4.0L inline-6 that appeared in the YJ beginning in 1991. The earlier 4.2L inline-6 is not as desirable. The 4.0L features 177 hp and 242 ft-lbs of torque, multiport fuel injection, and a high-flow cylinder head. Finding a 1991 or newer YJ with the 4.0L inline-6 is the optimum choice.
Another option is to swap the stock YJ engine with the 4.0L. The 4.0L inline-6 was offered in Cherokees and Comanches from 1987, in the Grand Cherokee beginning in 1993, and also in the Wrangler TJ from 1997 through 2006. There are many engine swap options to explore.
The rear door hinges are adequate for handling the weight of the stock tire and wheel. Larger tires will need more support.
The stock hood hold-downs weaken with age, allowing hood flutter on the highway and in gusty wind conditions. These latches need to be replaced.
The stock four banger in the base model YJ offers good reliability but lacks power. Gearing helps for off-road adventures.
The stock skid plates on the YJ are sheet metal. The skid plates offer some protection for moderate off-roading.
The Stock YJ uses a twin master cylinder with a power booster. Manual transmission versions use a hydraulic clutch.
CHAPTER 2
TIRES AND WHEELS
Tires play a critical role for off-road performance. Striking a compromise between good highway handling and traction in all four-wheeling conditions is tricky. Choosing tires has become trickier for stock YJ replacements, as the market has changed and the choices are limited in the smaller sizes. But if you go more extreme, there are many choices, such as the Nexen Roadian MTX mud-terrain tire mounted on Raceline Monster beadlock wheels.
In 1987, the Wrangler YJ was introduced with 29-inch-diameter tires. At that time, 31-inch-diameter tires were large. When the YJ Renegade went on sale, it used 30-inch-diameter tires. Today, with moderate lifts, 35-inch tires are common on YJ builds. To run even a 31-inch-diameter tire requires about a 2.5-inch lift. Going up to 33-inch tires takes a 4-inch lift, and 35-inch tires require a 5-inch-plus lift. Tire diameters up to 40 inches are possible but require more clearance. We will explore lifts in the suspension chapter.
Mud-terrain tires, such as the Falken WildPeak mud-terrain tire (left), are generally preferred for serious off-road Wranglers. They are especially good on soft surfaces where the large tread blocks and softer rubber compound increase grip. They also look more aggressive. All-terrain tires, such as the BFGoodrich All-Terrain T/A tire (middle), appeal to more casual off-road use due to better wear and a quieter ride on the highway. While the AT tire may have a harder rubber compound, the increased tread area due to a smaller void ratio allows most all-terrain tires to perform with the equivalent mud-terrain tire in most off-road conditions. The Mickey Thompson Baja ATZ P3 (right) all-terrain tire blurs the line between mud- and all-terrain tires. More of a hybrid, the ATZ P3 features large tread blocks, a smaller void ratio, numerous sipes in the tread blocks, and a rubber compound softer than a typical all-terrain tire but harder than a mud-terrain tire. Many tires companies have introduced this style of hybrid all-terrain tire. This new category is often called extreme all-terrain.
Stock Replacement Tires
The stock wheels and tires on the Wrangler YJ are very small by today’s standards. The 15-inch, 6.5-inch-wide wheels allow few off-road tire choices. The 16-inch-diameter wheels offer more choices, but a maximum width of 7 inches restricts the selection. The 7-inch-wide rim of the stock YJ can handle up to about a 30-inch-tall tire on the stock setup for light-duty off-road driving. An increase in tire diameter requires a lift and more suitable wheels for the application.
Off-Road Tires
Most Wrangler YJ owners either purchase a used modified rig or plan to modify the Wrangler for capable off-road experiences. Larger tires are the current norm; 33-inch-diameter tires are on the small end of the spectrum. To use 33-inch-tall tires requires at least a 4-inch lift, while a 35-inch tire will need more than 5 inches of lift. Many YJs run 37-inch tires, and more extreme builds use up to 40-inch tires. Both require extensive modifications, usually a stretched wheelbase and the use of coilover springs and shocks.
Tires are the most-common performance modification to Jeep Wranglers. All-terrain and mud-terrain tires offer more aggressive looks and much-improved performance when you wheel off-road. But there is a downside.
All- and mud-terrain tires use a softer rubber compound, even softer on the mud terrains. This accelerates tire wear and increases rolling resistance due to softer tread compounds, so fuel economy takes a hit. The more aggressive tread designs of all- and mud-terrain tires increases road noise. This is most notable on mud-terrain tires. The larger tread blocks on a mud tire also increase tire squirm on the highway, which reduces handling responsiveness.
To have a good selection of off-road tires requires an upgrade to a larger, wider wheel. Taller tires will require a suspension lift for clearance. This improves off-road performance drastically. And the more-aggressive look of the all-terrain and especially the mud-terrain tires are an integral element of the Jeep persona.
All-Terrain Versus Mud-Terrain Tires
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