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The Jeep Wrangler JK uses a fairly basic combination of control arms, brackets, and rods to form a reliable and very effective steering and suspension system for use on the road as well as off. Jeep Wrangler JKs are fairly simple vehicles to modify for off-road use and the upgrade options are almost endless. Even though this suspension system is pretty straightforward, there are a few items everyone should totally understand before they choose a lift kit or suspension components for their Jeep. Not all Jeep lift kits are created equal. Some may actually be incomplete. At Viper Motorsports in Weatherford Texas, it is our job to help our customers understand how the Jeep suspension works, and how altering the suspension effects ride and steering quality so that you can avoid common problems and end up with a reliable, trouble-free, lifted Jeep JK.

CONTROL ARMS
Control arms connect the axles to the frame. On a stock Jeep, there are 4 control arms for each axle: two passenger side (upper and lower) and two driver side (upper and lower). The control arms pivot at both of their mounting points (at the axle and frame). This allows the axle to articulate up and down while also preventing forward and backward movement. Lateral (side to side) movement is controlled by the track bar. The coil springs on a Jeep work in conjunction with the control arms to perform the same function as leaf spring does on a truck.

Since stock Jeep control arms are a fixed length, lifting a Jeep will cause the axles to move toward the center of the vehicle. Installing adjustable control arms will allow you to move them back outwards and also will allow you to correct the tilt (pinion angle) that the axle would have developed with stock (non-adjustable control arms. Adjustable control arms also allow you to adjust caster which helps your steering wheel return to center more easily after turning. If you lift your jeep (generally more than 3") without caster correction, the front caster angles may become more negative, creating "flighty" steering. Adjustable control arms are the most effective way to correct this problem. Most cheaper lift kits don't include adjustable control arms... that's one reason they are cheap. Any lift kit over 3.5" that doesn't include adjustable control arms is incomplete. Adjustable control arms correct pinion and caster angles as well as wheel base. Typically, adjustable control arms have higher quality joints for less bind and clearance for bigger tires. Longer, adjustable control arms will also keep the axle from trying to steer itself as the axle articulates (moves up and down).

"Do you need all 8 adjustable control arms?" If you lift your Jeep over 4", 8 adjustable control arms is a good idea. If you are on a budget, start with front lower control arms which are commonly used for adjusting caster (adjusted longer then stock). Front uppers can also be utilized (adjusted shorter then stock). Next, it is a good idea to add rear upper control arms for optimal pinion angle (especially with a 2 door with a shorter rear driveshaft)

ADJUSTABLE TRACK BARS
In a coil spring suspension, the track bars are the only thing keeping your axles from moving side to side. Keeping both axles centered properly is what keeps your Jeep tracking straight down the road. Since the track bar's job is to restrain the left and right movement, loose track bar bolts is the first thing you should check for if you have ever experienced death wobble (axle moving violently from left to right).

The factory Jeep track bars (front and rear) are non-adjustable. When you lift your JK (especially in excess of three inches), your suspension geometry changes. Increasing suspension height will force the axles to shift laterally (side to side). Since the factory track bar is too short to keep the axle centered, the front axle will move toward the driver's side and the rear axle to the passenger side.Adjustable track bars will allow you to re-center the axles and will also add some rigidity to the front suspension and the steering.

Some lift kit manufacturers will utilize a rear track bar bracket to maintain the factory position of the rear axle. Many cheaper lift kits don't provide adjustable track bars or brackets... that's why they are cheaper. At Viper Motorsports, we won't install a lift kit over 3 inches that doesn't include adjustable track bars.

DRIVE SHAFTS
Once you exceed 4 inches of suspension lift on your Jeep, you will need modified drive shafts to maintain proper universal joint angles. Although a modified drive shafts are almost never included with a suspension lift, damage to the factory drive shafts and differentials will eventually occur once the universal joints reach their maximum working angle.

STEERING GEOMETRY
If you drive your Jeep over a bump or into a pot hole and the steering wheel jerks to the left or right, you have just experienced "Bump Steer". Bump steer is a result of the track bar and drag ling angles being too steep. Basically, your steering geometry is off. If you are driving over a bump with one tire, the vehicle will try to steer itself. This usually becomes a problem at about 4" of lift height and the fix is the installation of a steering correction kit which flips the drag link and installs it on top of the knuckle on the passenger side instead of being connected to the bottom of the knuckle. Some cheaper lift kits accomplish steering correction utilizing a drop pitman arm. This is why they are cheap. At Viper Motorsports, we advise against installing a drop pitman arm as this is a short cut and is also BAD DESIGN. It puts too much stress on the steering box and will likely result in a very expensive problem in the future.

SHOCKS
The average Gross Vehicle Weight of a Jeep Wrangler Unlimited is 5500 lbs. The GVW of an average Chevrolet Silverado ranges from 6500 lbs to 7200 lbs and a Silverado 2500 ranges from 9300 lbs to 9900 lbs. Many lift kit manufacturers boast that they build lift kits for every type of vehicle. The problem is that they also utilize the same shock in different lengths for every application. This is why "cheap" Jeep lift kits often have ride quality comparable to a dump truck or a tank. Companies that build lift kits exclusively for Jeeps typically utilize shocks that take the weight of the Jeep into consideration. Some manufacturers will offer lift kits with no shocks so that you can buy a more suitable or adjustable shocks separately

Shock length is the axle's downward limiting factor. Adding height reduces downward travel if you continue to run the stock length shocks. A stock Jeep shock has around 8 inches of travel. Shock extensions are often included in cheaper lift kits and are an inexpensive way to add downward travel. While they do work, they limit upward travel if the jeeps suspension is set up to utilize all of the shock's travel. Most shocks list lift ranges in 2 inch increments example: 0-2",4-6" etc. but you'll want to choose what works best with your suspension setup.

LIFT HEIGHT
Most people will agree that any Jeep lift 2.5" or less will not necessarily require adjustable control arms or adjustable track bars etc. That being said, most aftermarket coil springs are designed to not sag under additional weight. Some note in the installation instructions that (listed heights are with a fully outfitted jeep). If you are not installing 3/8" steel bumpers, a winch, tire carrier, body armor etc, it's not uncommon for a 2.5" lift to give you 3.5" of lift height. When deciding what size lift to install, it is a good idea to consider your master plan for all of your additional parts and accessories.

TIRE PRESSURE
Once you decide to lift your Jeep and install those 35" or 37" tires, it is important to realize that most 35" and 37" or larger tires are 10ply tires intended to carry heavy loads. Jeeps are not heavy. If you follow the tire pressure information listed on the side of the tire, you will be in for a rough and flighty ride and some very uneven tread wear. The correct air pressure depends entirely on the actual weight that the tire is supporting. There are several ways to determine the proper air pressure for your Jeep. Most Jeep owners end up somewhere between 30 psi and 36 psi cold. If you are driving a late model Jeep, you may need some sort of programmer to tell the Tire Pressure Monitoring System to stop telling you that your tire pressure is too low.