Part of the overwhelming appeal of the four-door Jeep JK is credited to a long wheelbase and a new, spacious interior. When compared to the earlier TJ or even the TJ Unlimited, the new JK lets you take more of your gear out for the ride. Unfortunately, more stuff inside means more weight. Add new bumpers, tire carrier, 35-inch spare tire and a couple of passengers and your JK suspension will be in for a treat at the first dip in the trail. A 5- or 6-inch lift will certainly increase compression travel, however a tall suspension wasn't desired or needed for this particular JK.
The search for a mild lift and tire combo led us straight to a new product offered by JKS Manufacturing, Inc. The ACOS name represents a new "Adjustable Coil Over Suspension" kit which is available for Jeep XJs, TJs and JKs.
The JKS kit offers easy ride height adjustments combined with the advantages of nitrogen charged bump stops found common in desert race truck suspensions.
The Bilstein bump stop shown here is common to Baja race vehicles. The JKS cylinder is designed on the same basis.
Starting with ride adjustment, we can appreciate the luxury of making easy adjustments at all four corners of our JK. As delivered from Chrysler, this particular JK sat low on the passenger side when the fuel tank was full. Aside from the gas tank factor, it is also fair to assume that our coil springs will eventually settle in one area more than another. These real world conditions are where the ACOS product really shines. Adjustments up to 2-1/4 inches can be made without removing suspension parts from the vehicle. A floor jack and socket head wrench are all it takes to regain an even ride height. We'll explore more details of the ACOS components in the installation photos.
The integrated nitrogen bump stops offer the second favorite feature of the JKS ACOS kit. The purpose of a gas charged bump stop is to provide 2-1/4 inches of controlled suspension compression before the axle tube reaches the frame mounted, static bump stop. Without the ACOS bump stops, we might be tempted to use stiffer coil springs to avoid bottoming the suspension. With the ACOS pistons in place, our JK has the ability to soak up the bumps affording a softer, more compliant set of springs.
Installation of the complete ACOS kit (front and back) can be done in one very long day or a more comfortable weekend. Minimal cutting on the rear and welding on the front is required but nothing of any substance. In the realm of Jeep building, nothing is permanent. If we choose to keep our ACOS components and sell the JK at a later date, going back to a stock configuration would be a fairly easy task.
We think the ACOS system is a perfect combo if you are looking for a stock ride and mild lift height. Under full compression, 35-inch tires will clear perfectly on every corner with the ACOS lift.