Of all of the modifications I planned to make to my Jeep, the single most important and most difficult choice was which suspension system would be right for me. One of the Jeep's biggest assets - its huge aftermarket support - can make it difficult to narrow down which combination of parts is best suited to any one particular owner's needs. As I mentioned in my very first blog post, my Jeep's duty is as a daily driver, a comfortable road-tripper, and a capable 4 wheeler. The challenge I faced was overcoming the fact that trail prowess and street performance are generally inversely proportional.
It was my intent to combine the best parts from across the aftermarket to build what I consider to be the perfect Jeep. My definition of "perfect" is based on versatility. My goal was to build a Rubicon Trail-capable Jeep with better-than-stock ride and handling on-road. Working within a modest budget, was this even going to be possible?
Suspension kits for the Jeep are not created equal. Budget kits create ride and handling shortcomings because they focus only on raising the ride height without correcting the suspension and steering geometry, while high-end kits often include expensive, superfluous components that are either overkill or simply not even needed. I have plenty of experience building countless 4x4s over the course of my life and career and made my share of mistakes, but I wanted to build my Jeep right the first time.
If all I wanted to do was fit some taller tires, I could get by with nothing more than coil spacers and shock extensions. This doesn't fit my needs though, because it does nothing to increase the suspension's performance off-road and it leaves out critical geometry-correcting components to address the on-road ride and handling compromises. This might be adequate for a mallcrawler on a very slim budget, but I am unwilling to make compromises with my Jeep.
Once I determined what size tire and what type of tire I wanted for my Jeep, it was time to determine the amount of suspension lift I would need. The Wrangler's generous fender openings provide clearance for 35's with only 2 inches of lift. I found this minimal lift height quite appealing because it maximizes the Jeep's on-road handling, but I didn't want to sacrifice suspension up-travel and chassis clearance on the trails. Conversely, I liked the idea of gaining additional belly clearance on my long-wheelbase 4-door Wrangler Unlimited with a tall suspension lift in the 4- to 5-inch range, but I didn't want to raise the center-of-gravity and compound the issues with the suspension, steering, and driveline geometry that result from excessive lift. I also determined that my house's garage door clearance would allow my Jeep to be no taller than 4" suspension and 35" tires. This meant that a suspension kit in the 3- to 4-inch lift range was my target.
If I was building a dedicated rock buggy or high-speed desert prerunner, there are countless high-dollar kits available to choose from. However, I couldn't let marketing hype persuade me to dump big bucks into long-arm kits and remote-reservoir triple-bypass coilovers that would do little to help my Jeep's real-world performance. The JK comes with long enough control arms to not suffer from the issues that the TJ, XJ, ZJ, WJ, and MJ do with their short arms, so a long-arm kit is completely unnecessary for my needs. High-dollar coilover shocks are terrific for extended high-speed desert running, but absolutely unneeded for street, backroad, and rockcrawling duties.
I determined that I was shopping in the middle of the suspension spectrum, with an emphasis on geometry correction and spring and shock tuning.
I considered suspension kits from all the top manufacturers: Synergy, Teraflex, Offroad Evolution, Rock Krawler, TrailMaster, Pro Comp, Rubicon Express and Rancho. After months of homework, I finally narrowed down my choices to the following three:
MetalCloak's 3.5" Game Changer suspension was almost the winner because of its incredible suspension travel, street-worthy ride and handling, and well-engineered control arms and DuroFlex joints. I also appreciate the fact that it's American-made. However, I felt that this kit was probably more suspension than I needed for my Jeep's intended uses, not to mentioned priced out of my league. I wanted to be able to go to a highsteer setup with a flipped drag link and Reid Racing steering knuckles, but this suspension's incredible uptravel would cause steering interference with the Jeep's frame rail. Additionally, I wanted to able able to keep my drag link and track bars parallel to the ground and as high as possible to raise the suspension's roll center to further improve on-road handling, so I determined this system wasn't my best choice. Since making my final decision, MetalCloak has now released a more affordable system that combines their springs and other components with Old Man Emu's shocks. With less suspension uptravel, the highsteer I wanted to be able to use would work perfectly with this kit.
ARB's Old Man Emu suspension suits my needs very closely. OME notoriously provides a terrific on- and off-road ride because their Australian engineers design their suspension systems for long-distance overlanding across the Outback where rough, washboarded roads are the norm. I have firsthand experience with OME's springs and shocks on several of my previous 4x4s and can attest to the superior ride they deliver compared to comparable systems. Two of this kit's shortcomings are that it uses offset washers as a band-aid to correct the front axle's caster, and it offers no steering geometry correction so the drag link and track bar will cause the axle to move in a side-to-side motion as the suspension cycles up-and-down. Both of these issues can be corrected with additional aftermarket parts, but I determined another kit to suit my needs even more perfectly.
These two additions are certainly necessary upgrades when lifting a Jeep and installing oversize tires, but I planned to install even higher-end parts for these two features: a Superchips Flashpaq instead of the ProCal, and a highsteer kit with Synergy's drag link flip kit and an upgrade to Reid Racing's JK steering knuckles with Synergy's chromoly tie rod. More on those upgrades later.
There are a number of features that distinguish the AEV suspension from the rest. AEV sums it up:
There are a lot of suspensions available, what sets yours apart from all the others?
In simple terms: OE-style tuning. With the benefit of a former Chrysler suspension engineer on staff, we began by optimizing all of the JK’s control-arm, track-arm and steering geometry to accommodate a lifted ride height. We then proceeded to develop custom coil springs and custom-tuned shocks. All of this development followed factory engineering methodology. The overall goal was to not only build a lift, but to create a fully tuned suspension that would enable a lifted JK to outperform a stock one in all driving environments. We think we succeeded as AEV-equipped JKs not only have more wheel travel than stock ones, but can out corner them as well – and all without compromise to safety, practicality or comfort
Although the entire system is greater than the sum of its individual parts, each component stands out from the rest on its own:
Springs: AEV's springs are both progressive and frequency-tuned. In other words, they get stiffer to support heavier loads as weight is increased to fight suspension sag when loaded down with a weekend's camping gear, and their rates are tuned to the Jeep's specific oscillation frequency which allows the suspension to naturally settle itself after a bump in the road. Offloading this task from the shock absorbers allows the shocks to be better-tuned for their primary purpose.
Control arm relocation brackets: These are one of the key components that makes AEV's suspension ride and handle better than any other on the road. You can read more details of these brackets on AEV's website but to summarize it, the brackets reduce the control arms' angles for better ride quality and they adjust the suspension geometry to increase caster, reduce dive and squat, and minimize front driveshaft travel as the suspension cycles. I really didn't want to have to deal with front driveshaft clearance issues and the expense of replacing it with an aftermarket unit. Every negative trait of traditional Jeep suspension kits has been reengineered into a positive behavior with AEV's suspension.
Rear track bar bracket: Much taller than any other track bar bracket on the market, AEV's track bar bracket raises the vehicle's roll center as high as possible to promote flat cornering, increases stability when the Jeep is off-camber on the trails, and eliminates the typical "tail-wagging" sensation from the rear of the Jeep when large up-and-down suspension motions are converted into yaw movements. The raised bracket includes a forged replacement track bar that's shaped to clear the frame and exhaust.
At first I was apprehensive about re-using the Jeep's original control arms since most of the top suspension manufacturers supply new control arms with their kits, but after researching the available options, I realized that for most uses, the original control arms are all I need, and in most cases they are actually superior to aftermarket replacements (MetalCloak's control arms are excluded from this generalization). Both AEV and Old Man Emu understand the benefits to retaining the factory control arms. First, aftermarket replacement control arms are known for squeaking because of their inferior bushings; even Full-Traction Suspension's much-hyped Silent Ride System is notorious for squeaking. Second, poor control arm geometry further increases the propensity for squeaky bushings. To help us understand the extent of control arm geometry variation, MetalCloak created the following diagram that illustrates the superior geometry of their and the OEM Jeep control arms compared to a variety of aftermarket alternatives:
With all of these individual components working together, a Jeep lifted with AEV's suspension system outperforms any other suspension setup in nearly every terrain. Expedition Portal's blog points to a great video that demonstrates the AEV DualSport suspension's capability on road and track. This is not the sort of performance that Jeeps are typically capable of when fitted with a suspension lift, but AEV's superior geometry provides a clear difference:
Installing this suspension is incredibly easy. I was able to install mine in my own garage in one day, with nothing more than a normal set of hand tools. As mentioned earlier, I also installed some additional steering components that added to the total time to completion, but if you can follow AEV's thorough instructions and have a safe place to work, there's no reason why you should have to hire a shop to install this kit. Truly the only challenging part of the installation was accessing the upper shock mounts for the front shocks to remove the old ones and install the new ones. Bending and relocating the brake lines was a bit fiddly, but nothing that should be too difficult.
Some highlights from the installation:
|Before the installation|
|AEV 3.5" DualSport ST suspension components|
|Yes, you can install this kit yourself! Begin with the Jeep's frame supported by jackstands|
|Brake hose drop brackets are included for the front and the rear|
|One of the key components is the ultra-tall rear track bar bracket|
|Front suspension assembled; new steering components discussed in another post|
|Installation complete, shown before aftermarket bumpers and other accessories were installed|
As a baseline measurement, my 2010 Wrangler Rubicon Unlimited on the original 255/75R17 BFGoodrich Mud Terrain tires, original bumpers, and a hardtop measured 36 inches tall at the front fenders and 37 inches high at the rear fenders:
After installing the AEV suspension, Warn Stubby Rockcrawler front bumper, Warn M8000-S winch, and MetalCloak rear bumper and tire carrier, I drove the Jeep for several months and fully cycled the suspension on numerous off-road trips to ensure that the springs were fully settled to their final height before taking measurements at the fenders with the new 315/70R17 Treadwright Guard Dog tires:
The fenders now measure 41.5 inches tall front and rear, so by subtracting the 1.5 inch difference in the tires' radius, the actual amount of suspension lift equates to 4.0 inches in front and 3.0 inches at the rear - exactly what American Expedition Vehicles promised. Accurate lift height estimates were critical in my case, because I calculated that my Jeep's hardtop would only have 0.75" clearance under my garage door opening with a 3.5" lift and 35" tires
Ride quality from the suspension is terrific, especially if you've ridden in other lifted vehicles. The ride can best be described as smooth, but firm; it is similar to the factory tuning, but with much less "pogo-ing" over large bumps and frost heaves that significantly cycle the suspension. The control arm drop brackets smooth the impact from small, sharp bumps, but the firmer shocks dampen the body motions that come from a higher center of gravity. In my opinion, not only does the AEV suspension provide a better ride than other JK suspensions, it also rides better than a stock Wrangler with factory suspension. The only real negative to the handling seems to come as a result of the heavy solid axles and 35" tires shuddering over medium-size bumps at high speed (such as a parking lot speed bump at 25mph) when the tires are inflated to street pressure; when aired down to trail pressure, the tires absorb enough of the terrain that this
The flat cornering and nearly nonexistent brake dive result in unbelievable stability at high speeds. This is not an exaggeration. Simply put, you would not believe a lifted Jeep could handle this well - especially if you're accustomed to an earlier TJ or YJ Wrangler.
Where this suspension really shines is at moderate speeds on rough, unpaved roads. This was particularly evident to me during a recent trip across the Nevada desert, where I burned through nearly an entire tank of gas without setting a tire on asphalt. We covered a wide range of terrain from low-range rockcrawling to full-throttle assaults on rocky, washboarded backroads. A solid-axle Rubicon is no Ford Raptor, but the AEV suspension provides as much capability as the engine can deal out; on rough terrain like this with the tires at 20psi, speed tops out at 75mph in 4th gear (6-speed manual) while the tires and suspension absorb everything. The tires left the ground on a couple of occasions, but I slowed to reasonable speeds through unexpected washes and not once did the Jeep crash off its bumpstops.
Despite what some Internet forum detractors might insist, AEV's decision to use Jeep's factory control arms does not artificially limit articulation while rockcrawling. Of course high-deflection bushings in aftermarket control arms allow for additional articulation above and beyond what the OEM bushings will allow, but as a bolt-it-on-and-go suspension kit, AEV's setup pushes flex to the limits of not only the bushings, but also the brake hoses, the wheel speed sensors, the shock mounts, front and rear fenders, and the driveshafts. If I was building a dedicated rock buggy, I could replace all of these parts, but I have yet to experience an obstacle where my Jeep's articulation has been a limiting factor.
The Corner Travel Index is the most accurate measurement of suspension articulation. I had an opportunity to test my Jeep's flex at one of MetalCloak's Skillz Day events. My Jeep's score was 735:
These tests are a great opportunity to check for problems at maximum articulation. AEV's suspension proved to be well-sorted right out of the box, and pushes everything to its limits. I found that my Jeep's rear tires kiss the end of the OEM Rubicon rock rails at maximum compression, and my highsteer drag link has 1/4 inch of clearance under the passenger-side frame rail at maximum compression. At full droop, my brake hoses and wheel speed sensor lines are stretched to their limits, so I made a small tweak to the bracket to free up a little tension. Driveshaft clearance is fine, although the joints will not tolerate much more suspension height.
Outside of a controlled environment, this simple bolt-on suspension's performance is even more impressive:
No matter how much suspension flex your vehicle has, you can always find obstacles that are extreme enough to lift a tire off the ground. However, 40 inches of articulation is plenty for the real world.
One of the great things about AEV's suspension is that it can easily be upgraded in the future. For instance, if you don't like reusing the original control arms you can easily upgrade to MetalCloak control arms. If you want to take the steering to the next level you can easily upgrade to Reid Racing knuckles and Synergy highsteer. The sky's the limit with AEV's suspension, but it performs flawlessly right out of the box.
My stated goal with my choice of suspension was versatility, and at this point the AEV 3.5 inch DualSport ST has lived up to its promise without costing an arm and a leg. It has delivered on every promise made by American Expedition Vehicles' marketing - the suspension truly improves the ride and handling on-road while tremendously upgrading the Jeep's capabilities in all off-road terrain.
Along with the suspension, I have also upgraded the steering and front axle to further enhance the Jeep's handling and strength, but these mods are covered in other blog entries. If you have any questions regarding the AEV suspension, please leave a comment below!