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Installing a JKU Budget Boost & 35-Inch Tires

Posted in How To: Wheels Tires on February 16, 2018
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No one can deny the impact that the Jeep Wrangler JK has had on the off-road world. It’s one convenient and capable package with enough room for the whole family. These vehicles have opened the door to more and more enthusiasts joining us on the trail, and that’s great for many reasons.

One question we’ve been asked more than once from a new JK owner is, “What should I do with my Jeep?” We say, “Take it four-wheeling!” Of course they mean what modifications should they make to their Jeep, and the truth is you don’t have to do anything to a JK to make it off-road well (especially a Rubicon). Sure, a few improvements can be made, but throwing thousands of dollars at the Jeep probably won’t make it much more capable if you never use it off-road. Chances are its limitations on the trails are based in the knowledge and experiences of its driver, who cannot buy those things from a catalog but rather has to earn them. As you use a Jeep off-road, it will let you know what parts need to be upgraded for what you use it for.

So when our buddy from college said he wanted to buy a new JKU, we were all for it. We told him exactly what we would do—keep it mild and use it. And while a fully loaded Rubicon is nice, you, we, and he can have lots of fun in a pretty basic JKU Sport without ever exceeding its capabilities. As he uses the Jeep (it’s also his daily driver) we can help him make improvements to the rig to do what he wants it to do much better than stock without adding any of the trendy junk that seems so common to the JK.

We did this with an eye towards spending cash where we would see the best improvements via quality components and keeping what good parts these Jeeps have from the factory in place. To that end, with a little help from our friend’s at American Expedition Vehicles (AEV), Spidertrax, and Nitto Tire, here is what we did to our buddy’s Jeep last weekend to make it more capable off-road without any compromises in on-road drivability. And as a bonus, it looks a whole lot better too!

Here’s our before shot. The Jeep looks pretty good with a set of tires and wheels off of a Rubicon, but we can do better. Our buddy Chad has also added a set of factory Rubicon sliders, and we helped him add and test a Bestop Trektop NX Glide top (
The AEV Budget Boost is simple but thoughtfully engineered. It comes with all the brackets you’ll need to lightly lift your 2007 or later JK. Lift comes from polyurethane coil spacers that space the factory springs down about 2 inches. The kit reuses the factory shocks by spacing the front shocks up from the axle and the rear shocks down from the frame with supplied spacers and brackets. The smaller black pucks and squared pieces are Delrin plastic bumpstop spacers that allow the suspension to work with the relocated shocks. Sway bar drop brackets and all the hardware you’ll need are also included. The steel parts are either powdercoated or galvanized. We found the kit online for about $285.
The suspension system from AEV comes with detailed instructions that we followed. With the vehicle on jackstands we were able to loosen but not remove some bolts and remove others (shocks, brake line retention bolts, shocks) to easily pull the rear springs out of place. That allowed us to remove the factory upper spring isolator and replace it with the thicker AEV part.
The rear shocks are spaced down using longer bolts and plated spacers between the upper shock mount T-bar and the frame. Tighten the new bolts to 37 lb-ft per the AEV instructions. Seeing the torque specs right there in the instructions is a nice touch when many instructions just refer you to a factory service manual.
The kit includes two of these rear bumpstop spacers and four bolts, washers, and locking nuts to secure the spacers to the rear axle bumpstop landing pad. This will keep your shocks happy when the Jeep gets all flexed up on the trail.
Installing the front portion of the suspension is a little bit more complicated than the rear, but not much. To start, we disconnected the lower shock mounts, the lower front sway bar mounts, and the bolt securing the top of the brake hose to the frame. We loosened the eight control arm bolts, loosened the frame-side track bar bolt, and removed the axle-side track bar bolt. This allowed us to lower the axle enough to remove the front springs. Take care not to damage the brake hoses with the axle lowered.
The AEV suspension comes with front brake drop brackets for 2007-2010 models and directs you to remove the factory brake line from this steel bracket on 2011 and later JK front axles. We used a pair of locking pliers and an adjustable wrench to spread the bracket out enough to get the hose out. Be careful not to cut or crush the rubber hose while doing this. After the kit is installed the brake line will be zip-tied to the shock to keep it from moving into the coils of the spring.
The polyurethane lift spacer goes on top of the factory spring isolator before the factory coil spring is reinstalled. These sway bar end relocation brackets slide over the axle and bolt to the lower factory sway bar mount on the axle. This keeps the sway bar level with the new lift height.
The AEV suspension comes with these Delrin plastic bumpstop spacers for the front. They require that two 3/8-inch holes be drilled in the lower spring perch. A supplied bolt, washer and nut secure the spacer to the coil spring perch once the spring has been reinstalled. The trick is to get the bumpstop spacer into the coil and then bolt it in place. We have seen folks temporarily zip-tie the spacer inside the coil before reinstalling the coil. We were able to slip the spacer into the freshly reinstalled coil.
With everything tightened back up to specification we were able to move on to installing these Spidertrax wheel spacers. The spacers are 1 1/2 inches thick and allow for wider and taller tires to clear the suspension on a lightly lifted JK like ours when running factory aluminum wheels. They install easily with one person holding his or her foot on the Jeep’s brake while the supplied thread is applied and nuts are torqued to 90 lb-ft in a star pattern. Expertly machined from 6061 aluminum, the Spidertrax wheel spacers are some of the highest-quality ones you can get. We’ve run them on several projects without a single issue.
In this day and age there are dozens of different tires we could have gone with for a JKU build like this. We like to keep things low and go with big tires, so shoving these 35x12.50R17LT Nitto Ridge Grappler tires under this Jeep is a tight fit. Truth is we had to trim the Jeep’s front air dam and may also need to trim in the rear if our friend Chad wheels this thing like he should. The Ridge Grappler is a great tire for trail and road. Nitto advertises it as a hybrid tire, a cross between an aggressive and durable mud-terrain tire and a well-mannered and quiet all-terrain. That’s what Nitto claims, and with our experience we know that’s what this tire delivers. It’s a top-notch tire for a nice Jeep.
Since we are going up in tire size from about 29 inches (for the factory Sport model tires) to 35x12.50R17LT Nitto Ridge Grappler tires, we need to recalibrate the Jeep’s computer. We chose an AEV ProCal Module ($170). The module uses dipswitches to reprogram the Jeep’s computer for larger tires and different gear ratios, recalibrate the JK’s tire pressure monitor, and more. Plus, it’s easy to use.
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Nitto Tire
Cypress, CA 90630
American Expedition Vehicles
Commerce Twp, MI 48390
Spidertrax Off-Road
Longmont, CO 80503

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