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2008 Jeep Wrangler JK Rubicon - Trailrunner

Posted in How To on November 1, 2010
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The Trailrunner '08 Jeep Wrangler JK Rubicon crawled slow and went fast. As mentioned in the first installment, we still needed to find the perfect coils. We also had an issue with the ESP/BAS/Traction Control.

JK Wranglers are sensitive to suspension changes and steering wheel position. If everything isn't right, the Traction Control light (vehicle with two squiggly lines) illuminates when going around corners and the ESP activates. Usually, making sure the steering wheel is centered takes care of this issue and always has in our past JK projects. Trailrunner was a different story. The light illuminated while the brakes were applied automatically and the engine cut power around almost every corner! We tried every trick, including installing a set of adjustable shocks and turning them to max stiffness. We also used our AEV ProCal to find exact steering wheel center. The TC light still illuminated and the Jeep automatically cut power and braked. It was annoying.

We disabled the ESP, etc., by turning the wheel to the right, center, left, center, and holding the ESP button in at each position. This took care of the problem, but we wanted everything to work as designed and be able to leave the ESP/BAS Traction Control on. Something else was needed.

John Williams has opened Impulse Off-Road in St. George, Utah. He graciously offered his help and the use of one of his lifts for Trailrunner Part II. JKs have longer control arms that sit at less angle than TJs do. Because of this, we thought the factory-length arms would be fine. We noticed, though, that the two-door Wrangler had a propensity toward oversteer and, every time it happened, the ESP would do its thing. Teraflex offers its Elite LCG Long Arm suspension system for the JK. Its TJ long arm suspension works so well, we decided to use it on Trailrunner and see if it would cure our problems. A call to Quadratec had almost everything coming our way, except the new Teraflex 2.5-inch coil springs.

Curt Hildebrand of Teraflex had a set of muddy, used prototype 2.5-inch coils he let us use. We also procured a pair of Teraflex SpeedBumps. Parts of the Elite LCG suspension system aren't designed to run with such short coils. The rear SpeedBumps are too long and the bent lower arms, which work so well with taller coils, hit the frame when the coils are compressed. We'll be addressing the issue soon. The long Teraflex arms installed as designed, as did their new heavy-duty front track bar.

We had a problem with the steering knuckle. Someone before us had drilled too big a hole in the steering arm for a drag link flip. We had tried a Teraflex tapered sleeve, but even that innovative part didn't work (the hole was too large). We called around, looking for a new passenger-side outer knuckle, but couldn't find anything until we called the crew at Off Road Evolution. As usual, they had one and shipped it right away. Off Road Evolution has everything, including unsurpassed customer service.

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The Teraflex coil springs were the perfect height and rate for our project. After installing and removing, cutting, adding spacers, etc. to many other coils, it was great to find a set of coils that did exactly what we wanted. The Teraflex Elka reservoir shocks were the perfect match for the coils, too. With the suspension installed, the JK drove better than any we've ever driven. Really. We reactivated the ESP/BAS/Traction Control to see what would happen. Nothing did. The TC light has yet to illuminate, so the long arms have cured the incurable. The short wheelbase's oversteer is markedly reduced, too.

The porky JK needs all the help it can get reducing weight. To this end, we removed the muffler skidplate and tire carrier bumper. A bolt-on Kevin Hawkins tailgate spare carrier was rescued from obscurity and we borrowed a prototype Hanson aluminum rear JK bumper that was built for a SEMA rig in 2006. We called the new owners of Hanson and asked if they were planning to build this lightweight rear bumper and were told no. Pity, because the regular Hanson rear bumper weighs 89.5 pounds and the aluminum model weighs just 37.

We changed tires. Our Goodyear MTR with Kevlar tires worked well in the backcountry and provided arguably the best lateral traction available today. However, three of our MTR with Kevlar tires took too much weight and still didn't balance perfectly. One broke our all-time record for balance weight called for, requiring 32 ounces. Another called for 22 ounces and the third required 20 ounces. The fourth tire asked for 7 ounces, so it wasn't so bad. There's no excuse for tires to require this much weight to balance in 2010! We replaced them with a set of 37-inch BFGoodrich Mud-Terrain T/A KM2 tires mounted on the same Black Rock Viper alloy wheels. The BFG that replaced the 32-ounce Goodyear took 5 ounces to balance and the BFG that replaced the 22-ounce tire only took 1.5 ounces.

Without the help of Impulse Off-Road and John Williams, our JK wouldn't be what it is today. It's working much better now that we've surmounted the ESP/BAS/Traction Control issue. There is still some work to do, such as installing rear bumpstops and straight lower control arms, but Trailrunner is working as planned: well.

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