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Nena Knows - How Big A Tire Can You Fit Under Your JK?

Posted in Features on March 11, 2016
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One of the most frequently asked questions I get is: “What size suspension lift do I need to be able to run (fill in the blank) tires on my Jeep?” The short answer is that the bigger you go, the exponentially more complicated it gets, so I think the least amount of lift to fit the desired tire size is the best. Although there are some variations that must be taken into account, here are my suggestions for basic modification of your JK’s suspension.


Aftermarket coil springs (left) are thicker and taller than the factory coil springs (right). These aftermarket springs are from American Expedition Vehicles.


2 inches or less of suspension lift (2- or 4-door)
• Fit 33-inch tall tires. The factory 17x7.5 wheels can fit up to an 11-inch wide tire—a 285/70/17 (metric size that measures about 33-inches) is a nice size for a small lift and is about the largest size we are comfortable putting on the factory wheel.
• Sway bar links: Upgrade to the right length to keep the Rubicon’s power sway unit in optimal position. Our favorite trick is to replace the front factory sway bar links with a set of rear factory sway bar links—just the right length for a 2-inch lift. For non-Rubicon models, I recommended upgrading to at least some form of disconnecting sway bar. This is one of the simplest upgrades, and it will deliver the most astounding trail performance enhancement.
• Shocks: Factory Rubicon shocks are usually still fine at this height, but we recommend a shock upgrade for non-Rubicon models.

A 2 1/2-inch suspension lift kit, with 285/70/17 tires on factory wheels—nice, mild modification. We used a TeraFlex suspension kit and Mickey Thompson ATZP3 tires.


2.5-inches of suspension lift (2- or 4-door)
• Fit 35/12.50/17 or 315/70/17 tires. However, this usually requires aftermarket wheels with approximately 4 1/2-inch backspacing to do so.
• Extended bumpstops so 35-inch tires won’t eat fenders
• Rear driveshaft clearance: ’12-current four-doors will need the evaporative canister relocated to keep the factory driveshaft from rubbing on it.
• 35-inch tires will rub the factory front bumper and the rear of the factory Rubicon sliders, unless trimmed or replaced with aftermarket units.
• Get longer, better shocks, especially with the weight of the bumpers and sliders you probably added.

This is a 3-inch spacer that sits on top of the factory coil spring to lift the Jeep. Often called a budget-boost, as they are less expensive than complete coil-spring replacement kits. Also note the length of the sway bar link. This has been changed to a longer one in order to maintain the angle of the sway bar arm at a 0-10 degree angle. This coil spring spacer kit is from Daystar; the extended sway bar links are from TeraFlex.


3-inches or more of suspension lift
• Front driveshaft clearance: ’12-current JKs will need some exhaust spacers to keep the front driveshaft from hitting the exhaust. ’07-’11 JKs need an aftermarket front driveshaft to avoid rubbing on the side of the automatic transmission pan. An aftermarket engine/oil pan skidplate is recommended for clearance of the front driveshaft.
• Rear driveshaft clearance: On ’12-current two-doors, you’re likely to need an aftermarket rear driveshaft just to deal with the pinion angle. On both two- and four-doors, you may need an adjustable rear track bar to move the driveshaft away from rubbing the gas tank.
• Tire size: 37s will fit on 3- to 3 1/2-inch lifts with flat fenders and bumpstops. For stock fenders, 4 1/2-inches of lift is recommended. The larger the tire, the more wear and tear on ball joints, tie rods, and all steering components, so expect to upgrade some of those too.

One of my favorite toys, “Bella” has 37-inch tires stuffed under a 2 1/2-inch AEV lift, with Bushwacker flat fenders and bumpstops to make it possible with no fender rubbing.


First Step
Straight from the factory, your JK was designed to perform amazing feats. Don’t underestimate the fun of learning the capabilities of your Jeep. Your first step should be getting dirty with your Jeep in its stock form, and then will you appreciate the investment in upgrades even more.

The evaporative canister plates on the ’12-current JKs should be relocated only about 1 1/2-inches away from the driveshaft on rigs with 2 1/2-inches or more of suspension lift. But don’t move it too far—the exhaust pipe on the other side may start to melt the canister!

Here is an evaporative canister on a ’12 (the first year with a metal plate mount) that was not relocated away from the driveshaft. The driveshaft boot clearly catches on the plate, bending the plate and tearing off the driveshaft boot.

To run 37-inch tires under the factory fender flares, you will need a full 4-inches or more of suspension lift.

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