Improving Ground Clearance And Ride Quality
In my opinion, right out of the box, the JK Rubicon model is arguably the best all-around OEM Jeep ever offered to consumers. As you can see in every off-road catalog, its available enhancements cover every aspect of possible improvements. One of the players in this JK parts frenzy is Rancho Industries, which offers its new 4-inch JK lift kit, and of course it's proven RS9000 adjustable shocks. Equipping a JK with a 4-inch Rancho lift kit and RS9000 shocks can give you a foot of clearance, room for bigger tires, and an improved ride both on and off the road.
According to Jeep information, 35-inch tires will fit under the JK's fender flares and on its spare tire carrier, and will clear the rear bumper as well. This may well be true, but not with Jeep OEM wheels with their inward offset, so I didn't want to try larger tires without first raising the Jeep. Since Jeep lists the ground clearance for a Rubicon as eight inches (not including the two center pumpkins of the Dana 44 axles), the Rancho 4-inch kit will give you a full foot of clearance. Remember, when you drop air pressure for improved traction, you lose some of those original eight inches (you can lose as much as two inches if you run really soft tires). A 4-inch lift could be the difference between a holed and leaky gas tank—sometimes difficult to get home that way—or a few scratches in the tank's paint.
It's amazing to me that Rancho's suspension engineers know to the fraction of an inch just what the springs' tension, strength, and bar diameter must be to produce exactly four inches of lift to a JK. But that's exactly what my JK Rubicon was lifted at each corner (original measurements were: left front, 35 1/4 inches; right front, 35 inches; left rear, 35 1/2 inches; right rear, 35 1/2 inches. Final measurements before the addition of the 305/70R17 Goodyear MT/R tires with Kevlar: left front, 39 inches; right front, 39 inches; left rear 39 1/2 inches; right rear 39 1/2 inches). All measurements were taken at the center of each fender flare. The Goodyear tires added another full inch to the total ground clearance. OEM Rubicon tires are 32-inch diameter, while the Goodyear tires are 34.2 inches in diameter. With the switchover to 17-inch diameter rims and the 5x5-inch lug pattern in 2007, tire and wheel companies were forced to fill the void as quickly as possible.