Choosing a suspension in today’s market is tough, as there are a lot of quality suspension systems to pick from. From shocks to springs to brackets, everyone is working hard to build the best. When choosing our suspension for Project KR (introduced in the August ’11 issue) we started with the requirements necessary for a Ford F-250 King Ranch 6.4L Power Stroke 4x4.
| Everything is included for a complete lift: Rancho Suspension system with radius arms, 325/65R/18 BFGoodrich All-Terrain tires, and Centerline Scout 18x9 wheels.
Tire size dictates the amount of lift necessary for clearance, and the taller the tire the more negative effect there is on acceleration, braking, fuel economy, agility, and unsprung weight. This is where the balance comes in: too tall and the truck gives away overall performance, not tall enough and the truck suffers in the off-road arena with low-approach angle and limited powertrain clearance. To give ourselves flexibility, we determined that tire diameter should be between 35 inches and 37 inches, requiring a lift of 5 inches for clearance. We wanted the suspension to use new radius arms to keep the pivot point close to the frame in the stock position.
Rancho Suspension has what we needed in kit number RS6514. While it was advertised as a 4-inch lift, we know Rancho Suspension is conservative with its numbers and its installation sheet stated 37x12.50R17/D BFGoodrich All-Terrains were installed on a 17-inch wheel with 6.25-inch backspacing during the development of the kit. Rancho includes the company’s radius arms, pitman arm, track bar bracket, bumpstop spacers, brake line brackets, carrier bearing spacer, hardware kits, and everything necessary for installation. The shocks in both the front and the rear are the new RS9000XL series with the large 2.75-inch body.
For the tires, we went with BFGoodrich and its All-Terrain in the new LT325/65R/18/E size. This new tire has an impressive spec sheet. It’s 13.0 inches wide on a 9.5-inch wheel, with a 3,860-pound max single load with 65 pounds of air in the tire, and it has an overall diameter of 34.6 inches. Tread pattern is in the middle for both street and off-road applications, offering a quiet and smooth ride. For the wheels we went with Centerline, whose wheels are rotary forged using T-6061 aluminum and made right here in America. Once you witness the rotary-forged process you’ll understand why these wheels are so strong. The Scout from the Wilderness line was the look we wanted, with an 18x9-inch size, 4.5-inch backspacing, and a 3,200-pound rating. Centerline offers the wheel in either chrome or polished, and we opted for the polished process so we can touch up the polished wheel.
| 2008 Ford F250 Project Kr Part Two f250 Right Side View
Once we had all the parts, we wanted an experienced shop to do the installation. So we turned to Off Road Unlimited in Burbank, California. Owner Maurice Rozo and his qualified crew have been building and manufacturing quality off-road vehicles and parts for a long time. Installing the Rancho Suspension lift kit is an easy task for this experienced shop.
Review
Once we had the suspension installed and the alignment completed, it was time for some evaluation. Rancho Suspension does not make a dual shock kit for the front of ’08-and-newer Ford Super Dutys. A single shock per wheel kept the truck riding nice at trail speeds in the off-road environment, but when we pushed it beyond an easy ride the shocks became overworked and started to fade. We replaced the front shocks with a pair of Pro Series remote reservoir shocks with a noticeable improvement in fade resistance.
| 13 Once the radius arm was in place, we were instructed to not tighten it until the vehicle was at normal ride height. Using thread lock, we tightened the bolts to 222 ft-lb.
With that being said, the suspension works great. We played around with the valving and found we liked Level 5 in front and Level 2 in the back when the truck was lightly loaded. If we were hauling a medium payload, we preferred the rear shocks set at 3 or 4. We drove the truck 1,500 miles to allow the coils to settle and then measured the lift and saw that it boosted the truck up 5.25 inches (we measured the distance from the center of the axle to the fender lip).
The BFGoodrich All-Terrain tires have proven themselves as sturdy stock, as time has only seen subtle changes in the tread. Here is a quiet off-road tire that works great for the highway yet has strong sidewall control and good traction for off-road use. The tread pattern limits you in muddy situations, but it is impressive how well these tires work when you have momentum. As for the wheels, Centerline’s rotary-forged process gave us strong, light wheels that balanced with minimal weight. Keeping the unsprung weight to a minimum helped the handling of our Ford F-250.
| 14 The new bumpstop extender was placed with a new bolt supplied in the kit. Again, thread lock is applied.
