Harry Wagner
Contributor
Reliable diesel engine? Manual transmission? Big solid axles? These are the components that make wheelers drool, and this ’01 Ford F-250 has them in the form of a 7.3L Power Stroke and ZF six-speed. But the stiff factory leaf-spring suspension didn’t cause drooling; it caused crying. Even with the Four Wheel Camper and custom CBI rear bumper and tire carrier, the rear suspension required single-digit speeds on rough roads to keep the pain to both man and machine to a minimum.
Our salvation came from Australian suspension manufacturer Old Man Emu, who know a thing or two about traveling over the rough roads of the Outback at speed. Fortunately for us, the Aussies love big American trucks and had just what we needed to make our heavy Super Duty float like a butterfly.
“Fortunately the Aussies love big American trucks”
How does Old Man Emu make old-fashioned leaf springs work so well? A lot of technology goes into each leaf, including shot peening to reduce spring stress, diamond cutting the ends to make them thinner and more flexible, and military wraps for less axlewrap and a margin of safety should a main leaf break. The springs also use bolt clamps instead of crimp clamps, and Teflon liners and graphite paint to reduce friction and provide a smoother ride. As a bonus the suspension not only rode better but also provided enough room for a set of 35-inch Pro Comp Xtreme MT2s and great-looking Pro Comp La Paz rims to put more rubber on the road and increase our ground clearance when the pavement ends.
Don’t let the “Xtreme” part of the name fool you—these tires are quiet on the street and even feature a 40,000-mile treadwear rating, but they are aggressive enough to get our big Ford through any terrain where we dare take our Four Wheel Camper. Now the only tears we are crying when we hit the trail are tears of joy.
1. We were able to complete the whole installation in the driveway in a weekend. Large jackstands from Harbor Freight Tools were placed under the chassis while another set of smaller jackstands was put under the axle, allowing the leaf springs to be removed.
2. The Old Man Emu suspension is a true system, with different spring rates and shock damping available to meet specific needs. The kit was very complete, only lacking installation instructions. Leaf springs are pretty simple to install, but we did learn some things along the way.
3. Nearly every bolt on our Ford required some heat to loosen the grip of threadlocker and a decade of use. This small propane torch made the task of removing the spring bolts and U-bolts much easier. New U-bolts are included, so they could be cut off, but the factory spring and shackle bolts are retained.
4 Not all leaf springs are created equal! Intuition might lead you to believe that more leaves result in a stiffer ride.
But when each leaf is thin and flexible and benefits from Old Man Emu’s craftsmanship, the ride of the new seven-leaf pack is far greater than the old pack with four thick leaves.
5. The Old Man Emu Nitrocharger shocks use low-pressure nitrogen and multistage valving, which eliminates oil starvation at high speed and greatly reduces heat and pressure build up. Note the metal shock boot; it protects the 0.7-inch hard chrome shock shaft.
6. A new adjustable Panhard bar is included to center the front axle under the truck with the increased distance between the frame and the axle. It is constructed with sleeved polyurethane bushings at each end and heavy-wall tubing.
7. After the track bar’s length was properly adjusted the steering wheel was out of position. Since we did not touch the tie rod, we skipped the alignment shop and just lengthened the draglink to match the Panhard bar and center the steering wheel.
8. New U-bolts are included for the front and rear. The smaller, square U-bolts are for the front axle while the larger, rounded U-bolts are fitted to the rear of the Ford.
9. We spoke with technical representatives at Old Man Emu about the weight of our Super Duty with the front ARB Bull Bar and Warn winch and the rear Four Wheel Camper and CBI bumper. They recommended an extra leaf for the rear spring pack to account for the weight.
10. With no weight on them, the rear leaf springs had significantly more arch than the factory springs and as a result were shorter from eye to eye. We had to unbolt the main leaf from the rest of the pack in order to bolt the spring to the frame.
11. Part of our issue was related to the Ford’s shackles, which required bolting to the leaf spring with the nut towards the outside before attaching the shackle to the frame. We used ratchet straps to pull the spring into position.
12. We went to our local 4Wheel Parts to mount and balance our Pro Comp tires and wheels. Brian Garcia used a Hunter dynamic wheel balancer to ensure that the combination would run smooth, even at freeway speeds.
13. The OME suspension made plenty of room for 315/70R17 (35-inch) Pro Comp Xtreme MT2 tires on 17x9 Pro Comp La Paz simulated beadlock rims. The tires are Load Range E and rated at 3,195 pounds each, so even our heavy Super Duty is no problem for the Pro Comps.
14. A 35-inch spare would not fit in the stock location under the Ford, so a fullsize Xtreme MT2 and La Paz rim were mounted on the custom CBI tire carrier on the back of the Super Duty where they are easy to access.
By the Numbers Before (Leveling Kit, 255/85R16 tires on stock rims) After (Old Man Emu suspension, 315/70R17 Pro Comp Xtreme MT2 tires on 17x9 Pro Comp La Paz rims) Approach Angle (degrees) 41 50 Departure Angle (degrees) 26 34 Front Diff Clearance (in) 9 10 Rear Diff Clearance (in) 83⁄4 91⁄2 Front Wheel Arch (in) 37 423⁄4 Rear Wheel Arch (in) 393⁄4 451⁄4
