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Transformer - Part 2: Suspension and Tires
By Jim Allen
(From Off-Road Adventures Magazine)
Skyjacker’s 6-inch TTB lift is a good choice for a Ranger. It’s enough lift to fit 33 inch tires, works well on the trail yet still stays within the realm of near stock street manners. The hose clamp at the top of the spring was a little extra insurance to make sure the top of the spring didn’t come unseated the first time the truck was ‘wheeled. It turned out to be a needless worry.
The Ranger makes some major transformations in this installment. We hit two of the three major trail performance highlights in this installment, namely suspension and tires,
The best way to start a buildup is to first decide what size tires you want to run. Once you determine what size is realistic and practical, you can then go about planning the mods to compliment that choice. You have to think beyond just getting the suspension jacked up enough to fit the tires. In addition to gaining the height needed to clear the tires, you also want a suspension system that’s stout and safe, articulates well, provides good travel and delivers a decent ride.
Our Ranger’s owner, Jim Oaks, has a lot of experience with Rangers and knows that the combination of 33 inch tires, and the approximately 4-inches of lift needed to fit those tires, offers great trail performance yet provides decent street manners for a daily driver. Thus the fitment of 33s became the foundation of our buildup.
Tires & Wheels
Introduced in 1980, the BFG Mud Terrain has been a four-wheeling benchmark ever since. The BFG MT is best known for having tough sidewalls that resist damage from running aired down in hostile terrain. In addition, there’s extra rubber around the beads to protect the rim when aired down. We’ll show you how they look on the Ranger in a later installment.
The BFG Mud Terrain is a cornerstone tire in the four wheeling world that can always be depended upon to perform. This perennial favorite just keeps getting better, having been updated just a few years ago. The relatively new Mud Terrain incorporates design changes that make it more quiet and street friendly while also offering improving trail performance. It still features the 3-ply TriGard sidewalls, but a computer redesign of the tread resulted in more rubber on the ground, better self-cleaning of mud and a much quieter tire on the street.
ProComp’s Streetlock wheels were a no-brainer. Combining looks and toughness with a great price, we couldn’t go wrong. The extra ring around the outer bead, which simulates the look of a beadlocked wheel, adds a lot of extra protection to the outer bead.
Suspension: TTB Trickery
Ford’s Twin Traction Beam (TTB) front axle/suspension system is a mix of the weird and the wonderful. Though TTB is called an “independent” suspension, it really isn’t. It’s probably best described as a semi-independent suspension, essentially a much improved version of the swing axle concept you may have seen on old VW Beetles. Ford’s design goals were to improve ride and handling on the street. They succeeded in that goal at levels somewhere between a fully independent system and a solid axle. In terms of being modification friendly, it’s in the same place
Go ahead and call ‘em “fake beadlocks” if you want, we won’t kill you, but you’ll be missing the point. The ProComp Streetlocks are in a class by themselves. If you start with a stout steel wheel then add this heavy ring to the outside rim, you end up with a wheel that’s up for some abuse and looks gnarly.
TTB’s problems really begin in the world of aftermarket lifted suspensions. The main effect is on your wallet. In terms of trail performance, the end results are much better than a true IFS, but not as good as a solid axle. The results on the street are in that middle position again, behaving very “stock-like” up into the 4-inch lift range, but above 4 inches, street manners deteriorate rapidly.
The axle and differential part of TTB is near it’s equivalent solid Dana axle in terms of stock strength. When subjected to the rigors of off roading, however, the suspension part reacts very differently. As the beams drop, even on the stock setup, the toe-in increases. Camber goes positive as the suspension drops (top of tire leaning out) and negative as it compresses. Caster goes negative (pivot point of knuckle tilts forward from the top) as the wheel drops and positive as it compresses. More movement equals more steering geometry changes and thus more bumpsteer.
What is bumpsteer? It’s essentially when suspension movement causes a suspension geometry change severe enough to force the vehicle off-course and require a steering correction from the driver. The OE engineers minimized bumpsteer by limiting the TTBs travel, but even in this stock configuration a Ranger’s steering gets a touch of “wanderitis” on bumpy roads or in four-wheeling situations.
A lift may increase this tendency for the steering geometry to change during suspension movement. This is especially true if the kit offers what many four-wheelers want... more suspension travel. To minimize these effects in combination with improving travel, the lift kit should have certain features.
The changes in toe-in may have the most effect on bumpsteer, so a dropped Pitman arm, and/or other steering mods, become of vital importance to allow the travel arc of the tie rods to follow the travel arc of the beams as closely as possible. Having these parts as parallel as possible will minimize the changes in toe and keep bumpsteer issues similar to stock. With extreme amounts of travel, however, you’ll just have to live with a certain amount of extra bumpsteer and incorporate it into your driving style.
Caster changes from increased travel will also have a big negative impact on bumpsteer... more so at higher speeds. This is minimized by both dropping the aft pivot point of the radius arm and making the arm longer. Some kits offer only a dropped radius arm bracket and some have the option of longer arms. Always order the longer arms for the best performance. The dropped bracket setups are designed to operate with limited travel, usually not much more than stock. When you try to increase travel with this setup by installing longer shocks, you may actually put the suspension into a bind and increase the strain on the mounting points. Camber changes are more difficult to limit if you want more travel. Fortunately, camber by itself has the least effect on bumpsteer, at least at low speeds, so you don’t need to worry about it much. Also, don’t forget that you may have toe, caster and camber changes occurring on one side only, both sides or in some combination, depending upon the terrain. This is simply a fact of life with TTB, lifted or not.
The final element for a good TTB lift is the quality of the bracketry... especially the pivot brackets. These parts are under increased strain when lifted, so the materials and welding need to be top notch. Because dropped brackets impart more strain on the chassis, their fastenings must be of high quality as well. Making sure they are tight should be a regular maintenance chore for lifted TTB owners.
Skyjacker’s lift kits are highly regarded in the world of Ford TTB enthusiasts because they fit well, hold up and get the job done right. We opted for a full-boat, Class II 4-inch kit. Class II signifies that the kit includes new radius arms and bracketry, rather than drop brackets for the stock arms as with a Class 1 kit. We opted to upgrade the kit further with Skyjacker’s superb rear springs instead of using lift blocks. This is usually a better way to go if you are looking to reduce the potential for axle wrap. Skyjacker leaf springs are known for their good ride as well as providing good articulation.
Our final option was to go with Skyjacker’s new Platinum Series monotube gas shocks. They were just coming out at the time we started this project. They sounded good on paper, so we said, “sure” without necessarily expecting a whole lot. The reality is these top quality shocks are even better than the paper hype. They feature a 2-inch bore with an 1/8-inch wall body.A 7/8 inch, high carbon steel shaft with an incorporated polyurethane bump stop, attaches to an SAE 7075 aluminum alloy piston which features Viton seals. These are seriously beefy shocks, folks, but their price is surprisingly right. We’ll let you know how they work. Read more about Tires
Correction: In the June and July issue, the Skyjacker lift kit for the Project Ranger is a 6-inch kit not a 4-inch kit. We apologize for the Numeric dyslexia.
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