One thing to always check on Ford Twin I-Beam suspensions is ride height. If the front tires show camber wear and the ride height is below specs, you can bet the springs are sagging. And since the springs play a critical role in determining ride height (which affects camber), it does not make much sense to make a camber correction until the underlying problem has been fixed. The trick here is to replace or shim the sagging springs. If that fails to bring camber back within specs, you will have to do the following:
If the Twin I-Beam axles are the forged variety, which were used from 1965 through 1981, camber can be corrected by bending the axle with a hydraulic ram. To make a make a positive camber correction, a rigid work beam is slung under the axle from a pair of clevis blocks. A hydraulic ram is then placed under the middle of the axle. When pressure is applied, the ram bends the axle upward and tilts the knuckle down to increase camber. A slight amount of overbending is usually needed to compensate for spring back in the axle. A negative camber correction is made by removing the outboard clevis block and inserting a spacer between the work beam and axle. The hydraulic ram is then repositioned directly under the inner axle bushing. When pressure is applied, the work beam bends the outer end of the axle up which tilts the knuckle and decreases camber.
In 1982, Ford introduced lighter stamped steel axle Twin I-Beam suspensions on the F100 and F150 pickups. The same axle is also used on 1989 and up Ranger pickups. These axles should not be bent because doing so may weaken them. Camber corrections on the stamped steel Twin I-Beam axles can be made by installing an offset bushing in the upper ball joint. Before you replace this bushing, though, note its position and amount of offset (if any). This will help you determine how much additional offset is needed. Many aftermarket manufacturers offer zero degree sleeves which can be installed to zero out the ball joint stud location to a nominal centered position. After replacing the bushing, steer the wheel by hand to make sure the ball joint is not binding.
Caster corrections on Ford Twin I-Beam suspensions can be accomplished one of three ways: by replacing the same upper ball joint bushing as above on the 1987 and later applications, by replacing the radius arm bushing where the radius arm connects to the frame with an offset bushing, or by installing offset cam bushings where the through bolts attach the radius arms to the axles.
Another thing to watch out for on Ford F150 2WD pickups with the Twin I-Beam front suspension is rear ride height. Ford says any deviation in rear ride height with respect to stock ride height should be taken into account prior to aligning the front wheels. If the bed of the pickup sits higher or lower than stock because of helper or overload springs, or because of modifications that have been made to the vehicle (a wrecker, dumpster, towing a fifth wheel trailer, etc.), then the change in ride height and frame angle need to be computed to compensate for its affect on front caster and camber. Refer to a Ford manual for the ride height and frame angle caster/camber correction chart.
Ford says that modified trucks such as wreckers, dumpsters, trucks used for towing, and so on should be aligned to an "average" setting half way between a loaded and unloaded condition. To do this, ride height has to be measured with the truck loaded and unloaded. Subtract the loaded ride height from the unloaded ride height, divide the difference by two, add this amount to the loaded ride height, and then compare the number to the stock ride height to calculate the amount of compensation for camber and caster settings. Or, measure rear ride height loaded and unloaded, split the difference, then load the truck with just enough weight or tie down the rear suspension so rear ride height is at the mid-point. Then align the front wheels to the preferred specs.
When aligning a Ford truck that has rubber bonded socket (RBS) tie rod ends, loosen the tie rod stud, break the taper and allow the tie rod to center itself if you change toe more than 1/16 inch, otherwise you will get memory steer.
On 1980 to 1992 Ford Broncos and F150s, and 1989 to 1992 Ford F250s, a condition known as "recession steer" may be encountered. A left drift or pull that occurs while braking but produces no torque or pull in the steering wheel may be caused by the left radius arm front pivot bushings. It is important to make sure the pull is not due to a sticky brake caliper or contaminated brake linings. If the brakes appear to be working normally but there is a definite pull to the left when braking, the radius arm pivot bushings need to be replaced. Ford says it is okay to reuse the original nylon rear bushing spacer and rear bushing unless excessive wear is found. Torque the radius arm nuts to 80-120 lb. ft. Toe should be also be checked and reset to 1/32 inch toe-in.
If a pull still exists after replacing the radius arm pivot bushings, many aftermarket manufacturers sell offset radius arm bushings which allow you to change caster to eliminate the pull.
The newer Ford truck suspensions have pinch bolts which simplifies removal of the ball joint bushings. But do not assume the OE bushing has a zero degree offset. Many have 1 to 1-1/2 degrees of offset, usually in the camber direction. So if camber/caster corrections are needed, note the marking stamped on the OE bushing when it is removed so you can determine how much additional correction is needed. The first set of numbers stamped on the sleeve indicate the amount of caster, and the second set of numbers indicates camber. Subtract the numbers from your alignment readings to determine how much additional correction is needed.
Another way to figure how much correction camber/caster correction is actually needed on these applications is to pull out the OE bushing, install a zero offset bushing, then recheck the camber/caster readings to see how far they are off from the preferred specs. Any corrections would then be made by installing an aftermarket bushing with the required number of degrees of offset.
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