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Better Alignment & More with Aftermarket IFS Arms

Posted in How To: Suspension Brakes on April 19, 2017
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Adding lift to independent front suspension (IFS) usually raises the suspension arm angles, and puts greater angle on the stock ball joints. Other effects can include suspension binding at full droop and loss of ability to adjust to optimal wheel alignment. Aftermarket upper control arms (UCAs) can help correct these geometries and compensate for added lift due to beefier or longer springs, leveling shocks, or coilovers. They may also provide a bit more suspension travel as well, and are typically stronger than the factory units they replace.

Whenever you change a control arm on the front suspension, or you change the ride height, it’s generally necessary to realign the front end. Often small ride height adjustments may only affect steering toe-in, as the effective length of the tie rods decreases when lift is added. However, when lifting IFS from stock, simply aiming for factory alignment numbers may not get the front tracking and stability you optimally want.

Aftermarket arms may use rubber or polyurethane bushings at the frame, or some use spherical rod ends. Each has its pros and cons in use. Rubber provides the most comfort like the factory suspension, but flexes more under use, providing less precise handling. Rod ends offer greater strength and precise handling, but at greater monetary expense and increased noise transmission into the cab. Urethane bushings characteristics fall somewhere in the middle and need to be kept lubed to prevent squeaking.

On most IFS, you lose caster angle as the suspension arms droop. Caster can be defined as the steering pivot angle (front to rear) when viewed from the side of the vehicle. This loss also occurs when you lift IFS and increase the suspension arm angles at rest. With a loss of caster you often experience more road wander and less steering return-to-center when exiting a turn. This effect varies by vehicle based on the specific front suspension design. Some are more forgiving than others to increases in ride height. Aftermarket UCAs typically have increased caster in their design to compensate for increased front end lift. On a lifted truck, greater caster (in excess of factory specs) does not significantly affect tire wear, so caster can be increased to regain better tracking and control on a lifted front end.

At the knuckle or spindle, arms typically use either ball joints (as on factory arms) or spherical uniballs. Greasable ball joints, such as this one on a JBA Offroad arm, may offer longer service life or be relatively inexpensive to replace, possibly offering the best option for weekend warriors. One advantage to this setup is that replacement parts are easily available and the joints can be swapped out with the arm still on the truck. Whereas, uniballs (and rod ends) tend to offer ultimate strength at higher cost, but typically have a shorter life span as they are not usually sealed.
Mid-travel UCAs, such as this Chevy truck version from JD Fabrication, are designed to increase front end travel and strength. In this case, the stock lower arm was sufficient to provide some lift and increased suspension travel. The upper arm was replaced with a uniball version, and when combined with a longer-travel shock on a new upper mount, resulted in increased overall suspension travel. Note also that this arm uses rod ends at the frame mount to facilitate upper arm alignment adjustments.
In the case of a long-travel suspension, both upper and lower arms are replaced with longer versions, moving the end of the suspension further out from the chassis pivot point. This increases vertical wheel travel at the end of the arms. Manufacturers may use any combination of urethane bushings, rod ends, and uniballs in the arm joints to gain high angular movement and strength.

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