Setting Suspension Preload
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~Tech Page Glossary~

Kevin $laby
Tech@BaselineSuspensions.com

Mustangs! Center the Rearend under your car!!!

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2 Methods for
Zero Suspension Preload

*All measurements should be done in race trim with the driver sitting in the car and with the suspension loaded.
*The car should be blocked up with 4 stands under the Frame (front and rear) AND the Rear Control Arm Axle Mounts (this allows the axle housing to rotate freely). Removal of one upper control arm is necessary and if the car is not equipped with a track locator then the car body or axle housing may move sideways which can throw off the control arm lengths and induce Preload.


~Method 1~

1. Remove one bolt from Passenger side Upper control arm and let control arm hang loose. Make sure the car body or axle housing does not move sideways when bolt is removed.

2. Place angle finder on pinion yoke.

3. Loosen both jam nuts on Driver side Upper control arm and Shorten or lengthen until the desired pinion angle is achieved. Generally, Shortening the control arm INCREASES the pinion angle and Lengthening the control arm DECREASES the Pinion angle. Make sure the car body or rear end does not move sideways when the control arm is adjusted and verify that the rear end is still centered side to side in the fenders.

4. To eliminate Preload on a Race Car: While the driver is in the car, shorten or lengthen the Passenger Side control arm until the bolt lightly slides into the chassis hole then fully tighten all jam nuts. If the driver is sitting in the car when this is done then there will be zero pre-load on the rear suspension while sitting on the starting line. If a positive or negative pre-load is desired then the Passenger Upper Control Arm can be lengthened or shortened up to 1 full turn but no more. I do not recommend adding any pre-load at this time. If the car does not launch straight with Zero preload then pre-load can be changed if necessary.

Note: Rubber bushings in the control arms may induce some preload and may take some time to get the desired pinion angle due to bushing flex.


~Method 2~

*This method does not remove all preload but it is minimized as long as the car is fully loaded in race trim.
*All measurements should be done in race trim with the driver sitting in the car and with the suspension loaded.
*The car should be blocked up with 4 stands under the Frame (front and rear) AND the Rear Control Arm Axle Mounts (this allows the axle housing to rotate freely).

1. Remove and adjust both upper control arms so they are the same length then re-install control arms.

2. Place angle finder on pinion yoke.

3. While both control arms are connected to the chassis and axle housing, loosen both jam nuts on BOTH control arms and Shorten or lengthen each control arm EQUALLY until the desired pinion angle is achieved. Tighten jam nuts when done.
*Equal turns on each bar must be done to minimze the possibilty of inducing more Preload.


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