Once we find the wheel rate of the bar, we convert that rate back to the end of the arm using the sway bar installed motion ratio and we will then kow the true bar rate at the end of the arm. This rate could be close to the calculated and/or published rate for that particular bar, or it could be much different. In any case, this method cuts through all of the unknowns and gives us the true numbers.
Getting Started We start off by doing the following steps to prepare to take the measurements we will need to determine the sway bar wheel rate.
1. Install the desired bar and arms and leave loose to the lower control arms. Make sure that the link attaching the bar to the right lower control arm is perpendicular to both the sway bar arm and the lower control arm. This is very important and can affect the motion of the bar.
2. Remove the front springs and support bot of the front corners of the car with solid links in place of the shocks. Make sure that the material used for the links is strong enough to support the weight of the car. We usually use tubing of0.75 to 1.0 inch in diameter with nuts welded onto the ends and Heims attached with opposite threading so we can easily adjust the length without removing them.
3. Support the rear of the car at one point, usually using a piece of angle iron placed on top of a stack of wood or other medium and placed at the center of the frame preferably behind the rear-end and halfway between the rear wheels. You will need to support the rearend using either solid links like at the front or by placing ride blocks between the axle tubes and the frame if it is a frame-under car. You can remove the wheels to provide more room for chassis roll.
4. Place the front wheels onto scales and record the RF weight.
Before taking any measurements...
Before taking any measurements or weighing the car, lock the steering shaft with the wheels pointed straight ahead. Movement of the steering and wheels will negatively affect the results. We used opposing locking pliers to hold the steering shaft.
You will need to support the...
You will need to support the rear of the car at one point in the middle between the two rear wheels. We used a section of large angle iron placed on the crossbar behind the rearend.
Before getting ready to support...
Before getting ready to support the car on the sway bar, snug the left arm up against the lower control arm, but do not pre-load the bar. When measuring the static loading on the RF wheel with the link installed, make sure the bar arm is loose.
5. Support the frame at the RF on a jack and remove the link. Record the weight of the wheel assembly, or unsprung weight, of the RF wheel. We only want the sprung weight number when calculating the amount of deflection related to the load the bar will support. Move the assembly up and back onto the scales several times to take the friction out of the pivots.
6. Subtract the RF unsprung weight from the total RF weight to find the sprung weight that the bar will support. Record that number.
7. While the link is out and the load is off the RF wheel, we will measure the shock motion ratio. Measure the shock length (the distance from the center of each of the mounting bolts) for the shock with load on it.
8. Place a flat block of wood orother material under the RF tire.Remeasure the shock length. Divide the amount the "shock" moved by the height of the block placed under the tire. Example: Ifthe block were 2.0 inches thick and the shock moved 1.0 inch, then our motion ratio would be 0.500. We will use this number later on.
9. Remove the block, put the link back in place, remove the jack and let the front wheels rest on the scales. Snug up the sway bar arms against the left lower control arm being careful not to pre-load the bar. Record the RF ride height from the frame to the floor. We will need to maintain this height throughout the test.
10. Record the weight on the RF scale pad to make sure it is the same as in step No. 4. Jack up the RF corner carefully and remove the link. Let the RF corner back down onto the scale so that the sway bar is supporting that corner's weight. The frame will be lower and we need to get the ride height back. Measure the RF ride height now and subtract that number from the static ride height we measured in step No. 9.
11. Shim under the RF tire the same amount that the RF frame dropped so that we will be back to the original ride height and no load transfer from chassis roll will have taken place. The scale weight should be the same as in steps No. 4 and No. 10.