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Old 09-26-2011, 03:41 PM
BlackRamHemi BlackRamHemi is offline
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The biggest issue I have with cutting coils is they are no longer engineered to perform properly with your 5 link suspension.
Not only is it unsafe and unstable it may get you in trouble with an insurance company if you cause a wreck and they find you "hacked" a key suspension component.
The reason Ground Force kits are the most expensive is because they "Engineer" them with specific designed progressive coils.

Here's a stock 2wd rear coil, note a very limited number of wraps

Interesting read on

The new spring layout shows the attention to details and vehicle dynamics that the people at "JTE" [Jeep-Truck Engineering] are famous for. While odd looking with its offset springs to the layman, this design shows attention to the fundamentals of vehicle dynamics.

In 1967, GM used a 3 link (as opposed to the new Ram's 5 link) coil sprung suspension. The result was that the vehicle had a very comfortable ride when empty (industry leading, in fact), but when any load was placed in the pickup bed, the vehicle became unstable and sloppy handling. This result almost sank the new trucks before they were even out of the gate (it was deleted in favor of a conventional Hotchkiss shortly thereafter). The new Ram is the first U.S. volume built pickup truck since that time to attempt to use coil springs as its primary suspension system.

The pitch of the springs shown in the accompanying graphic show how the springs are canted and "bent" at the BPL position (BPL=Body Part Loaded- this means a loading of 2 each 150 lb passengers, full fluids, and 1/2 payload all combined to be the base point of design for the vehicle) to allow the reactions to motion of the ground contact patch ("where the rubber meets the road", to use an old marketing phrase of another company) to be efficiently controlled and isolated from disturbing the ride quality and stability of the vehicle.
The UCA (Upper Control Arm) links appear to be splayed outward at the frame attachment points, providing a lateral stability to the system that, in conjunction with the track bar (or "panhard rod") keeps the lateral shift of the axle, between jounce and rebound (maximum travel up and maximum travel down- NOT "bounce" and "droop"), to the minimum arc possible. Due to the over-constrained system (more about this in a moment) the axle will travel laterally in the vehicle, through an arc of approximately 2" total, left to right. The positioning of the track bar ensures that the travel will also be split evenly from jounce to rebound, minimizing the dreaded "head toss" so prevalent in the Jeep XJ (Cherokee SUV), MJ (Comanche pickup), and early ZJs.
The side view angularity between the UCA and LCA (Lower Control Arm) indicates a long instant center, a theoretical point in space ahead of the axle, that controls the fore and aft arc the axle travels through as it goes from jounce to rebound. By having a long instant center, you ensure the axle does not change the wheelbase a great deal, affecting braking distances and geometry and upsetting the transient dynamics of handling in an emergency lane change.

Last edited by BlackRamHemi; 09-26-2011 at 03:47 PM.
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