Was it the springs? Was it the installation? Was it the combination? Within a two week period, I had experienced two emergency repair situations with leaf springs; overall, two broken and two bent springs. The suspension was a not performing as it should. 4x4 isn't much good without a functional suspension system.
The “Spring Saga” began with “Options for the height challenged” which was a spring-over lift for my 1994 Jeep YJ. As I was replacing a 4 inch spring lift, new springs were necessary. The basic lift components were Rubicon Express and I opted for Rubicon Express springs which provided 1.5 inch of spring lift in addition to the spring over lift. And, I was able to remove the two inch body lift and still clear 35 inch tires.
While the combination was a great performer on the articulation challenges of Ocotillo Wells SVRA, a major deficiency was soon apparent. After the breaks and emergency repairs, serious questions were in order. Why should brand new springs break and bend that easy? What is it about a spring-over that created this situation?
After some research into spring philosophy and construction techniques, it became clear that springs are like opinions. Everyone has one and they are different. But, there are no wrong answers; only wrong situations.
As a recap, the Rubicon Express springs provided great flexibility; however, lacked durability. My temporary repair used the basic RE spring pack with a slightly thicker main leaf. In the long run, was the answer a thicker main leaf?
I turned to the experts at Deaver Suspension for their solution. My original 4” spring lift was built by Deaver Springs and I was very happy with that configuration. And, Deaver has been building springs for over 100 years. And, Deaver is well respected in the desert racing community for building a quality product that can withstand the rigors of a Baja race.
And the solution.....
As with anything, it is a matter of trade-off to fit a specific situation. While important, high numbers on a RTI ramp were not my goal. Of prime importance was durability and dependability. Flexibility and a high RTI number mean nothing if the flex is a weak link and leaves you stranded in the desert.
So, what caused my original problem? A combination of thinner springs (great flexibility) and flexibility that was over extended in the wrong direction. Springs work best when they have a drop length. When they are inverted in a negative arc, bad things can and do happen to springs. In my case, the springs experienced a negative arc that could have been prevented by a simple lowering of the bump stops.
In other words, the spring-over lift provided over 4 inches of lift while retaining the stock bump stops. As such, a simple lowering of the bump stops may have prevented much of the negative arc which lead to the bending and breaking. But, that was not the complete answer. It is all about trade-offs where you “tune” to meet your situation.
As desert wash running provides a different stress on springs than rock crawling, a different construction of spring pack is required.
Enter Deaver Suspension and their experience in building durable spring packs for desert racers. Their technique starts with a military-wrap main leaf and accomplishes “lift” by adding additional leaves to the pack. And, each leaf provides support for the upper leaf. In other words, most springs depend on main leaf arc to provide lift or flexibility. However, the “flex” should be more a function of the axle weight providing for a drop rather than having to also overcome the spring arc.
In short, Deaver is noted for a quality spring pack for desert race trucks. They have been moving their experience to provide durable spring packs for the 4x4 market with support for Broncos, Jeeps, Toyota Tacoma and a variety of other vehicles.
For my configuration, a 10-leaf pack provides about 2 inches of lift on top of the spring-over. And, the progressive rate spring provides plenty of flexibility.
But, the key is bump-stop positioning. Deaver fabricated some bump-stop extensions to which are mounted 4 inch bump-stops. That places the bump-stop in close to same position (distance from the spring) as a stock configuration. That will stop excessive negative spring arc. A brief test in the shop was inconclusive to show flexibility on the rear axle as the Skyjacker 5th link used to prevent axle wrap also limits some extreme flexibility.
A brief trail test proved satisfactory results with respect to articulation and smoother ride than would be expected with the 10-leaf spring pack. Durability will be proven after several desert wash trips over time.