For those of you guys who don't know, Bob Sheaves was a lead engineer at the Jeep/Truck Engineering's PreProgram and worked there until 1993. During that time, he developed one of the first independent front suspension systems intended for a Wrangler. When asked by AllPar what his thoughts were in regards to what the all new 2017 Jeep Wrangler would have for suspension, this is what he had to say...
2018 Jeep Wrangler in depth : Suspension choices
by Robert W. Sheaves
Allpar’s owner, David Zatz, asked what approach Jeep is likely to take with the “independent suspension” Wrangler for the 2017 model year. This article is based on my engineering evaluation of various public sources, plus private discussions.
Will it really have an independent suspension?
The short answer: Yes, I believe it will have a front independent suspension, adapted from the Ram 4x4, with a live rear axle.
Why not Li’l Blue (patent diagrams above and right), which can exceed the capability of current Wrangler designs (due to the floating differential and long-travel design)? The current staff is not capable of tuning and adapting it, and lack the technical expertice to further develop it. There is no incentive for me to give away my own two generations of independent development beyond the original, and they have not got enough money to get Evan Boberg or me back to work on it. It does have a lot of advantages at minimal cost.
I expect a live axle in the rear, since it does not steer. It is cheaper to change the tubes and axle shafts than the front, with the steering issues.
An independent suspension has indirect aerodynamic benefits. One of the most turbulent area on any Wrangler or CJ has always been the gap between the fender leading edge and bumper on either side and the gap between the radiator shell and bumper, creating a swirling mass of air trapped in and around the sheet metal, causing unstable drag. Jack has closed the gaps and improved the airflow by around 10%.
Using a body mounted drive axle would also allow an overall lowering of the body, relative to the ground, for further improvements.
Narrowing the body reduces the “hole” the car has to punch through at speed, further improving the aerodynamics. The cost to narrow a live axle exceeds the cost to narrow an independent suspension, due to retooling the axle tubes, axle shafts, and steering geometry changes for the knuckles.
It would cost less to provide a front suspension and live axle link coil suspension to narrow the track, pulling the tires inside the new narrower body footprint and narrowing the fenders to lower the drag and increasing highway fuel economy.
An independent suspension would also:
•Reduce unsprung weight, helping on-road handling.
•Letting wheels react independently, so that one wheel hitting an obstacle does not affect both sides (one cause of wheel shimmy, or “the death wobble”). ◦This would also keep all four of the wheels on the ground, in most on-road and most off-road driving (within the limits of suspension travel) situations, increasing stability and control.
•Independent suspensions can generally be built as a unit and shipped to the factory, speeding installation and sometimes cutting costs.
Disadvantages include higher cost, more difficulty in increasing vertical wheel travel, reduced ground clearance when rebounding from a bump, and the difficulty of increasing ground clearance. Owners who want to modify their vehicles will find the price and/or engineering challenge to be much higher.
Looking at the Jeep Commander vs the Ram, both used a similar front suspension, but with different ball joints, slightly longer upper and lower control arms on the Jeep, different tuning, different frame attachments (changing basic geometry), and different shocks and attachments.
To sum up, I can see the changes to be:
•4 inches narrower (track width and fender change)
•1.5 inch lower body (suspension up inside the body but the same overall height)
•A 15% fuel economy improvement highway
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