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Setting Up the Geometry
Prior to installing this 4 inch air spring lift system I took some measurements at the four corners of my Jeep. I wanted to know the exact height I had to start with so I would know how to get to the height I wanted, 3 inches above stock.
I had 2.5-inch coil springs in the front, and 2-inch spring spacers in the rear. What I needed to set my ride height at 3 inches was an additional 1/2-inch in the front and 1 full inch in the rear.
Before attempting to set up any of the geometry I cycled the air springs through their full motion several times. My thought was to work out any kinks and identify any binds in the suspension components. I?m not at all sure this did anything but I have to say it sure was rewarding and fun to do!
It is important to realize that the four-inch lift AiROCK system is sold to be installed on a Jeep that already has all the steering and suspension components needed to support a 4-inch lift. Mine did not so I had to add a few items.
After cycling the air springs a half dozen times I set the ?ride height? to 3 inches, even though the system is designed for 4-inches.
I am not looking for height, only enough to clear my tires and the obstacles I normally wheel. Height for me is not a good thing. Maintaining all four wheels pointing down is.
Setting the ride height to 3 inches involved an air pressure of 52 PSI in the front air springs. Bring the rear up to 3 inches required 55 PSI of air.
3-inches above stock is where I want my everyday on and off road ride height to be.
Rear Track Bar
Prior to this installation I was running a stock rear track bar located in the stock location.
It didn?t take long to realize this wasn?t going to work. I elected to install a Rubicon Express Track Bar Relocation Bracket.
This bracket raises the frame mount end of the track bar about 4 inches. This worked great. My rear axle is now centered within 1/8-inch of perfect. I can live with that.
Front Track Bar
I replaced the front track bar with a Currie Adjustable Unit with the Johnny Joint. I have to say, this is one heck of a heavy-duty bar. I also feel this contributes to an improvement in my Jeeps ability to flex.
With the help of my friend Jon we centered the front axle within the same 1/8-inch difference.
Note: In cycling the front suspension I found my front differential skid plate lightly hitting the Johnny Joint (frame) end of the track bar. This issue was resolved by clearancing the skid plate just a bit.
Pinion Angles
Once the axles where centered under my Jeep and the Jeep was sitting at the 3 inch ride height I went about setting the pinion angles.
This was easy!
Both the rear and front pinion angles where well within tolerances. Both were less than 3 degrees at the 3-inch ride height. Part of this goodness clearly belongs to the long drive shafts connecting to the Atlas T/Case. Three degrees is more then good enough to handle drive shaft speeds of 5,000 RPM
I raised the Jeep to its maximum height to see what kind of angle I would get. The front went up to 7 degrees and the rear to 6.5. I can live with that during temporary situations off road.
In the future if I find the need to go up to 35-inch tires I will probably replace the lower rear and upper front control arms to adjustable units. I may do this now anyway to get the benefits of eliminating the stock arm binds. We?ll see.
Steering Geometry
Once pinion angles where verified and with the Jeep sitting at the 3-inch ride height it was time to set the steering.
I set the toe to the standard 1/8-inch toe in. I did this using the ?measuring tape to tire mold mark method? as this seams to have always worked well for me.
Once the toe was set I centered the steering wheel by adjusting the drag link collar. No brainier here.
I have no personal means of setting caster so I will be bringing it into a friends shop when I get back from vacation for this. I do have adjustable lower control arms in front, but I also have the cam adjustment to set the caster. Hopefully there will be enough left in those cams to set it up correctly.
Other Geometric Conditions
Once I get the chance to fully evaluate this system both on and off road I will be making a few more changes.
I generally do not like to make multiple changes at the same time as it muddies up the water in trying to understand what change had what effect on how my Jeep performs.
I do have a Currie Anti-Rock that is going to be put on very shortly.
There is a total of 9-inches of travel in this suspension, full compressed to full droop. I have discovered the rear sway bar links to be two inches too short. These will be replaced.
I plan to order the parts to replace these links with the hiem joint type links as describe on Stu Olson?s web site.
In all likelihood I will replace the four remaining stock control arms with adjustable and more flexible units.
That?s about it for now folks. I think I have covered what was required to install this system, and what my initial impressions are. I have a vacation coming up. But I will be back a week from the coming Sunday to wheel the Natural Bridge trails. I will be sure to report back on how this change performs on obstacles that are well known to my Jeep.
The apples to apples comparison, even with my interpretation should be interesting.
Have a great evening folks,
Frank
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