Since the article in Overland Journal came out, I’ve been asked about my rear suspension numerous times. Perhaps I should go into detail here, as it’s not top secret and it isn’t that fabulous.
Here’s the set up:
- Add-a-leaf spring pack, advertised as 3” of lift
- Extended shackles, advertised as 1.5” of lift
- Old Man Emu shocks, N85
- Firestone Ride-Rite air bags, kit #2403
- Measurement: 23-3/4” from hub center to fender sheetmetal (essentially unloaded . . . for this truck, anyway.)
The question: why all this crap?
Originally, the shackles were my first addition to the rear and meant to complement the front lift. Here’s the problem with extended shackles: they negatively affect the spring rate of leaf packs – it’s not conjecture, but fact. You need a nice 90-degree or slightly acute angle of the shackle to the datum line to maintain the spring rate of the packs. But the problem is that you’re changing to longer shackles, but not longer leaf packs. Ultimately, extended shackles are going to work better with longer leaf packs.
In my case, I packed in a lot of weight over the rear axle with gear, and
behind it (read Tom Sheppard’s article about loading lashing?) with the heavy bumper tire carrier, and those lift shackles did more harm than good in this scenario.
Now, I
should have just purchased some custom leaf packs made by a local spring shop and I'd be living happy. Concerned about the possible heartaches and downtime involved with custom packs, I located the add-a-leaf packs and installed them instead. It’s fine, but not ideal – especially with the longer shackles. AALs (add-a-leaf) force the OE packs with a little more arch thereby creating lift.
Neato. Well, that pulls the lower part of the shackle toward the front of the vehicle – again, reducing the spring rate with an obtuse angle (datum-to-shackle), and those springs are already a piece-meal solution. Certainly not designed for all this activity and stress, right?
Here come the air bags, a cork for a hole in my bucket. I like these. Very effective device for managing additional load
and for daily driving. Just pack her down with food, water, and equipment for a long trip and shoot a few PSI into the bags. They are limited in down travel, so I wish I could get a larger bag. Nevertheless, I’d rather have good handling over wild suspension articulation any day of the week.
I plumbed the two bags together, so they act as one system sharing the air and there’s only one valve. As one side of the axle cycles upward rolling over obstacles, it squeezes the air volume over to the other bag 9as this one stretches out. Stick with me on the theory here: PSI remains the same so this doesn’t diminish handling noticeably. (you’re free to test drive this truck on the trail if you’re curious). We could probably discuss the merits and disadvantages for a while, though.
The shocks I selected are the N85, but they are still a little too short.
While the system works fine, actually pretty well, I like to point out the deficiencies and be aware of them. No suspension is perfect for all situations. But I’ll keep tinkering with it until I feel like I’ve come close.
Keep on.