Air Lift 5000 Ultimate Bags w/ Daystar Cradles
Updated: Aug 16, 2018
It was apparent, after loading up the camper for the first time, that the rear suspension of the truck in stock form, even rated at 4,400 lbs of payload, was not stiff enough to handle the weight of the camper. After taking sag into consideration, the rear of the truck was sitting 0.5” lower than the front, definitely not ideal. A nose high vehicle indicates more load on the rear of the vehicle, unweighting the front wheels (poor steering and braking performance) and messing up headlight alignment (poor visibility and blinding oncoming traffic). This was a condition that would only get worse once we were loaded up for a trip and must be corrected before hitting the road.
There are several solutions out there on the market, some of which include air bags, add-a-leaf kits, and Torklift StableLoads. Each has their plusses and minuses, airbags are infinitely adjustable within their range and can be plumbed independently, but, they require access to an air compressor, often need > 5 psi in them at all times to prevent damage, and are prone to parasitic pressure loss. Add-a-leaf kits will increase spring rate, but are non-adjustable and are a pain to install. Torklift StableLoads are a simple and robust solution, but can be cumbersome to adjust and only have so many adjustment points.
I chose airbags for our vehicle due to the infinite adjustability and their relative ease of installation. In the air bag world there are two names, Firestone and Air Lift. They both offer quality setups that are comparable in price. I went with Air Lift primarily because their bags have internal jounce bumpers that eliminate the need to maintain > 5 psi at all times, especially helpful when there's no load in the bed and I want to run no pressure in the bags.
The Air Lift kit is well designed and comes with all required hardware to install and plumb the bags. Before I get any further into the installation, I'll note that I installed the kit alongside a set of Daystar airbag cradles. These are a contentious inclusion and are mentioned by the manufacturer specifically as a modification that will void the warranty. So why add them? Simple, with stock the Air Lift kit, the bag is constrained between the upper mount at the frame and the lower mount at the axle. When the axle is fully drooped out, the bag is helping to carry the weight of the axle as well as potentially restricting the amount of travel. By eliminating the hard mount at the lower axle and instead replacing it with a cradle, we get all of the load carrying capability of the bags, but the two uncouple when the axle droops. Neat right? Anyway, a few modifications to the kit are required to fit the cradles, but I'll get into that later.
The Air Lift instructions do a very good job detailing the installation procedure, and the kit will install with basic hand tools. First step is to remove the stock bump stops from the frame and bolt on the Air Lift bracket.
With those out of the way, we can begin doing mockup with the kit. Since I knew I was installing the Daystar cradles, I deviated from the instructions a little bit. On the lower axle mount plate, there is currently no hole to secure the cradle, I needed to add that. After fitting the bag to the upper mount, and affixing the lower mount to the axle, I was able to place the cradle on top of the lower mount and adjust its position to it was centered on the bag at ride height. Note, the cradle will not be centered on the mount, it is offset inboard. With the cradle in place I did two things, first was mark the center hole for for the cradle mount bolt, and two, make a few marks along the perimeter of the cradle so I would know it's position. With this done, I drilled the mounting hole, primed it, and painted it to prevent future corrosion. Side-by-side shot of the cradles so you can see where I chose to drill the hole (modified on the left, stock on the right).
Now, this is where marking the perimeter locations of the cradle come in handy. It mounts to the axle via to carriage bolts , but you'll notice that the cradle rests on the heads of the bolts. This requires making some relief cuts in the cradle, but it also has some radial support ribs on the underside. Rotate the cradle until the bolt heads line up with the unsupported perimeter sections of the cradle and mark for the relief cuts. I used a 1” belt sander and files to hog out and shape the material. Once you are done it should look something like this.
With the cradle bolted on you can see how the cradle is offset towards the inboard side.
With this bolted on to the lower axle mount, the rest of the installation can go according to the Air Lift instructions. Everything should look like this when done.
Routing the air lines is personal preference, but I chose to replace the license plate bolts with the air stems. I plumbed the bags separately, and for good reason. If they are plumbed to the same air line using a T-fitting, they will transfer air bag and forth to your detriment. Think of it like this, while cornering, the bag on the outside wheel will be loaded up due to the sway of the vehicle while the inside bag will be unloaded. If connected, air from the outside bag will simply take the path of least resistance and flow to the inside bag, softening the suspension and increasing body roll. If plumbed independently, this cross-over flow doesn't occur and stability will be maintained.
That said, I chose to route both lines down the driver's side frame rail along the existing wiring harness. The passenger side bag line could be routed along the passenger side frame rail, but there were no convenient places to secure it. I instead routed it down onto the axle, ensuring enough extra line to account for axle droop, before running it across to the bag. After staring at it a while, it was, all in all, the cleanest way I found to route the lines.
Instead of drilling additional holes for the valves, I instead ran them up to the license plate and replaced the license plate bolts with the valve stems. This required drilling out the hole in the plastic backer a little bit, but it was a minor inconvenience achieve, what was, in my eyes, the neatest way to do it.
With everything installed, I highly recommend doing an overnight leak down test. Inflate the bags to 100 psi, then let them sit overnight. In the morning, measure the pressure again. According to Air Lift, some pressure loss can be expected, but anything greater than a few psi indicates a leak in the system that should be fixed. Alternatively, after inflating the bags, a mixture of soapy water can be sprayed on the system to suss out any leaks. In my case, the system loses somewhere between 1-2 psi per bag per day.
How does it ride post-bag install? Fantastic! The stiffer rear suspension helped prevent the wallowing we were experiencing and restored the ride quality. No longer would the truck buck when hitting a bump, nor would it porpoise or have excessive sway. Some of this is attributable to the bags alone while some is attributable to the shock upgrade. Either way, after upgrading both I no longer feel the need to add a sway bar to help control the rear suspension.
Now, an important aspect of the discussion is access to an air compressor. On my Tacoma, I had an ARB CKMA12 unit under the hood that was awesome for airing up tires. This same unit would be adequate for inflating air bags, but the duty cycle ruled it out for inflating the tires to 80 psi on the Ram. ARB offers a twin chamber, 100% duty cycle compressor that I intended to install but ran out of time. Initially, I had a mountain bike shock pump that I was going to use, but that idea quickly went out the window as soon as I realized it would take 3 pumps to put 1 psi in the bag. It only took one session with that shock pump netting 60 psi before I abandoned that idea and bought a cheap 12V compressor at Harbor Freight. While it constantly sounds like it's going to self-destruct while running, it keeps ticking and so far has not let me down.
Driver's Bag Pressure: 78 psi
Passenger Bag Pressure: 78 psi
On 8.6.18, while traveling through Fortine, MT, we got a flat tire. No fault of our own, just so happened to pick up a screw on the road way that put a hole in my driver's side rear tire. Unable to easily get to the spare, I ended up plugging the tire and relying upon the Harbor Freight air compressor to get it back up to pressure. It did it, albeit rather slowly, but it did it. Probably took the better part of 10 minutes, so the compressor would probably trigger the thermal switch and shut down if you had to do more than 1 tire, but I'm glad I had it along.
Links to Products Discussed in this Post
Air Lift Ultimate bags: https://www.amazon.com/gp/product/B00B32DISA/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1
Daystar cradles: https://www.amazon.com/gp/product/B0084ROJBM/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
Harbor Freight air compressor: https://www.harborfreight.com/12Volt-150-PSI-Compact-Air-Compressor-69285.html