Mod: Rear Air Springs
DETAILS: Rear Air Springs
I’ve been very happy with my Fox Shocks and Hellwig Sway Bar, but I wanted to assist my leaf springs to help carry the heavy load of the RV. I looked into a leaf spring assist kit or even adding a leaf, but the most compelling and versatile solution was the addition of rear air springs (also known as airbags, air assist or semi-air suspension).
Air springs are installed where the factory bumps normally live (same place Sumo Springs are installed). They lift the suspension up with air, reducing the weight on the leaf springs. As a result, they recover the lost motion from the RV’s weight-induced sag and help stabilize the chassis due to the additional support. Recovering this lost suspension range allows the suspension (both the leaf springs and the shocks) to function with the intended up/down travel.
Additional benefits include:
Increased clearance / prevents bottoming out
Safer load carrying
Level loads independently side to side
Fully adjustable even when in motion
Adjustable for varying configurations (i.e. when towing, not towing, etc.)
Reduce suspension fatigue by increasing suspension travel
Stabilize body roll / smoother overall ride
Quieter ride and less noise/rattles in the house
Inflating while parked raises rear end and makes house more steady
Summary of Use and Experience
I’ve been driving with the air springs installed for over 1,800 miles on various road types in three states and I’m very impressed! Since the air springs are fully adjustable from the driver’s seat, I’ve experimented running them at min/max air pressure extremes — and everywhere in-between. With minimum air pressure, you won’t even know they are there — and fortunately the air springs have an internal bump stop so you’re always protected. With maximum air pressure, you’ll get an approximate 1.5” lift giving you roughly 2.5” of additional clearance at the rear (but it will be a stiffer ride like Sumo Springs).
I’ve found the sweet spot at a low to medium pressure (2-4 bars) for a smooth ride while eliminating leaf spring sag (more on “bars” below). However, when entering/exiting a tricky driveway like some gas stations, I air up to 6+ bars for extra clearance to avoid bottoming out. As I drive away, I simply air back down to my desired level while in motion — amazingly easy!
My rig is naturally heavier on the passenger side and it tends to always lean that direction (the fridge, batteries, generator, fresh water tank, water heater tank, awning, bed and underbed storage are all on the passenger side in my 2018J). As a result, I run more air in the right air spring than the left to level the load side to side. You can also air up the right spring when parked on a crowned road to lessen the lean. The instructions say it’s not uncommon to have a 3 bar difference side-to-side to balance the load in an RV.
Another useful situation to add extra inflation to the air springs is when backing up over a high curb and you need clearance for your levelers. You can increase the clearance by 2” temporarily to clear the obstacle.
What is a “bar” of pressure?
A “bar” is a measurement of pressure in Europe and other places that use the metric system: 1 bar is equivalent to 14.5 psi (or 15 psi to round up). The air springs in this kit should be inflated to a minimum of 1 bar (15 psi) and a maximum of 7 bars (100 psi) while driving. They can and should be deflated to 0 bars (0 psi) when lifting the rig for maintenance, deploying automatic levelers, etc. Amazingly, despite the 100 psi limit, the air springs’ specs note that they are tested to 750 psi and won’t rupture until 1,000 psi. So, the published operating range of 15-100 psi seems very safe. In fact, the manual states that properly maintained air springs will last indefinitely.
In summary:
0 bar = 0 psi = recommend when lifting the vehicle
1 bar = 15 psi = minimum air pressure (while driving)
7 bar = 100 psi = maximum air pressure
What’s Included?
Everything but the tools! All components including the air springs, brackets, pump, controller, air lines and all fittings come in a single box. You could probably source all of these things separately and build your own system, but this is a one-stop-solution that is designed specifically for the 3500 Sprinter (mine is a 2016 MB chassis).
Installation Overview
It took a friend and me a total of 2 days for the install. It probably could have been done in one long day, but we were methodical about the tidiness of everything. You’ll need basic tools like a large allen wrench set, 19mm socket set and torque wrench. It’s a bolt-on system, so there is no drilling into the chassis.
Please note: if you don’t have automatic levelers, I would not be inclined to install these DIY. My HWH levelers + my bottle jack made the install possible! Without levelers, it would be a very difficult install and I wouldn’t recommend attempting it on your own.
In the sections below, I highlight some specific choices and techniques that are not necessarily covered in the installation manual. As such, this is not a step-by-step guide. It’s critical to read the instructions before you start. I’m mainly covering some unique tips and tricks to augment the detailed instructions that come with the kit.
Also, I’ve included captions with all of the photos. If you click through the photos/captions in order, it will provide a good overview of the install and help make more sense of the details below.
Air Spring Installation
The mounting hardware and air springs are of the highest quality, and the hands-on installation will give you great confidence in the product and its operation. The install process is mostly straight-forward, though a couple steps are a bit tricky and I’ll explain the techniques I used below. The top bracket gets installed where the OEM rubber bump stops used to live (see photos). To make room for the bottom bracket, the metal bump stop needs to be removed via the two torx bolts on each side. Additionally, two changes are required:
First, there is an unused half-moon shaped “latch” that is used as a mounting location for self-leveling headlights (an option we don’t have). It’s only found on the driver’s side and it is in the way of the bottom bracket of the left air spring. It needs to be removed with an angle grinder or hack saw (see photos). It’s daunting at first, but it’s not structural and it doesn’t affect anything negatively in the future, including a reversal of this air spring mod. Treat the cut surface with a protection primer (like Rust-Oleum) to avoid rust.
Second, the extended leaf spring spacers located below the spring pack (and just above the axle) need to be rotated 180 degrees to allow the bottom air spring bracket to lay flat. After rotation, the protruding section (which was the mount for the metal bump stop) will now point toward the wheel instead of the differential — it will make sense when you see it. There is no interference upon rotation, and this is required in order to create the space for the bottom air spring bracket. Again, this change doesn’t affect anything negatively in the future including the ability to reverse this air spring mod.
Per the instructions, lift the vehicle but keep the tires touching the ground (I used my HWH levelers). I used heavy-duty zip ties to hold the spring packs neatly together, though I don’t think this is necessary (see photos). Now, working on one side at a time, loosen the u-bolts but don’t remove them or the nuts so everything stays connected and in alignment. Once the u-bolts are loose, use a jack and a piece of wood (I used the bottle jack that came with my rig) to lift the spring pack from just behind the axle. This will lift the springs just enough to create the needed vertical space to rotate the leaf spring spacer 180 degrees. Once rotated, lower the bottle jack and tighten the 4 u-bolt nuts back to spec (which is 118 ft. lbs. on my 2016 chassis). Nothing moved or shifted and this step was easier than feared.
Next and last step is installing the air spring and bottom bracket which is now very straight-forward since there is space for it to be secured. There is an optional spacer in the kit for the lower bracket that I didn’t end up using on either side (the instructions explain when/why to use it). The bottom air spring bracket on the driver’s side has a new “latch” built-in for the self-leveling headlight sensor option.
Compressor Pump Installation
I installed the air compressor pump and relay in the exterior compartment just behind the driver’s door. It’s located up high, out of the way. It didn’t take up any usable space. I mounted it sideways attached to the aluminum “wall” of that compartment with the self-tapping screws pointed toward the front of the rig. That aluminum is grounded, so I used it for the required ground connection and attached the relay on the same aluminum surface (see photos).
I drilled a hole and used a grommet to feed the power cable, white relay cable and the master air line down through that compartment into the area where the propane fill and regulator is located. Within just a couple feet, these all meet up with the two air lines coming from the air springs. Together, they all continue forward (in split-loom conduit) to enter the firewall and get connected to the gauges/controls accessible from the driver’s seat. More on the routing of the air lines and conduit below.
Dual Air Gauge Controls Installation
It’s a luxury to have the air up/down controls in the cab. It’s also a benefit to control each air spring separately (some systems have a single control for both springs simultaneously). The logical mounting location is low and to the left of the steering wheel (see photos). It mounts easily with the included bolts, washers and nuts (requires drilling two small holes). I added a black spacer to the left side to make the controls more level with the horizon since the mounting location isn’t level to the floor (see last photo).
All of the air lines enter through the firewall from directly behind this location. There is an existing hole where all of my HWH wiring enters, and I reused this same hole/grommet. I resealed it with Permatex Black Rubber Sealant.
When cutting the air lines to length, it’s important to use a specific cutting tool like a PEX tube cutter to ensure a clean, perpendicular cut.
Fuse Box Wiring + Switch Installation
I hard-wired the pump to a hot circuit in the chassis fuse box with a 12 awg add-a-circuit. Instead of using an accessory fuse slot, I opted to make it always hot and added my own 12v in-line rocker switch so I have the option to run the air springs anytime I want (even without the key in the ignition). I mounted the rocker switch on the underside of the control unit of my HWH levelers which is in a convenient position just above the air gauge controls (see photos).
I ran the ground wire from the dual air gauge controls to the chassis ground under the hood (see photos).
Running the Air Lines in Conduit under Chassis
I decided to run 100% of the air lines in black split-loom conduit. The directions only call for protecting any section of the air lines that are near sharp edges, but I wanted to protect every inch of every air line. They can be neatly zip tied to existing bundles of conduit running the same direction underneath along the driver’s side. I used 3 sizes of split-loom conduit based on the contents inside (i.e. a single air line, two air lines, three air lines + two wires). This choice will be obvious during installation.
I ran the right spring air line across the underside of the chassis to meet up with the left spring. Together, both lines then run together in a single conduit to the vicinity of the pump. At that junction, a third air line and two wires join in a larger conduit which is routed all the way into the engine compartment (following the HWH levelers conduit line). They continue to follow the HWH bundle through the firewall and into the cab on the wall behind the brake pedal. At that point, the three air lines and two wires are within inches of the control panel and the chassis fuse box. It’s a good idea to include service loops (or at least some slack) near the air springs and behind the dual air gauge controls.
Setting Air Pressures
Since every vehicle is different, there is no “ideal” air pressure. However, it’s recommended to start with 2.5 bars on both air springs and adjust from there. I did a lot of vertical measuring (from the ground to the top of the rear wheel wells as well as the hitch), and determined that 2 bars on the driver’s side and 4 bars on the passenger’s side is a sweet spot for my specific rig. The extra air on the right is offsetting the tendency for my rig to lean to that side due to weight. A difference of up to 3 bars side to side is considered common for RVs (according to the manual).
Dimmable Light
What mod is complete without a lighting component? I installed a small, dimmable LED light strip that illuminates the dual air gauges so I can see the air pressure in the dark. I used the bottom of my HWH control panel as the location since it was perfectly located just above the air gauges (same location where I located the master pump switch noted above). The last three photos/captions show this in detail.
How to Purchase
The kit is assembled and shipped from a company named Drive-Rite, located in Dublin, Ireland. Yes, it’s an international company. They were easy to work with, took my order over the phone, it shipped the next day and I received the product less than 48 hours after it shipped! I paid for international priority shipping, which was expensive, but if you don’t mind slower shipping, there are certainly cheaper methods to ship (just tell them when you need it).
Email Austin McGowan at Austin.McGowan@amk-group.com or call him at +353 18612 632. I used Skype to make a cheap international phone call. I’m not affiliated with him or his company, but if you mention the guy from the “View/Navion website” I’m sure he can look up my order.
Pricing
As of July 2023, the complete kit was approximately $1,000 USD + $250 for International Priority air shipping with arrived in 2 days (you can opt for a cheaper/slower shipping option). Additionally, I was billed a $32 customs charge by FedEx which cleared and paid customs upon arrival in the USA. Altogether, it was under $1,300 total which I felt was pretty reasonable for the exceptional quality and versatility of the system. I paid by credit card over the phone.
PARTS AND TOOLS:
Air Spring Suspension Kit: www.driveriteair.com/catalog/search/product/DR.02.014000-181
Compressor & Dual Gauge Kit: www.driveriteair.com/catalog/product/DR.11.016512-391
Add-a-Circuit: www.amazon.com/dp/B083R554LP
PEX Cutters: www.amazon.com/dp/B01KSYTLUW
1/2” Split-loom conduit: www.amazon.com/dp/B0CB864VYM
3/8” Split-loom conduit: www.amazon.com/dp/B07PNBYWMP
1/4” Split-loom conduit: www.amazon.com/dp/B078KNH36V
12v Rocker Switch: www.amazon.com/dp/B07CN2K8MX
12v Dimmer Switch: www.amazon.com/dp/B01C4UBMY6
LED Light Housing: www.amazon.com/dp/B09K7H6XRK
LED Strip: www.amazon.com/dp/B00HSF64JG
Spacers: www.amazon.com/dp/B0B5R5DCV8
Permatex Sealant: www.amazon.com/dp/B000HBM37A
MANUALS:
Air Springs Installation Manual
Pump/Controller Installation Manual
Semi-Air User Manual