Air Suspension - How to Choose and Install

[Michael Forte]

What I enjoy most about old cars is that they can be restored to original condition, radically customized, or somewhere between those extremes, reflecting the owner's individual style.  For my '63 Convertible, I want to achieve a mostly original look, with minor custom touches to make it clean, smooth, and low.  This article is to share my experience in choosing and installing the suspension components to achieve a low stance and a comfortable ride.

I purchased my car in August of 2015 and being a hot rodder to the core, I planned to lower it before I even wrote the check.  Once I got it home, I researched and planned for over a year about all the changes I was going to make and the order in which I would do so.  The picture below is pretty much what the car looked like when I bought it.  The previous owner added a stereo, dual exhaust, and 22" wheels, but everything else was original.  

Photo 1: Before suspension modifications

If I simply wanted a lowered car, I could have cut a turn or two out of the original coil springs and called it a day.  But that method hurts the ride quality and can make it difficult to navigate the horrible uneven roads we have here in Northern California, not to mention speed bumps and driveways.  I chose to install an air suspension for both ride quality and adjustability.

The basic parts of an air suspension system are air springs (known as air 'bags' or 'bellows'), air lines and fittings, air tank and compressor, air solenoid valves, and some type of control system to actuate the valves to fill and empty the air springs to raise and lower the car.  Figure 1 illustrates this:

Figure 1: Basic Air Suspension Diagram (from www.buyautoparts.com)

Before any significant purchase, I always determine what's available and research the products quality, reputation, features, etc.  I found that if I wanted to install air springs in a '63 Cadillac, there was a choice of either adding an air spring mounting bracket to the original control arms or buy new control arms with the mounting provisions already included.  Because my control arms were original and in need of new bushings and ball joints, I chose to go with new tubular steel front and rear control arms that include all new bushings and ball joints as well as an improved geometry to prevent the binding that can occur when original control arms are used.  As far as I know, there's only one company offering such products - CB Chassis Products from Fresno, CA.  Formerly known as Choppin' Block, CB Chassis is well known for quality aftermarket Chevrolet C10 truck suspension parts.  Their front and rear suspension kits for Cadillac have air spring mounting provisions built in, so the only modification you have to make to the car is to trim the front spring pockets in the frame to allow for the air spring to clear the opening.  Figures 2 and 3 are renderings of the suspension components included in the CB Chassis kit including the upper and lower control arms, spring mounting cups, shocks, and front shock relocation brackets:

Figure 2:  The CB Chassis Products front suspension kit components, left side (from www.cbpro.com)

Figure 3: The CB Chassis Products rear suspension components (from www.cbpro.com)

Once I had the parts and devised a plan of attack, I raised up the car and removed the front and rear suspension.  The rear housing has two stamped steel lower control arms (shown attached to the rear housing in Photo 2 below) and a stamped upper yoke shown in both Photos 2 and 3.  These will be replaced with new components from the suspension kit.

Photo 2: Rear axle housing removed

Photo 3: The upper control "yoke" removed from the car

With the rear disassembled, I removed all the front suspension components including upper and lower control arms, strut rods, shocks, and coil springs.

Photo 4:  Front frame rail after suspension was removed

With the old suspension removed, I took some time to clean up years of caked-on grease and grime from the area.  After a good cleaning, I started re-assembly. 

Photo 5: Rear axle housing after a thorough cleaning, fresh gear oil, and some new paint

I installed the cleaned-up rear housing first.  Photo 6 shows the new tubular lower control arms with lower spring mounts, the Dominator D2600 air springs, and KYB shocks.  The lower control arms are adjustable to allow for rear alignment and pinion angle adjustment. If you look closely just ahead of the air spring, you can see the ride height sensor which is part of the AccuAir e-Level control system.  A better view of the sensor is shown in Photo 7.

Photo 6: The rear axle housing installed

Photo 7: AccuAir e-Level ride height sensor.  There are four of these - 1 on each corner.

Working on an 18' car in a 20' garage has its challenges, but I've built 3 cars in here so I'm used to it.  I'm hoping Santa will bring me a Rotary lift one of these years.

Photo 8: A bigger garage would be nice...

The next step is the front suspension installation.  As mentioned, the upper spring pockets in the frame need to be clearanced so that the air springs don't rub.  An air springs worst enemy is friction which will eventually cause a rupture.  Unmodified, the spring pocket is too small for the spring.  Using a cutoff wheel, I had to cut out about 1/2" from the outer edge of the pocket to achieve 1/2" clearance to the spring.  Photo 9 shows the driver side lower control arm with the lower spring mount built-in.  The CB Chassis design eliminates the rubber bushing at the front #1 crossmember end of the strut rod and instead uses a spherical rod end (known as a heim joint - see also Photo 10).  The design also replaces the bushing on the #2 crossmember-end of the lower control arm with a large spherical joint.  These changes allow for free range of movement throughout the suspension travel.

Photo 9: Front lower control arm with adjustable spherical rod ends

A bracket attaches to the front #1 crossmember where the factory strut rod and its rubber bushings would attach.  The new lower control arm rod end bolts to the bracket (see photo 10).  The hole in the foreground is the new location for the front shock absorber.

Photo 10:  Front suspension radiator core support attachment location

Photo 11: The completed front suspension as viewed from the front crossmember

After installing all the components, I put the wheels back on and put the car on the ground to see whether the hard work paid off (Photo 12).  I didn't take any progress photos of the air supply system, but I need to mention the air lines and fittings that go along with the air springs.  I routed the lines to the area under the convertible top well where the AccuAir solenoid valve block will be mounted.  The air tanks and compressors will be nearby in the rear quarters of the trunk.

Photo 12: As low as it goes

An important element of the air suspension system is the air supply.  There are options as far as compressor and tank size but 3 and 5 gallon tanks are common.  Considering the plan I had for the trunk interior finish, I chose to use two 3-gallon tanks and two 200psi compressors, one on the left and one on the right.  (Right side shown in photo 13).  The tanks and compressors will later be hidden by upholstered panels.  The ride height controller and solenoid valve assembly is located under the convertible top well, also hidden from view.

Photo 13: Right side 3-gallon aluminum air tank and Viair 444C compressor.

Different manufacturers market and offer various ride height controllers and finding one that suits your needs can be challenging.  In the end, I like the high quality and simple user interface of the AccuAir e-Level air management system.  It uses four air valves (one per corner), four ride height sensors, a tank pressure sensor, and a simple touch pad interface.  While most of those components are hidden, the touch pad needs to be accessible to make height adjustments.  With a little modification (photo 14), I mounted mine in the driver side ash tray which allows it to be stowed but easily accessible when I need it.

Photo 14: Test fitting the e-Level touchpad in the modified ash tray

The e-Level touch pad allows you to control each air spring individually (up or down), or you can choose from one of 3 programmable preset height positions - 3 is 90% height, 2 is ride height, 1 is 10% height.  In addition, there's the full down position which is, well, laying frame.

Photo 15:  The e-Level touchpad finished installation

With the job complete, I celebrated by attending several car shows this summer, putting a few hundred miles on in the process.  

Photo 16: The end result - in the weeds as they say - at the Goodguys West Coast Nationals 2017

It would be difficult to estimate the amount of hours I spent on the installation since I did so while doing a bunch of interior work (the subject of a future article) at the same time.  If pressed, I would guess it took about four solid days to do the job, not including the ash-tray modification and rear axle housing cleanup.  

I get a lot of questions about wheel size and backspacing so here's an update.  I've since upgraded the wheels to HRBB Amarillo's.  They're 22 x 8.5 with 5.5" backspacing.  Tires are 255/30-ZR22 Michelin Pilot Sport.  I've also upgraded to 6-piston Wilwood brakes with 15" rotors in front and 4 piston Wilwoods and 14" rotors in the rear.  

Photo 17: 2019 update - At the Park Street Car Show in Alameda, CA.  

I hope you found this article informative.  Thanks for reading.

[Michael Forte]

Hi Mack, Dominator D2500 in front, D2600 in rear.

Manuel, my car has no sway issues at all, even without the sway bar.  Even at 70MPH freeway speeds it handles well.  If your two front bags are sharing the same air, I suspect that's the problem.  If you don't have the bags separated and they are sharing an air line, one bag in compression will force air into the other side and raise it - exactly what you don't want.  You have to have 4 corner valves.

[Michael Forte]

Thanks so much Tony for the kind words about the article and my car.  It's definitely the nicest car I've owned.  And while plenty of cars came and went over the years, this one is a keeper!

Happy motoring!

[Michael Forte]

Manuel, that piece that looks like an upper bag cup is just a bag spacer.  It fits up into the spring pocket but some of the bag still goes into the pocket as well, so unfortunately some trimming will be needed.  The CB kit is really nice - high quality stuff.  I’ve had mine for several years now and no complaints.

Tony, you are correct.  Most GM cars of that era had the same switch operation. My ‘66 C10 even had an additional position, one click further counter-clockwise, named the “lock” position.  It didn’t seem to add much value though since you could easily reach under the dash and jumper the ignition with a paper clip.  Lol

[Michael Forte]

Hi Manuel, the upper mount doesn’t eliminate the need to clearance the factory spring pocket. You’ll still have to cut some away.  Good luck with yours!  It’s a fun mod that looks and drives great. 

[Michael Forte]

Hi Bob, I’m not running a front sway bar.  I haven’t really noticed that I need it, so I haven’t really thought about how to attach one.  The cbfab control arms don’t have mounting provisions to attach the sway bar links.

[Michael Forte]

Not that I know of.  All the ones I’ve seen have the shock relocated toward the front or rear of the spring.  

[Michael Forte]

Ian, there are shocks in front.  They're just relocated and don't go through the center of the spring (although ridetech makes an airspring with a shock going through it called shockwave).  Air springs act just like coils - the car would bounce like a buggy without shocks.  In my blog post, check out the rendering in figure 2.  The shocks are relocated in front of the control arms.

[Michael Forte]

Ian and Matt, thanks for the compliments.  I'm more than happy with the ride quality.  This was my first air suspension so I was skeptical and hesitant. The goal with this car was to lower it and keep it comfortable.  Only air suspension can do both.  

Of course it's more firm than the worn out suspension I removed.  I could make it more "squishy" like it used to be just by changing the shocks, but it's comfortable and enjoyable to drive it anywhere just as it is.

[Michael Forte]

Thanks all for the feedback!

[Jason Edge]

Added to Help Page.