Fun With Air Ride, Part 1

“Air is a mixture of gases – 78% nitrogen and 21% oxygen – with traces of water vapor, carbon dioxide, argon, and various other components. Air is usually modeled as a uniform (no variation or fluctuation) gas with properties averaged from the individual components.”

Ok, so this is simple enough, right?  Air simply floats around us all day, we breathe it in with rarely any consideration over whether we have enough, whether it is properly filtered, whether we will be able to expel the unwanted water vapor…really, on a daily basis, the average person hardly gives a second thought to the air around him.

If my mother was still living, my Blog might have as many as three readers.  I may have as many as two readers simply because I’m married.  So this won’t be front-page news in the morning (or ever, really).  But it’s relevant here, so I’m going to go ahead and put it out there…I have a roller coaster-like combination of a high IQ and Obsessive-Compulsive Disorder.  I’ll pause here in order to allow the reader to adjust to this earth-shattering revelation.

In our cars, air is just as vital as it is to our bodies.  Every car has some sort of air filtration device, designed to ensure that the air our engines breathe is clean and free of particulate matter.  But really, it still doesn’t warrant much thought – unless something goes wrong.

But, when nothing is wrong, and the air filter is still well within its usable life, when all of your hoses and other various parts are in good repair, and there is no danger of a vacuum leak, there is still room for one to obsess over the air used by his vehicle… Especially if that vehicle rides on a cushion of air.

Air ride (also known as an air suspension system) is nothing new, and I won’t bore you with a history lesson…

But I will invite you to take a short mental journey with me, so that you can understand what I’ve been through.  It is relevant here, and this is my story, so…

This exercise requires certain assumptions, so:

  1. Let’s assume that you have an IQ on the order of Einstein’s 160, and;
  2. You have a great deal of automotive suspension knowledge, and;
  3. Your knowledge of suspension systems is more from an engineering standpoint than that of a mechanic, and;
  4. You feel that a vehicle, any vehicle, is characterized most by its suspension, and;
  5. You have a thorough knowledge and understanding of the principles of suspension design, and;
  6. You own high-end 3D Modeling Software and enjoy using it at a high level, and;
  7. You obsess over every detail, plan and explore the ramifications of every adjustment, and scrutinize every potential modification, however small, and it effects on every other facet of the suspension system and the car to which it is attached, and;
  8. You have to collaborate with other human beings, who, passionate as they may also be about suspension systems, do not have the same education or approach that you have, and;
  9. Consider that the approach that others take, and the skills and experience they bring to the table, are formidable and significant, and that they are experts, and;
  10. You have goals for your suspension system that go far beyond simply laying the vehicle out for show, and;
  11. Let’s further assume that it would be a mistake to spend more than the car is worth to upgrade the car, even if your budget would otherwise allow it.  So this limits the modifications that are feasible (even though there are no limits to what is possible, especially with your superior intellect).

If you can imagine all of this, then you can understand the obsession.  The compulsion is what drives one to continually pursue a project, at great length, as long as it takes, until the project is complete.  It is not a desire – desire is not strong enough.  Desire does not keep you up till all hours of the night, working on “one little thing” for just “one more minute.”  If you routinely wake up disoriented, in front of your computer or elbows deep in your project, every light in the room on, with the sun flooding in through the window and your wife wondering, “What happened to you last night?” you might have a compulsion.

My air ride obsession/compulsion started with a simple question – “Can I build a better suspension system than the manufacturer, with their astronomical budgets, throngs of scientists, engineers and experts and hundreds of years of collective experience, was able to build?”  And anybody with any common sense knows that the answer is “No.”  And, of course, if I had any humility at all, this story would end now.

The first step was to define the characteristics of a “better” suspension.  My criteria were pretty simple – I wanted a more comfortable ride, with better road holding, improved traction, improved bite on turn-in, less understeer, better lateral acceleration and less body pitch and roll in both cornering and braking.  I was not willing to sacrifice drivability, acceleration or braking performance, or suffer excessive tire wear in the process.  Once installed and adjusted, excessive maintenance demands were also out of the question, and durability was expected.  This should be easy, right?

Once I had given this problem even this small amount of thought, I could simply not tear myself away.  Compulsion required that I see it through, and so I began.  The Subject Vehicle was a first generation Cadillac CTS, GM Chassis Code Sigma.  The base model came factory-equipped with a front suspension consisting of unequal length upper and lower control arms, a modified McPherson strut, coil spring and anti roll bar.  The rear was a fairly standard independent setup with unequal length upper and lower control arms, coil springs, tube shocks and anti roll bar.  In factory trim, the lateral acceleration measured .83 g on the skidpad.  It’s a rear drive platform with characteristic understeer.  The GM Suspension Code was FE1, also referred to as “Soft Ride.”

Honestly, a normal person might have achieved some of the performance improvements that I sought simply by replacing the tires with a more aggressive set.  And new tires are on my list as well.  But, of course, my plan was slightly more complicated than that, as you will all see in Part 2…

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