Magic Body Control. It sounds like a cheap gimmick, a
feature that gets tacked on to an overpriced mattress. And in a way, it is.
That mattress, it turns out, is a 2015 Mercedes-Benz E-Class, and that Magic
Body Control is an $8000 optional extra.
That's a pricey mattress.
I was puzzled when I came across that line on the options
list, which skyrocketed the mid-level Benz's price to almost 90 grand. The
sales guy, the one whose eyes I could feel rolling at my mere presence,
balanced on his heels and explained the complex system in three words.
"It's air suspension."
That's disappointing.
In my head I had pictured something much more cutting edge,
maybe magnets aimed north to north underneath the car's four corners, keeping
it afloat on an invisible field. Instead, it was just air suspension, the
culprit of saggy old luxury cars past their prime. And in actuality, the idea
of automotive air suspension has been around for quite a while.
Ideas for a pneumatic "cushion" spring for
vehicles were patented as far back as 1901 by a man named William W. Humphreys.
By 1920, George Messier, a manufacturer of pneumatic equipment, had developed
his own aftermarket automotive suspension system. His automotive firm Messier
only existed from 1925 to 1931, but every automobile he produced came with his
air system. Messier's fledgling company, despite being a failure, had opened
the door to "cars without springs."
 |
| Illustration of Humphreys' original patent, a "Pneumatic Spring for Vehicles." |
The Great Depression ground development of the technology to
a halt, but by the mid-1940s, pneumatic suspension systems were being tinkered
with again, this time by the United States military for use in airplanes. Soon enough, it was back to cars--the Stout Scarab, to be exact. A
unique car in its exterior design alone, the Scarab was designed to look like
the beetle of its namesake. But it was a radical car in many other aspects as
well. It was powered by a Ford flathead V8 mounted at the rear, and featured,
you guessed it, four-wheel independent air suspension. Only nine of these
hand-built prototypes were produced, but the Scarab set the ball rolling once
again.
 |
| A 1936 prototype version of the Stout Scarab on display at the High Museum of Art. Only five of these vehicles remain in existence. |
In 1955, Citroen released the DS, a car that would become
one of the most widely recognized French automobiles in history. As you'd imagine, it certainly didn't lack the sort of
zany, oft-illogical flair that Citroen would later become known for. The rear
of the car was narrower than the front, producing a shape unlike any that had
been seen before. Curious, too, was its suspension setup. Technically, the DS
used an oleopneumatic suspension, named so because the shock absorbers were
filled with nitrogen gas and hydraulic fluid rather than air. These shock
absorbers were connected to the sway bars via a piston, which would pump the
liquid and gas filled chamber depending upon the surface. In the DS, you didn't
even need a jack to change a tire. Simply to raise the car up to its furthest
ride height setting (intended to help the driver better traverse rough roads),
place a jack stand underneath, and lower the car via the same dashboard-mounted
switch.
 |
| Basics of the Citroen DS oleopneumatic suspension system. Nitrogen (Gaz) is suspended above hydraulic fluid and activated by a piston connected to the trailing arm. |
It wasn't long before GM caught wind of Citroen's
developments. In 1957, Cadillac introduced the new Eldorado Brougham, which
came standard with an air suspension system designed to maximize ride comfort.
Their system used what would now be considered a rudimentary collection of
sensors that helped the air system compensate for uneven road surfaces. A year
later, and both Buick and American Motors were offering similar systems on
their flagship models. But the early technology was hopelessly complex and the
option for air suspension soon disappeared on all American cars, not to return again until the mid-1980s.
Only European luxury brands Mercedes-Benz and Rolls Royce
introduced air suspension systems throughout the 1960s. Mercedes' system, most
famously the one on the mighty 600 sedan, used hydraulics which also powered
the windows, brakes, and trunk lid, among other components. Meanwhile Rolls
used a self-leveling system licensed from--none other than Citroën--in the 1965 Silver Shadow.
 |
| Nicknamed the "Mercedes Big," the 600 sedan boasted a biblically-complex hydraulic system. |
Air suspension systems may seem complicated next to the
traditional metal coil setup, but in reality, the basics aren't that much
different. The beating heart of every air suspension is the compressor. Most
commonly powered by the engine, the compressor pumps air into the system either
to increase ride height or to level it out--if a heavy load is placed in the
back of the car, for example. Rubber bellows, the name taken from an
accordion-style instrument designed to pump high pressure air into fires, act
as "air shocks" or struts. These rubber chambers sit between the
car's chassis and axles or struts, and are sealed to keep the pressurized air
in.
These suspension systems have a wide array of uses, ranging
from modern buses that "kneel" at the front, providing better access
for disabled passengers, to custom, aftermarket setups, where you can let your
car rest on the (frame) rails while it's parked at a car show.
Ride height adjustability is the biggest advantage in an air
suspension system. In performance-minded vehicles, this allows you to lower the
vehicle, effectively increasing the spring stiffness and improving handling.
Additionally, some systems are programmed to lower the suspension automatically
at high speeds, which improves the car's aerodynamics and road holding.
 |
| Air suspension on the Panamera adjusts at speed, lowering the car slightly for better aerodynamics. |
In off-road vehicles, the opposite is advantageous. The
latest Range Rover, for example, features a system that can raise the vehicle
while stationary, allowing for 11.9 inches of ground clearance. This means that
the Rover can ride at a lower height for around town errand-running, but still
retains its legendary off-road capabilities. However, these systems still
aren't foolproof.
Every now and then, you're likely to see a mid-2000s Range
Rover or Mercedes sitting suspiciously low in a driveway. Failing air
suspension systems are still a huge problem, especially in cars that are
getting a bit long-in-the-tooth. But why do these systems fail? Or, an even
better question, how do they fail?
The most common problem in an air suspension system is
failure of the air shock or strut itself. The rubber bellow mentioned earlier
is subject to the same sort of issues any rubber component faces. Even though
it's shielded in some effect by the wheels and body of the car, it's still
subject to drastic temperature change, which dries out the rubber, eventually
making it brittle, especially around connection points. Even under normal
operation, the shock undergoes small amounts of stretching which, over time,
add up.
Major leaks in any of the air bags can easily lead to
failure of the air compressor. This, because the compressor is working overtime
to maintain pressure in an impossible system. Eventually, the compressor burns up trying to compensate.
More common in custom applications, but not unheard of in
factory systems, is air line failure. In automotive applications, the lines for
air suspension systems are usually the same braided nylon lines used to
transport hydraulic brake fluid. These are very strong, but if the line is run
against a sharp edge of the frame, or placed too close to a moving suspension
component, it's likely to wear out over time and eventually leak.
All of these problems can lead to some very costly
repairs.
A company called Arnott specializes in remanufactured
suspension components for Mercedes-Benz. W220 Benz's--the S-Classes produced
from 1998 to 2005--are experiencing the most issues related to their air
suspension systems, but models as current as the GL-Class, introduced in 2006,
are showing problems. Arnott provides both a replacement air suspension kit
($2700) and a full coil spring conversion kit ($1500). Comparatively, most
Mercedes dealerships will charge up to $600 for a single air spring. And these
prices are all before any labor is involved, although Arnott provides some
excellent YouTube tutorials for their system's installation.
German luxury cars aren't the only ones having problems
though. Second generation Lincoln Navigators, built from 2003 to 2006 on the
Ford Expedition platform, are notorious for having problems with their air
compressor. As mentioned earlier, this is ultimately related to leaky air bags.
Replacement compressors are a fairly cheap piece at around $150, but replacing
them is only putting a bandage on the
underlying problem. At their least expensive, eBay-special prices, replacement
air struts for the Navigator will cost you $300 a piece. By comparison, a
complete set of metal coils and struts costs $400.
Alas, it's back to contemplation mode. For all of the Magic
Body Control's perceived virtues, I'd safely say that, even if given the
opportunity to afford it, I'd leave that box on the options list unchecked. As
for buying a car with air suspension secondhand, my first modification would be
a coil spring conversion.
0 comments:
Post a Comment