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2003 Volkswagen GTI - Air-Ride Suspension: Project Silverstone

Bags Aren't Just For Groceries; We Install And Test Airbags On Our Mk4 VW GTI.

Jun 1, 2010

What started in the lowrider and hot rod communities has gone Euro. Air-ride is attractive to VW/Audi owners because it achieves an extremely low stance at the touch of a button. Not just for looks, air-ride also has a practical advantage. It's useful for daily drivers in avoiding obstacles such as speed bumps or steep driveways.

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With its growing interest, we ran an Editor's Letter in et 1/10 regarding the hot topic and were bombarded by emails both praising and protesting air suspension. For many, the ultimate stance along with the practicality of air-ride was justifiable, while many purists hated the idea.

Since et had no prior experience with air-ride, we decided to uncover today's air suspension technology by actually installing Air Lift's latest kit on our '03 VW GTI 1.8T project car.

Air Ride 101 Air suspension is really simple. Instead of metal coil springs to support the car, it uses rubber bags full of air. These air springs (aka bags) are made of strong, flexible rubber. The air needs to be at a high pressure to support the car, so its generated by a compressor and stored in a tank until needed. The compressor is compact enough to fit in your trunk. And the air is transferred to the bags through tubes controlled by solenoid valves. An onboard computer controls the valves by either dumping the air or allowing the bags to be filled. The amount of air pressure in the bag determines the height of each bag. The system can then control each bag individually to raise or lower a specific corner, two together, or all four.

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Why air lift? After being happily married to H&R coilovers for six years, it was tough to say goodbye. We certainly weren't unhappy, since the H&Rs had performed well for tens of thousands of miles. But we were curious about the myths of air-ride, so looked for a manufacturer with a history of quality products and good service.

After some research, we discovered the Air Lift company. It's been around more than 50 years, having introduced the original rubber air spring inserts in 1950. What's more, its products were used in stock car racing for 20 years. In the '60s, they introduced sleeve-type air springs for trucks, followed by air helper springs in the '80s for RVs and ambulances. But it wasn't until the '90s that the company tackled the lowrider and street rod communities, developing universal and vehicle-specific airbag kits. There's no other North American air suspension manufacturer with more experience than Air Lift, so we were happy to entrust Project Silverstone to them.

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VW-Specific Parts Since the VW/Audi air-ride scene is still emerging, Air Lift is in the process of developing applications for as many Euros as possible. VW-specific kits are available for the Mk2 thru Mk5, with more applications under development.

Our Mk4 application is considered Air Lift's "performance kit" and features spring (bag) rates tuned for more aggressive driving specific to the vehicle's weight and geometry.

The front uses a strut body with tapered sleeve bags. The strut's damping is nine-way adjustable with a knob located on the front of the strut.

Unique to Air Lift's Mk4 application is the front upper strut mount. Unlike any other air-ride manufacturer, this mount decreases damper rod noise and vibrations in the front suspension. There's also an integrated bumper in the bottom to protect the strut.

The Mk4's rear torsion beam separates the spring and shock, so while the coils are swapped for tapered sleeve airbags, aftermarket shocks can be used (stock units aren't recommended). We simply retained our H&R rear dampers.

Both front and rear bags are cylindrical and comprise a progressive-rate piston in the bottom, allowing it to act like a coil spring. Air Lift's design means they're relatively stiff, and more air pressure typically means a higher spring rate. But by enlarging the internal piston and changing its angle, engineers have been able to achieve a good spring rate at low ride heights.

For the air management, Air Lift provides a five-gallon eight-port tank and a single Viair 380C compressor. There are also push-to-connect fittings and 60ft of 3/8'' flexible thermoplastic tubing in the kit. Two manifolds with adjustable solenoid valves are included as well.

To control the suspension, the AutoPilot is a digital controller connected by a CAT-5 cable. The display shows both tank and individual airbag pressure. Each bag has its own buttons, so can be manipulated up or down. There are also three pre-set buttons for ease of use - all down, all up and a preferred driving height.

One of the benefits of the Mk4 kit is the bags are unlikely to leak. As long as the kit is installed properly, leaks are almost non-existent, even if the car's parked for several weeks. Also, the distance between the tires and bags is at least 0.5'' so are unlikely to foul.

The complete Air Lift Mk4 kit retails at $2600, although are offering it for distributors and retailers between $1900-2200. Components are also sold separately.

How-To We were very fortunate to have Jesse Jenson from Air Lift help us with the install. And thanks to the great guys at DC Performance in Culver City, CA, we had the ideal workshop with a lift and the tools to complete the job.

The install will take a full day but, if you're doing a custom trunk setup or similar, it could take much longer.

Sam's Thoughts Going "air" was one of the last things I thought I'd do on Project Silverstone. I though air-ride was "cheating" but Air Lift's "direct replacement" kit opened my eyes and my mind.

I was particularly anxious about ride quality and performance. Was it going to handle as well as my coilovers? Was it going to be floaty?

Surprisingly, the airbags are stiff. I can tackle the same corners with equal performance. In fact, my coilovers were too low and would often cause rubbing. But with air-ride, I tap a button to raise the car slightly and avoid any rubbing!

For daily driving, the ride is a tad rougher, but it's nothing to complain about. Yet the practicality of air suspension is rewarding. I don't have to approach every driveway or speed bump at a diagonal to avoid scraping the front valance.

As for lowering, I thought it would be lower but the rear sits on the tires when it's all the way down, although the fronts have more to go. Most people modify their subframe and remove the front sway bar to go another inch lower, but I'm happy for now.

I'm also glad maintenance is relatively simple. All I have to do is drain the tank every two months to prevent moisture getting trapped.

Next on the to-do list is fixing the trunk. Jesse installed it quickly but a custom display is in the works. Most people can fit the compressor and manifolds in the spare wheel well, which would give back some cargo space - something I've had to sacrifice for the air-ride. But after driving on it for several weeks, I'm a believer. Don't knock it until you've tried it!

Sam Du
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