Bret Voelkel of Air Ride Technologies
Air springs are to suspension systems what vacuum-secondary carbs are to engines. Catch a glimpse of vacuum-secondaries under the hood of a hot rod and you'll automatically assume the motor's a turd. Real men want full throttle right now, baby, and dig carbs that hit hard! Never mind the fact that vacuum-secondary carbs can easily make as much peak horsepower as their similarly sized mechanical-secondary counterparts without sacrificing streetability. Likewise, witnessing a car that can alter its ride height at will elicits a similar knee-jerk response. Air suspension is for poseurs, not racers, so it has no place in your musclecar, right? Not if Air Ride Technologies has a say in the matter.
The company has developed a habit of making converts out of skeptics. Not just any skeptics, but pros who happen to be among the best road racers in the country. Air Ride enlists big-time racers such as Boris Said and Scott Pruett-two guys who race alongside the likes of Jeff Gordon and Tony Stewart-to test its products, and the feedback from the harshest critics around has been overwhelmingly positive. Common sense says that if it impresses them, it will probably impress you too. So how does it work, what are its benefits, how do you tune them, and how hard are they to install? We talked with Bret Voelkel to find out, and we quizzed him on other assorted suspension design topics as well.
Although it takes the better part of a weekend, installing an air suspension is rather straight-forward. The only special tools you may need are an electric saw and a welder, and a digital angle finder will assist in setting up the pinion angle. "As with any customization, take your time by measuring three times and cutting once," Bret explains. "If you run into a problem or a question, please give us a call, since that is why you bought the stuff from us in the first place. I always advise customers to call a potential manufacturer with some trial questions before buying to determine the level of service they can expect after the sale. We have our installation instructions on our Web site so the customer can get a good idea of what he is in for before buying."
Whether a progressive-rate spring or a linear-rate spring is better for hard-core cornering is much debated, but there is a time and place for each. According to Bret, the only argument against using a progressive spring rate would come from the potential tuning headaches it creates for novices. "A progressive spring rate is just one more tuning variable to throw into the mix when it comes to overall suspension tuning, but if you have an adjustable suspension and the know-how, then that variable is easily manageable," he explains. When it comes to air springs, they can be made to be perfectly linear or extremely progressive. Air Ride typically uses double-convoluted air springs in the front suspension since it's highly leveraged. "This is because the front wheel always travels faster and longer than the air spring and shock, so we want the air spring to gain spring rate much quicker to properly control the oscillations of the vehicle. In the rear, we typically use a sleeve-style air spring with a nearly linear spring rate. Since the rear air spring is more of a direct load application that moves at the same rate as the axle and wheels, it needs more travel and a softer spring rate throughout its travel."
For those with eclectic tastes, an unfortunate byproduct of a tight chassis that handles well is compromised grip at the dragstrip. With the extreme adjustability of an air suspension, however, you can have the best of both worlds. "Just like any other form of racing, setting up an air-suspended car for drag racing isn't much different from setting up a traditional suspension," says Bret. "I am not a drag racing expert, but in general, we try to set the car up as loose as possible without getting into wheelhop. Loosen the extension valving on the rear to allow the rear suspension to lift the car and plant its tires. Also, loosen the front extension valving to allow the front end to come up and transfer the weight to the rear while keeping in mind that some cars like a bit more preload in the right rear spring to plant that tire better."
Air Ride's AirBar rear suspension system converts a factory leaf-spring suspension into a four-link. This begs the question: How is a four-link superior to conventional leaf springs? "A leaf spring is asked to perform several functions in the suspension," explains Bret. "In addition to holding the car up, it is expected to control the lateral, front-to-back, and pinion-angle movements of the rear axle. Obviously, trying to optimize all these functions ends in compromise. By separating the job of suspending the car from the job of holding the axle in the car, we can optimize each job more easily."
"One of the biggest benefits of an air suspension system is the ability to quickly tune the chassis to prevailing track conditions," says Bret. "Theoretically, you could achieve the same performance from a mechanical spring as you could from an air spring if you had the necessary skill, patience, and equipment to properly tune the suspension. However, road conditions are only one factor to consider in a car that sees both street and track duty. If you change the load in the vehicle with passengers or luggage, you have to start all over with the tuning process. It takes a lot of perseverance to tune a suspension via the traditional method of changing components through trial and error. Therefore, people often end up living with some level of compromise in ride quality or cornering performance. An air spring gives the ability to make tuning changes much quicker and easier at the touch of a button, which often equates to less compromise."
"Air Ride has a total of 28 in-house project cars, and there are two simple reasons for having such an extensive collection," Bret says. "First, I feel the only way to develop a product is to have a car in front of you for an extended period of time. This means no customer-imposed deadlines, cost considerations, or squeamishness about hurting their car. Therefore, you must own the car. Furthermore, the development should not stop when the first system is shipped. We constantly evaluate and refine our products based on our experiences on the road and at the track. Since we are building the car anyway, we also take the opportunity to create installation tech and track-day articles and take photos for ads and various feature articles. It is a time-proven method of development, refinement, and promotion that we have copied from the pioneers of hot rodding and racing. The cars are much more a tool than a toy in these respects. The second reason for having so many cars in-house is that it's a great excuse to feed my personal hot rod habit. I love these cars because, as is the case for many of our customers, I grew up with them."
One of the most common snafus of an air suspension install is air leaks, but fortunately, a few simple tricks can help you avoid them. If the air lines are cut cleanly and squarely, and thread sealer is used on the pipe fittings, leaks are actually quite rare. "To locate a leak, the old-fashioned method of spraying the connections with soapy water works best," explains Bret. More likely than not, the culprit will be at one of the connections. "I don't think I have ever seen an air spring itself leak. It's always a fitting that is left loose or has no sealer. DOT-approved fittings are a must as well, since they have a built-in insert that supports the inside of the plastic tubing to seal it better than standard fittings."
The straight-line machines of the musclecar era had some shortcomings in basic suspension design, and Air Ride works hard to correct these issues using modern technology. Bret says most OEM front suspension systems, especially those in GM vehicles, were designed to tilt the top of the tire outward when compressed. This resulted in understeer when driven to the extreme. "Their thinking was that in a panic situation, most drivers would instinctively go for the brakes, which, in a pushing situation would be the safe and correct action, but this design does not offer optimal handling," explains Bret. "Ideally, the top of the tire should tilt inward when compressed to maintain maximum tire contact when cornering, and we offer a taller spindle for several applications that improves this geometry. Likewise, the large, cushy pivot bushings commonly used in the '60s lead to lots of suspension slop. We use a firmer rubber or polyurethane bushing to maintain suspension integrity."
Let's says you've taken the plunge on an air suspension and plan on taking your car to the track. Sure, it's almost infinitely adjustable, but how exactly do you tune the chassis to suit your driving style? "An air suspension is tuned just like any other suspension," explains Bret. "If the front pushes out first, you may have to soften the spring rate or shocks to get the car to take a set and bite. If the rear kicks out first, you may have to soften up the rear a bit to get it to roll over and bite. However, there are many variables in addition to spring rate and shock settings-such as tire pressure, alignment, and sway bar settings-and it simply takes time to figure out how to adjust each to optimize handling."
Construction & Durability
Those unfamiliar with air springs may question their durability, but they're actually the spring of choice in applications far more demanding than any standard passenger car. "Since air suspension is somewhat new to the hot rod world, it is assumed that it is a new invention altogether," says Bret. "The truth is that more than 95 percent of all semitrucks use air springs-and have for over 25 years. Just like a tire, air springs are made from layers of fabric and rubber, and the weave of the fabric is a key element in determining the expansion characteristics and performance of the spring. Firestone's been making air springs for more than 70 years, and they manufacture springs for us to our specifications."
"An air suspension is viewed as being more complex than a mechanical suspension, but in reality, the only additional part is the compressor system," says Bret. "The coil spring is replaced by an air spring, and you still need a shock absorber, just like in a traditional suspension. A compressor system can be as simple or as complex as the customer desires. A simple compressor system would consist of a compressor, a tank, air lines, and an inflate/deflate valve for each air spring. An automatic leveling system would add ride-height sensors and some sort of electronic controls to process the data generated by the leveling sensors. This is an area that has a lot of variables and could fill an entire article by itself."
One of the few drawbacks of air suspension systems has been the different plumbing and electrical connections necessary during installation. Consequently, a typical installation takes 10-15 hours, but Air Ride's new AirPod cuts that time down to 1-3 hours. The AirPod is essentially a combination of compressors, air lines, solenoids, electrical wires, and an air tank that have been integrated into a single assembly. "Since the AirPod comes prewired, preplumbed, and pretested, all the customer has to do is bolt it in with four bolts, plug in four air lines, and connect the power and ground," says Bret. "In comparison, a standard system requires making 17 plumbing connections. With compact dimensions of 20x12x9.5 inches, we made sure it will easily fit in the front of the trunk in nearly any car."