Motivemagazine: The Ups and Downs of Coilover Suspensions

[Tycoon]

words: Bryan Joslin




You worked overtime and saved up all your spare change to score your first real performance car, and now it's sitting in your driveway for all the neighbors to see. You can't stop looking at it, but not because it's so beautiful; even with all its power bulges, air intakes, and fat exhaust tips, something is still missing. Then you see it, clear as day. The chassis sits on its wheels like a scared cat waiting to pounce. This thing needs to be lowered!

Some of the most focused performance cars must still bow to the lords of legislation and practicality, resulting in factory suspensions that make them look more ready for two-tracking than road racing. It's no wonder aftermarket suspensions are among the most popular owner modifications today, and chief among them are coilover suspensions.

The term "coilover" is actually a misrepresentation of the main technological feature of these suspensions, which is their adjustable height. In the purest sense, most modern cars are equipped with a coilover-type suspension right from the factory, where a coil spring is mounted concentricallyover a shock absorber or strut assembly. Of course, these almost never allow for ride-height adjustments. Conversely, many aftermarket companies make so-called coilover suspensions for cars that don't even employ a coil-over-shock design in the first place. As Jerry Seinfeld would ask, "What's the deal with that?"

In the Beginning...
Long before there was NOPI TunerVision or Hot Import Nights, there were threaded-body adjustable coilover suspensions. But they weren't on street cars, they were on race cars, and they served a wholly different purpose than lowering the car for street cred. The original raison d'etre for an adjustable coilover assembly was to corner-balance the car for specific track conditions. When minor adjustments are made to the height of the suspension at each corner, weight is gradually transferred to opposite corners - allowing crew chiefs to dial in the perfect chassis balance. Dialing up at the front, for instance, moves more of the weight over the rear axles for better rear wheel traction.

This technology filtered downstream to amateur racers and eventually to street tuners. In 1988, H&R Springs released the first series of street coilovers and a host of other companies followed suit. And while racers still opt for this setup for ideal tuning, the primary focus of adjustable suspensions has switched from corner balancing to optimizing ride height for aesthetic reasons.

The basic construction of most coilovers is the same: The inner part of the assembly consists of a tubular shock absorber or strut body, a portion of which is threaded on the outside. A coil spring sits outboard of the shock, resting on a perch whose location is dictated by how far down the threaded body its lock nut has been dialed. When the springs and shocks are mounted separately, as is the case in some rear suspensions, the spring perch alone will be height-adjustable.

For the typical street setup there is usually a three- to four-inch range of adjustment, and the thread pitch tends to be fairly fine, allowing for very precise alterations. Since street coilovers are generally made for the performance-enthusiast market, most of them offer a significant drop even at their highest setting and go even lower for more dramatic effect.

While coilovers are generally sold as full spring-and-shock kits, some companies offer the option of converting your existing suspension to adjustable hardware. Ground Control, for example, offers conversion kits that include external threads and spring perches. Going this route is much less expensive than buying full height-adjustable suspension components, but will typically require more work to get properly fitted.


The Ups
The advantages of an adjustable suspension are numerous. For those who take their track driving seriously, it offers an easy way to tailor the chassis settings for constantly changing conditions. A few minutes of fine-tuning between lapping sessions can not only improve lap times, it can also increase tire and brake life. Some setups even offer interchangeable springs of different compression rates for further refinement.

For show-car owners, an adjustable suspension allows the ride to be set at a reasonable height for street driving and then slammed to the ground for display purposes. Not only that, but the machined surfaces look way cooler than plain-Jane shocks and springs when a trophy is on the line.

As for the regular-Joe performance enthusiast, adjustable coilovers deliver a way to truly personalize the car's stance. Not only can the car be lowered, but its rake can also be set for added drama. When the weather goes bad, the suspension can be raised to a higher setting for closer-to-stock ground clearance. And perhaps one of the most overlooked advantages is that the springs and shocks are a matched set for each other, taking some of the guesswork out of matching components from different sources.

The Downs
All is not rosy in Coilover Land, however, so proceed with caution. The most obvious drawback to adjustable coilover suspensions is their cost. Typically in the $1200-2000 range for a complete set, they can run nearly twice as much as fixed sport springs and upgraded shocks. It's easy to see why non-adjustable conversion kits for less than $500 are such an attractive alternative.

Although adjustable suspensions feature a range of settings by design, the range may not be as broad as you might hope. Owners often cite the ability to raise their cars in the winter months and slam them in the summer as justification for paying extra for coilovers, only to discover that the highest setting is still too low to clear an average snowfall and the lowest setting has them introducing their oil pans to manhole covers. Check the lowering range and carefully consider the implications before selecting your suspension.

While their adjustability may be the main reason to select a coilover setup, most people typically choose a setting and leave it. That's because the actual adjustment procedure can be time-consuming and tedious. With a thread pitch of 16, it takes 16 full turns to move the suspension just one inch. With brake lines and fender liners in the way, you may only have a 90-degree window in which to turn the adjusting wrench, that would mean 64 wrench movements at each corner to drop the car an inch. That's 256 opportunities to bust a knuckle.

Failing to adjust the settings every once in a while can lead to damaged or corroded threads. Some coilovers have shock or strut bodies made of regular steel, which will rust if not protected and lubricated. Others are made of stainless steel or aluminum, which won't rust, but will certainly accumulate road debris in the threads. Your best bet is to use a penetrating lubricant and a fine brush periodically to keep the threads clean between adjustments. And don't forget to always clean your threads before making any adjustments to avoid damaging them.

Coilover suspensions are as popular as ever, and with more companies entering the market they are not likely to lose fans anytime soon. The ability to truly personalize the aesthetics and handling of your car is a major selling point. Depending on your priorities and budget, there may be a set in your future.

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[donau]

They sure beat torsion bars. The cost is actually not all that bad relatively speaking. Mine were less than $3,400 for a set of full RSR's fully installed and corner balanced.