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October 14, 2009Suspension components tested:
BMW Original Equipment Springs, Struts/Shocks & Anti-Roll Bars
Eibach Pro-Kit Spring Set (w/ BMW O.E. Struts/Shocks & Anti-Roll Bars)
Eibach Pro-System Plus Kit - Pro-Kit Spring Set, Pro-Damper Set & Eibach Anti-Roll Bars
Eibach Multi-Pro R1 Coil-Over Kit (w/ BMW O.E. Anti-Roll Bars)
2008 BMW E92 328i Coupe
So you're considering installing performance suspension components on your vehicle. Maybe it's to improve the looks by lowering, or maybe you want to improve the handling and responsiveness. Thankfully, a properly engineered performance suspension can do both.
A vehicle's suspension is comprised of many parts designed to work together. The question becomes what suspension components to install - lowering springs, performance dampers, stiffer anti-roll bars or maybe even full coil-overs. The answer depends on your objectives, and how you prioritize characteristics such as appearance, road manners, responsiveness and handling, adjustability, or ease of installation.
Form follows function - the shape of an object should be based on its intended purpose. Performance suspension components follow this simple principal - look better while working better. To that end, the engineers at Eibach design more than just performance lowering springs. Their product range also includes dampers (shocks and struts) tuned specifically for use with their line of performance lowering springs, upgraded anti-roll bars and complete coil-over systems. Each component is engineered to work with your vehicle's suspension, complementing the vehicle's look and performance it delivers.
So, to help answer the question of what performance suspension parts to install, the Tire Rack team conducted a Real World Road Ride and Performance Track Drive using our 2008 BMW E92 328i Coupes to compare various Eibach suspension components with the stock BMW Original Equipment suspension. We evaluated Pro-Kit lowering springs, the Pro-System Plus suspension package (Pro-Kit Springs, Pro-Dampers and Eibach Anti-Roll bars) and the Multi-Pro R1 Coil-Overs (re-using the stock BMW anti-roll bars). All four cars drove on new 225/45R17 Goodyear Eagle F1 Asymmetric Max Performance Summer tires fitted to 17x8.0 wheels. Having the same tire on all four vehicles eliminated a variable from the evaluation, allowing our team to focus on differences between suspension components. The reasonable road manners of the Eagle F1 Asymmetric won't mask or exaggerate the feedback from the suspension components, and also provided enough traction to challenge the suspension upgrades on our test track. Our local mechanic performed the suspension installations, and re-aligned the vehicles prior to our testing.
What We Learned on the Road
Our 6.6-mile loop of expressway, state highway and county roads provides a great variety of road conditions that include city and highway speeds, smooth and coarse concrete, as well as new and patched asphalt. This route allows our team to experience noise comfort, ride quality and everyday handling, just as you would during your drive to school or work.
Installing performance lowering springs with the vehicle's Original Equipment dampers and anti-roll bars is the most common performance suspension installation. So this vehicle was equipped with Eibach Pro-Kit springs, and we re-used the O.E. dampers and anti-roll bars to mirror this common upgrade.
Coming as a pleasant surprise, the car with Pro-Kit springs rode only slightly firmer than the stock suspension, with a taut feel that didn't punish the driver. The Pro-Kit springs did bring a noticeable improvement in steering response versus the stock suspension, with a lively feel that reacted almost immediately to driver inputs. Body roll was somewhat less than with the stock suspension, too.
Even with only 12,000 miles on the O.E. dampers, however, there was some minor high-frequency undulation felt when driving at speed over rippled expressways, or immediately after encountering larger bumps. The sensation felt as if the dampers could not quite control the stiffer spring rate of the Pro-Kit springs over certain road surfaces. At this stage, the ride was definitely not objectionable, but we expect the undulation sensation to increase over time as the Original Equipment dampers continue to age and wear. We also found this vehicle transmitted a little more impact noise than was heard in the car with the stock suspension.
The Pro-System Plus adds Pro-Dampers and upgraded Anti-Roll Bars to Pro-Kit Springs for a total suspension package designed to work as a team. Immediately apparent was the absence of the high-frequency undulation felt in the Pro-Kit Springs & stock damper-equipped car. This underscores the benefit of installing new performance dampers along with the performance lowering springs, rather than re-using the O.E. dampers. The installation time and effort is the same, so the only incremental cost is for the replacement dampers themselves. The car fitted with the Pro-System Plus took the handling improvement of the Pro-Kit car one step further, noticeably reducing body roll around the sweeping corners and faster on- and off-ramps along our route.
Overall ride quality was marginally firmer than the vehicle with Pro-Kit Springs and BMW dampers, particularly when encountering large single wheel impacts. The firmer anti-roll bars in this kit have little to no influence on ride quality when encountering a two-wheel bump, such as an expansion joint or railroad crossing, but will have some influence on ride quality when just one side of the vehicle encounters a bump.
The nice balance between ride quality and vehicle handling delivered by the Pro-System Plus makes us wonder why more vehicle manufacturers don't install this sort of suspension in their sport package-equipped cars.
The Multi-Pro R1 Coil-Overs have the most cachet and the best-looking components of the group. Shiny stainless steel threaded damper bodies with anodized adjuster knobs and race-car inspired 2.5" diameter coil springs provide the eye candy the other components can't quite deliver. Ride height is also adjustable thanks to the threaded damper body in the front and Eibach's custom adjuster in the rear. For our evaluation, ride height was set 1" lower than stock front and rear, giving the car an aggressive stance. The integral dampers are adjustable, too, with the compression and rebound settings changed by a single adjustment knob. For the road evaluation we set the dampers to a relatively mild two clicks up from full soft.
This vehicle displayed minimal body roll and a quick, nimble steering feel similar to the Pro-System Plus car. Sitting lower than any of the other vehicles, the car fitted with the Multi-Pro R1 Coil-Over Kit felt hunkered down on both smooth and bumpy roads, giving it taut but noticeably firmer ride. Despite the firmer ride, only the largest, sharpest impacts felt harsh. Our team was split on how much they liked the ride quality. For some this combination felt like a traditional performance car suspension should feel - firm enough to feel every bit of the road's texture without being so stiff as to become unpleasant. For others on our team, it was just a bit too firm, preferring one of the other suspension combinations in the test. The beauty of the Multi-Pro R1 Coil-Over system is the driver can fine-tune ride height and damper settings to suit their preference and driving conditions.
The car with Multi-Pro R1 Coil-Overs also had a somewhat heavier feel to the steering wheel than the others, requiring just a bit more effort to turn the wheel at lower speeds. This car also produced a modest increase in impact and road noise.
What We Learned on the Test Track
Our 1/3-mile per lap test track course includes 90-degree street corners, lane changes and simulated expressway ramps. Run in both dry and wet conditions, the test track allows our team to experience the traction, responsiveness, handling and drivability normally only encountered during abrupt emergency avoidance maneuvers or competition events.
For the track portion of our test, we used the adjustability of the dampers to help control body roll and weight transfer during transitions, increasing the compression and rebound rates of the rear dampers to near-full stiff. Front dampers were set at one click up from full soft, as higher settings caused the front end to chatter over the bumpy sections of the course. The goal was to improve initial turn in and manage the side-to-side motion through the slalom section of our course. The adjustment takes just a few minutes to do, and is something that can easily be done for an autocross or HPD (High Performance Driving) track event, then returned to the milder street settings for the trip home.
At anything less than 10/10ths on the track the coil-over-equipped car felt better than the other three cars, responding to driver inputs with authority. But when driven at maximum speed this vehicle displayed gentle understeer. The rear tires felt very well planted during steady-state cornering and were locked down during the rapid transition of the slalom section. There was no appreciable yaw in this vehicle to help the tires complete the direction change, forcing the front tires to do nearly all of the work. Overall steering response felt as crisp as the Pro-System Plus car equipped with stiffer Eibach Anti-Roll bars. But without them, the Multi-Pro R1 Coil-Over Kit car just didn't have quite as much cornering speed as the Pro-System Plus car.
Eibach Pro-Kit Springs: The Eibach Pro-Kit Springs lowering set improves your vehicle's looks and performance. Pro-Kit Springs lower the vehicle's center of gravity, reducing body roll in the turns, dive under braking, squat during acceleration and give the car a more solid secure feel at all times. Pro-Kit Springs also minimize the ugly fender gap that makes a car look "lifted." Eibach Pro-Kit Springs..."The look that performs." Read more.
Eibach Pro-System Plus Kit: The Eibach Pro-System Plus Kit delivers total suspension performance by including Eibach's Pro-Kit Springs, Pro-Dampers and Anti-Roll Kit. The Pro-System Plus is a precisely balanced combination tuned to operate as your vehicle's total high performance suspension system. Read more.
Eibach Multi-Pro R1 Coil-Over Kit: Eibach's Multi-Pro R1 Coil-Over Kits are race-ready and use a monotube damper design for maximum track performance. Ride height is adjustable between 0.80" to 2.5" lower than stock and the dual spring set-up is dialed for maximum cornering performance. The kits feature single adjustable rebound and compression damping as well as a monotube design with 46mm pistons for enhanced street and track performance. Read more.
Goodyear Eagle F1 Asymmetric (Max Performance Summer): The Eagle F1 Asymmetric is Goodyear's Max Performance Summer tire developed for modern high performance vehicles that are more advanced, intelligent and luxurious than ever before. However, since these vehicles are also more powerful, faster and heavier, they require tires that can provide control without conceding comfort. The asymmetric in the Eagle F1 Asymmetric name describes both the tire's tread design and internal structure, both of which are designed to enhance performance in dry and wet conditions. Like all summer tires, the Eagle F1 Asymmetric is not intended to be driven in near-freezing temperatures, through snow or on ice. Read more.