Shock, Spring, and Coil Over Product Guide
There are more suspension options available now than ever before. And it's easy to get lost among the different types of suspensions and the various levels/variants within them. We have written up this guide to give you the inside scoop on the different suspension options you will commonly find for sale.
|Shock/Spring Package - $600-$1,500
A direct 1:1 replacement for your existing struts, shocks, and coil springs. This is the easiest and most basic suspension package as most of these Packages are direct replacements for the existing components. Most of our Packages install with the stock, original mounts for a seamless and hassle-free install. The springs will lower the ride height by a fixed amount but will not be a radical change in most cases. The ride will be stiffer than stock by about 25-40% depending on the application. But in most cases the shocks and struts keep the ride civilized and composed. Camber correction kits are generally not required even though the negative camber alignment will be increased.
Examples of Shock/Spring Packages:
|Coil Over - Street - $1,000-$4,300
Street coil overs are very similar to a shock/spring Package but with additional features. A coil over is any suspension kit where the ride height can be adjusted up or down. Coil overs used to be only for racing or track cars but changes have been made to make them street friendly. Most street coil overs install with the stock strut and shock mounts. The springs are generally close to, or the same, as Sport springs found in our Packages. The ride height is typically adjusted between a 1.0" to 2.5" drop from a stock ride height. Front struts have threaded bodies and a threaded lower spring perch (like a bolt and nut) that allows the spring to be lower or higher. The rear is typically an adjustable perch above or below the spring. Most BMWs do not have the structure to support a true coil over in the rear.
Aside from the height adjustment, the main advantage of a coil over is that the shock travel and spring travel are engineered together. In a Package of separate shocks and springs you have two different sets of engineers designing two different products. In most cases they work well together. But having the complete assembly designed by one team of engineers is more ideal. This ensures both the spring and shock/strut have the correct amount of travel.
Camber correction kits are generally not required unless the vehicle ride height will be dropped beyond 1.5".
Examples of Street Coil Overs:
|Coil Over - Track - $1,300-$6,000
A Track coil over has the same basic principles and design as a street coil over but with a few key changes to the spring and shock rates to make the car perform better on the racetrack. A racetrack tends to be a smoother and more consistent surface than a street. And the cornering speeds are a lot higher. This means the forces that the weight of the car places on the suspension are a lot greater. And this requires greater strength from the springs and more control from the shock absorbers. While a street spring may have a rate of 350lbs-inch, a track-only spring may be more in the 800lb-inch range (examples given, actual spring rates vary). Simply put, the track suspensions simply do not have the absorbing qualities as a softer street suspension.
Track suspensions also use specialized mounts and hardware. Because the ultimate goal of a track car is to be the fastest or have the perfect handling balance, suspension mounts need to be adjustable and supremely consistent. Most track-only suspensions use an adjustable camber/caster plate and solid hardware (no rubber). Rubber will deflect and deform and allow alignment changes. This is important for a street car that sees potholes, railroad crossings, etc but unnecessary on the racetrack.
Typcially, a Track coil over differs from a true Race coil over in that there are fewer adjustments for the shocks to limit the spring rate range and the cost is much lower.
Examples of Track Coil Overs:
|Coil Over - Race - $3,500+
True racing coil overs are more finely engineered for the given application. The suspension geometry of a race car is different than a street or street-based track car. Therefore the strut and shock designs are much more applicaton specific than an off-the-shelf track coil over. The spring rates of a race car are typically even higher than what is used on a track coil over and this means a different range of shock damping rates as well. Racing coil overs will also have more adjustments for shock velocity - low speed compression, high speed compression, low speed rebound, and high speed rebound, and possibly more. Adjustments made to each setting require a very high understanding of suspension performance and behavior with detailed data collection and analysis. Racing coil overs can run well over $10,000 per set because of the limited production and advanced engineering and technical features.
Examples of Race Coil Overs:
|Front Camber Kit
BMWs are set by the factory to understeer. The front tires will lose grip before the rear tires. This is more predictable and controllable than having a tail-happy car. Giving more grip to the front tires will make the car corner faster and to accomplish this you want to add negative camber to the front. After shocks/springs, adding negative camber would be our second step in improving handling. The camber is the vertical angle of the tire, tilting to the inside or outside of the vehicle. Tilting the top of the tire to the inside will give more surface contact when the car is cornering. The idea is to get as much of the tire's width flat against the pavement. Different corners have varying demands for grip; there's not one universal 'sweet spot'. Under street conditions you will never need so much negative camber because you're just not seeing the types of corners that require it often enough. On-ramps and off-ramps provide similar speeds and cornering forces but you're not hitting those corners in a series for 20 minutes at a time.
|Swaybars / Anti-Roll Bars
After fixing the understeer with camber plates, our next step in making your BMW handle better is to add larger sway bars. When cornering the car's weight will shift around as the body rolls. By forcing the body to stay upright you have less weight transfer. This makes the suspension much more effective. You get quicker turn-in and less bodyroll. The larger swaybar has more leverage to better control the body and suspension motions. In general, we have found that a very large front bar, paired with a rear bar of equal or slightly larger size, is best for balancing a BMW and reducing understeer.
E36 Track Day Upgrades
Watch how tire, suspension, brake, and engine upgrades add up to faster lap times on the track! We took a tired, bone stock 1992 E36 325is to Monticello Motor Club for a day to see how improving the car one stage at a time leads to faster lap times.