ST Suspension’s Full Coil-Over System for the LX Platform

Vortech Supercharger system for LX vehicles producing about a 100hp gain

It’s a funny thing, while we all like to talk up horsepower, the reality is that nine times out of ten, people are more critical of a car’s ride than anything else. In fact, it’s the body roll, yaw and handling characteristics that divide the field between sporty cars and sports cars.

Considering this, particularly in the case of our look-at-me-red Magnum project wagon, we knew that all the extra horsepower on the planet couldn’t compensate for the weak suspension.

Here at the powerTV garage, we get our grubby hands on some of the coolest car parts out there. Our latest addition to the performance parts lineup is from ST Suspension who provided a performance coil-over kit and anti-sway bars for our 2007 Dodge Magnum R/T.

To recap what we’ve done thus far, powerTV’s 2007 Dodge Magnum R/T has been supercharged by Vortech, has a completely new exhaust system using SLP performance headers and a Flowmaster cat-back, plus a custom tune by Diablosport that brings our power to just over 450 horsepower at the tires. That’s a pretty good number for a sport wagon.

ST Suspension stepped in to provide a full coil over suspension kit, fully adjustable, and also included its performance anti-sway bars.

Introduction to ST Suspension

It all began in 1979, in Southern California when ST began developing innovative suspension products in response to market demands. The success of the company and its core technologies attracted the attention of many tuners resulting in countless private label projects of what became many of the largest names in vehicle suspension tuning in the USA over past 30 years.

The Sporttech and Speedtech lowering springs along with the ST sway bar kits became a household name in the tuning scene in the 80’s and 90’s, being referred to in many circles simply as ST. In 1995, this attention attracted a new owner, Belltech Sport Trucks, who brought a whole new dimension to the ST lineup, particularly for Sport Trucks. As part of the deal, ST was relocated from Southern California to Fresno, CA.

In 2005, the German suspension powerhouse KW Automotive, well known for its reference standard KW coil-over adjustable height suspension systems, purchased both Belltech Sport Trucks and Suspension Techniques and launched KW Automotive North America Inc.

Now based just outside of Fresno in Sanger, CA., the infusion of technology from the new parent company took ST’s game to a whole new level. The move increased not only its application range, but also added (among other things) the innovative ST Speedtech coil-over program, modeled after the wildly successful galvanized KW Variant 1 coil-over program.

With this influx of worldwide technology, staff, and engineering base ST boasts one of the largest application ranges and largest distribution chains of any suspension manufacturer in North America.

This is the ST Coil-Over Strut Suspension (PT# 90281) that comes complete and ready to bolt in to the Magnums stock suspension mounting points, hassle free.

Strutting Your Stuff

ST Suspension's MacPherson strut allows for complete adjustability, allowing for ride height and dampening corrections.

The ST Suspension provides all around performance, providing a balance between performance and comfort for everyday use. The suspension components include a lightweight, composite spring cap that holds both the helper spring on top and the high-strength main coil spring below. This is to preload the main springs to prevent unnecessary movement and noise. The shock it self has a hardened chrome piston rod inside a zinc plated strut housing coated for corrosion resistance and long term durability.

The technology behind the suspension is adopted from ST Suspension’s sister company, KW Suspension. We talked to KW Automotive’s Marketing Manager, George Ciordas, who explained that, “The dampers are built to withstand both the challenges of the street and the demand of the race track.”

Each strut is built with a twin-tube shock absorber, where the piston works inside of an inner tube. The space between the inner tube and the casing is used as an equalization chamber. Changes in volume due position of the piston rod change the oil level in the equalization chamber between the outer casing and inner tube.

When the car swings downwards in the direction to the road, the piston rod is moved downwards. The oil displaced by the piston rod is pressed into the equalization chamber between the tubes via specially designed orifices in the compression valve at the lower end of the inner tube.

The resistance that is created through this valve creates the actual compression forces. Oil underneath the piston also flows upwards through the piston check valve with low resistance which also influences the damper characteristics.

When the car swings upwards, away from the road, the shock absorber is extended. The rebound phase valve at the lower end of the tube resists the oil that flows downwards through the holes in the space above the tube, slowing down the upward motion. When the piston rod is pulled out of the case, its volume is balanced out by the oil that flows from the equalization chamber back into the inner tube through the compression check valve.

ST Coil-Over Suspension - Front struts and springs.

The ST LX Suspension Kit (PT# 90281) includes:

  • Matched damper and spring rates, which provides excellent balance between performance and comfort
  • Corrosion resistant Zinc plated threaded strut housing
  • High quality construction – manufactured in Germany by KW suspensions
  • Competitive entry level price point
  • Provides corner weight and height adjustability for optimum handling balance
  • 5 year warranty

ST Suspension front and rear sway bars include the rubber bushings to mount directly in to the factory mounting points.

Taking Out The Rockin’ and Reelin’

When tuning your vehicle’s suspension, there are many ways to change your vehicle’s handling characteristics. Springs, dampers and alignment all play huge parts in affecting how your vehicle handles, but no component has as drastic effect on your body roll as the anti-sway bars without adversely affecting your ride quality.

To the average enthusiast, the installation of a ST anti-sway bar kit (PT# 90281) will drastically reduce the boat-like feel that many LX vehicles have with the factory, or even mildly tuned suspension. By increasing the rate of the front, rear or both bars over the factory units, the body roll will be reduced giving you more confidence on long sweeping corners, on and off ramps, as well as in emergency maneuvers.

Ciordas continued, “The ST anti-sway bars are built with additional adjustability in the bar itself with multiple end link mounting points and with adjustable heim joint end links to tune in the most desirable handling characteristics (think over- and under-steer).”

“ST’s kits are available for the front and rear separately or in complete package for a large range of vehicles. Each ST anti-sway bar is designed and produced in-house and are constructed from high quality steel and powder coated for durability,” explained Ciordas.

ST Suspension provides - at an additional cost - front and rear performance sway bars (PT# 90281) to reduce body roll. This is a perfect match to the coil-overs.

Down to The Nitty-Gritty

Now that we have all those technical details out of the way, it’s time to get to the suspension install process. ST Suspension builds their coil-over kits to be a direct factory replacement suspension so there is no need to pull out the grinder or the plasma cutter.

The first step in removing the factory struts and springs was getting the Magnum up in the air. While most of you won’t have access to a two-post lift like we did, a sturdy set of tall jack stands will work. Next, we pulled off the wheels using a 21mm socket and, working our way back to front, removed the rear shocks using an 18mm and a 15mm socket.

Dropping the rear cradle is the easiest way to install the rear shocks and springs. It's a matter of taking out four bolts and the entire rear end drops, making it easy to get to the suspension components.

Installing the ST Coil-Over (PT# 90281) front struts was easy. Just a few bolts and the suspension slips right in.

One of the advantages of the Magnum R/T was its self-leveling rear shocks, ideal for carrying an extra load in the back. While this is great for towing or delivering large heavy packages, this is a sports wagon made for performance, not towing.

As fair warning, removing the rear springs can be a bit of a challenge. We found that access was rather difficult until we opted to drop the entire rear cradle, rear end and all. This might sounds like a monstrous process, but dropping the rear cradle lowers the spring perch enough for the rear springs to slide right out.

Surprisingly, this is pretty easy, just undo a four bolts with an 18mm socket, and the cradle can be lowered slowly with a floor jack (that is, of course, if you’re doing this on jack stands). Since the rear end has hard steel brake lines connecting it, we were mindful not to lower it too far.

The rear springs ST provides slip right in to the stock position along with the rear dampers. They are a bit shorter, so we brought the entire cradle up a bit to fit the dampers and springs in to position.

The rear dampers feature the same composite spring seat that screws up or down along the base of the shock. This allows you to customize the ride height on all four corners of the vehicle to have a perfect ride.

Since the front uses a McPherson-style strut including an upper A-arm mounting point, our installation wasn’t as intensive. With the Magnum off the ground and top and bottom bolts holding the strut in place loosened, the relaxed upper and lower control arms allow for for the strut to slide out with little trouble.

Inserted ST Suspension’s replacement strut was as effortless as removing the factory unit. The top of the strut mounts to the strut tower and is tightened down through the engine compartment while the bottom mates up to the lower control arm with a single bolt.

We adjusted the suspension to it’s lowest position using the composite spring seat that screws up or down along the base of the shock, giving us a “zero point” from which we could adjust up from.

Ride height is obviously a factor when installing suspension. The ST coil-overs adjust easily and we measured each corner to ensure we were level. You can adjust each strut to get that perfect ride height.

The ST performance sway bars fit directly into the factory positions. Luckily, the front stock position of the sway bars was easy to get to and is only fastened by a couple of bolts; two at each of the two subframe mounts requiring a 15mm socket and one at the endlinks requiring a 21mm and 10mm wrench. This makes it so there’s no need to remove the belly pan in the front.

ST includes a rubber bushing for each side so you don’t have to keep the stock ones. Just seeing the stock and ST sway bar side by side was convincing enough that the driving experience was going to be different once we were done.

Although the diameter of the front ST sway bar is significantly larger than the stock (35mm over the factory 30mm up front and 19mm over 15mm in the rear), the ST sway bars bolted right in with out any issues.

The rear sway bars, much like the entire rear suspension, was of course a bit more challenging than the front. Since we had the rear cradle dropped already, it was much easier to install.

The rear sway bar is positioned up and over the gear box and mounts to two tie rods that bold to each rear knuckle, needing a 15mm socket. The factory bushing brackets are easily removed with the same socket size, and the old bushings are quickly replaced with ST Suspension’s new ones.

When finally installed, the rear sway bar fits nicely but a little snug as the diameter of the new sway bar is slightly larger than the stock.

With both the front and rear kits installed, it was time to put the wheels back on and lower the car to the ground. Our job wasn’t completely over however. The ride height needed a bit of adjustment first before the Magnum was ready for the road.

Using a tape measure, we measured the height of each wheel well and adjusted the composite spring seats on all four corners of the car until the optimal ride height was reached.

We dropped the Magnum to the ground and immediately the front wheels tucked nicely up in to the wheel well. It's time to take it to the road and see how she handles.

Pedal, Meet Metal. Metal, Meet Pedal.

Our fancy glamor shots of the Magnum clearly show the height difference. Overall, we dropped the car about 1.8 inches respectively from the stock ride height.

The Magnum rolled out of the powerTV garage with a fully loaded performance suspension dropping the car a total of 1 5/8-inches over the factory strut and spring settings. We adjusted the rear ST Suspension struts to purposefully eliminate the factory rake, as well, giving the Magnum a more low-slung look.

The car not only had a new aggressive stance, but also displayed better cornering prowess and a stiffer, more race-like ride when we took her out to stretch her legs. While weren’t able to get the scientific later-g measurements we would have hoped for, we were able to put the Magnum through the paces on our local twisty mountain roads.

From the factory, the R/T Magnum weighs in nearly as much as Dodge Ram 1500. Considering that, we were really impressed how well the big wagon took to the curves and hairpins. In combination with the extra power we’ve packed in to the Magnum, this suspension setup from ST was a perfect match.

The added rigidity of the anti-sway bars combined with the rebound dampening and fluid motion of the struts keep all four corners glued to the asphalt at all times. And since we were running on the same tires we had before, we knew we weren’t cheating.

Body roll was effectively eliminated as well, which is impressive given that the R/T package already came from the factory with pretty stout sway bars and springs. We pulled as hard as we could while still being safe – seeing that we were driving on surface roads and not a closed course. Time and time again, our lil’ red wagon hooked the turn and bit hard, accelerating out of the big end.

Our 2007 supercharged Magnum R/T is now fully equipped for both road and track conditions. The complete coil-over system provided by ST Suspension and the ST performance sway bars mate perfectly with the Magnum’s long wheel base and heavy chassis. It’s apparent ST put a lot of attention in designing and testing their suspension solutions for the LX platform and expertly converted this HEMI-powered wagon from a sporty car into a sports car.

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