KJ Jones Senior Technical Editor
October 31, 2006
Photos By: KJ Jones

Horse Sense: It seems impossible to fathom at this point, but there was a time long ago when the "jacked-up" look was somewhat prevalent for late-model Mustangs. Today, "slam" is where it's at for a street 'Stang's posture, and the thought of a hard rake (back end up/front end down) or 4x4 stance makes us shudder.

We covered a lot of territory in our recent guide to the variety of suspension gear for Fox, SN-95, New Edge, and S197 'Stangs ("Handling the Options," Aug '05, p. 136).

Lowering springs and antiroll bars are featured in the Eibach Springs segment of the story. Installing either of these components is often one of the first upgrades a 'Stangbanger makes to a newly acquired Pony, be it brand new or new to him, and the modification wasn't done by the car's previous owner.

There's no doubt that a 'Stang of any vintage is supposed to sit low, be it a race car or a daily driven street car. Overcoming the travesty that is a Mustang's frightfully high body position-commonly referred to as ride height established by its coil-spring suspension-isn't difficult. There are quite a few options for bringing things down to a more socially acceptable level.

Installing the aforementioned lowering springs is one method, and going with a coilover suspension system that uses fixed-rate springs but offers a broader lowering range is another avenue for achieving the proper stance for your ride. Eibach's Sportline kit, for example, includes variable rate, nonadjustable springs that typically settle into a maximum 1.7-inch front and 2.3-inch rear drop on most Mustangs.

With either upgrade, your Mustang's ride height comes down from the boonies, and its handling characteristics also improve because of the car's lower center of gravity. Spring changes, when coupled with good antiroll bars and dampers, can eliminate dreaded body roll in corners. Springs also help reduce squat during acceleration and front-end dives when you're hard on the brakes.

We received information about Eibach's new Pro-Street-S series for '05-'06 Mustangs (PN 35101.711; $1,495) shortly after our suspension guide went to press, but we dig the next-level technology of this stainless steel front coilover/adjustable-rear-coil-spring kit. When we were given the opportunity to install one, we didn't hesitate to accept.

We're focusing on the kit that's made specifically for V-8 and V-6 S197 coupe and ragtop Mustangs. The new front assembly consists of a set of stainless coilover struts with 70mm, fixed-rate springs. When combined with the rear segment of the suspension system, it gives enthusiasts the ability to adjust ride height and corner weight for each wheel on their S197. The system is trick in its own right, as the factory coil springs are ditched in favor of a cool, adjustable rear-spring perch and a pair of progressive-rate lowering springs. Eibach Pro dampers replace stock shock absorbers in the rear, and shorter rear bumpstops are included and must be fitted in the OEM mounts.

Robert Lutes owns this white '06 Mustang, and he's no different from many other S197 owners who are ready to modify their brand-new cars. We called on our friends at B&D Racing in Canoga Park, California, to help put the drop on Robert's new Pony. B&D's chief engineer, Mason "Mase" Rowland, took on the assignment. In roughly an hour and a half, not including wheel alignment, he had Robert's '06 sitting at 27.5 inches in the front and 28 inches in the rear. That's considerably lower than the highboy stance of the factory 'Stang, with plenty of adjustment for a lot more "drop" left over.

From this rear-quarter vantage point, Robert Lutes' '06 'Stang looks high in the haunches. You'd think there would be a technical reason why Mustangs have such a high stance, but the company line on the subject isn't believable: "To provide clearance for properly installing snow chains on the tires." Right.

Robert's Pony measured 28.75 inches up front and 29.5 inches in the rear. With the car level, measurements were taken from the floor through the centers of the wheels and up to the lowermost portions of the fenders for both the front and rear of the car.

As usual when we work with B&D Racing, Mason "Mase" Rowland handles installing the Eibach Springs Pro-Street-S kit on this '06 'Stang. Once Mase has the car safely racked and the wheels off, he removes the OEM suspension components, starting with the stuff in the rear.

With the rear shocks already gone, Mase removes the Panhard rod and two coil springs. The rear antiroll bar can remain hanging from its link rods during this installation.

The factory rear-spring perch is removed and discarded. Note that Mase protects his hands with Mako gloves (PN IG101-color/size; $22.99) by Instinct Performance Hand Protection.

On the left is the original rear spring, and on the right is Eibach's progressive-rate (25mm-35mm-50mm) rear coil spring and adjustable spring perch.

The Eibach springs are considerably shorter than stockers, and the adjustment range of the new perches will enable us to bring the car down by 0.8 to 1.6 inches in the rear. As a starting index, Mase sets the rear springs in the highest position on the adjustable perches. He'll adjust the backside downward until the desired height is achieved once the entire suspension package is installed.

The adjustable rear coil springs are installed directly in the factory locations. There is no need to reuse the rubber isolator cup for either side.

It makes good sense to upgrade an '05-'06 'Stang's Panhard rod when converting to a coilover suspension to eliminate any drama when setting the wheel alignment. The Panhard rod controls the side-to-side positioning of the rearend housing and helps eliminate body roll in aggressive cornering. Mase puts a few turns on this BMR piece (PN PHR006; $129.95) acquired through RM Performance in Saugus, California.

The S197 Pro-Street-S system includes Eibach's Pro dampers for the rear. This is a simple shock replacement, and Mase has both sides done in no time.

The kit includes two replacement rear bumpstops that are a tad shorter than the factory stops to compensate for the new, lower height of the car.

After removing the original bumpstops...

...Mase presses the new ones into the factory bumpstop housings and reinstalls them on the rearend.

Eibach provides two spanner wrenches with each Pro-Street-S system. A spanner wrench helps make rotating the height adjusters in the front and rear a bit easier, especially once the springs are compressed. Adjusters on each spring perch feature a small Allen screw that serves as a locking screw to keep the adjuster from rotating once ride height is set.

Moving to the front, Mase indexes the outward-facing stud on the factory spring retainer prior to removing the front strut assembly. The stock spring retainer is used to secure Eibach's 70mm coils. Below the strut tower, the struts are dislodged from both spindles, and the ABS sensors and antiroll bar links are disconnected before the strut and spring package can be removed.

When assembling the front coilovers, make sure the spring is seated properly, with the end of the spring positioned against the edge of the rubber upper isolator, before installing and tightening down the retaining cap.

Installing the stainless coilovers is straightforward and basically a reversal of the removal steps.

Once again, Mase uses a spanner wrench to dial down the ride height.

Fine-tuning ride height with coilovers is one of the biggest PITA processes in a suspension upgrade, but it's the most necessary. As you see here, achieving the proper ride levels in the front and rear involves jacking up the car slightly, then raising or lowering the position at each corner. This is done in a step-by-step manner. After each adjustment, Mase lowers the car and measures ride height with a tape measure, then moves on to the next point (front or rear) to adjust where necessary until a spot-on match is achieved.

After a good wheel alignment and adjusting the Panhard rod to center the rearend...

...Robert's '06 GT is ready to rock. Eibach's Pro-Street-S suspension gives the profile the car should have. Mase screwed in a final ride height of 27.5 inches in the front and 28 inches in the rear, giving the 'Stang an overall drop of 1.25 inches and 1.5 inches (front and rear) lower than stock, with a lot more room for a lower stance to play with.