If you’re familiar with Project 5-Liter Eater, you’ll know that our 2015 EcoBoost Mustang has a variety of tasteful modifications installed on it. Recently, we addressed only a portion of the suspension by installing sway bars. One of the next pieces to the puzzle was to address our Mustang’s stance. And, because the new S550 platform uses an independent rear suspension (IRS), changing the rear springs on the ’15 Mustang is an all-new game.

To get our stance right and improve our spring rates as we continue to maximize the potential of our Mustang’s new IRS setup, we reached out to our friends at Vogtland North America located Temecula, California. The kit we’ve installed is Vogtland’s Sport Lowering Spring Kit, PN 387016 available for order. Project 5-Liter Eater is primarily serving daily driver duties, but the car is also our weekend autocross machine. Striking the perfect balance between all-out performance and daily comfort is why we went with the more balanced Sport Lowering Kit.

Here's a picture of Project 5-Liter Eater at stock height after installing the Roush RS1 Package.

Project 5-Liter Eater at stock height, after installing a Roush RS1 Package.

The Engineering Behind A Vogtland Lowering Spring

In most cases, lowering springs are designed to lower a vehicle and improve handling and performance. The manufacturing process starts in Vogtland’s facility in Germany, where springs begin as a concept for a vehicle. Leila Vizzari, president of Vogtland North America comments, “The material we choose for our springs is very crucial. Lower-grade material springs will lose their height over time due to the high-impact usage.” The springs are manufactured using a special oil-tempered steel and a mix of alloy materials known as high-tensile strength chrome-silicon (CrSi) and chrome-silicon-vanadium (CrSiV).

“The spring kits are tuned to function with the factory dampers. However, you can use our high-performance dampers that are available with the sport lowering springs as a suspension kit.” - Leila Vizzari, Vogtland North America

The next step in the manufacturing is the cold coiling process. It begins with the springs being tempered, followed by shotpeening, then preset to the correct lowering height and weight rating. The presetting phase of the manufacturing process is crucial. Vogtland chooses these materials to produce a lighter than stock spring that still provides high strength.

The material also effectively reduces unsprung weight on the vehicle, which ultimately translates into greater handling characteristics. Vogtland takes the process a step further after the presetting phase and seals the springs. The springs are phosphated and then powder-coated, which provides a long-lasting corrosion barrier from water and rust for years of service.


Vogtland Sport Lowering Springs

Vogtland Mustang Sport Spring Lowering Kit

  • Designed to give the Mustang a racecar “raked” stance
  • Lowers center of gravity and improves overall handling
  • Progressive spring rate: racecar handling when you want it
  • Powder-coat finish for optimal life
  • Lowering: one-inch front / one-inch rear
  • Compatible with all Mustangs including convertibles and coupes
  • Compatible on all Mustang OEM wheel and tire options
The springs are a progressive rate style, meaning they are a compound spring rate that provides an excellent ride quality under normal driving conditions, yet has the ability to also provide performance when being pushed close to their limit. As the spring travels, the rate of the spring will drastically increase. This means the spring consists of two different spring rates. The initial rate works to provide the compression necessary for proper, normal suspension functions on all road conditions. The latter rate is designed to keep up with the performance needed for neutral steering characteristics during spirited driving.

The springs provide two different “spring settings” for a balance between performance and comfort. Vizzari comments that these springs are made specifically for all ’15 Mustang models, both coupe and convertible. They’re also engineered to be compatible with all factory optional Mustang tire and wheel options. Rest assured, there won’t be any clearance or rubbing issues with these springs.

Vizzari also explains that these springs can be used with or without the factory shocks and struts, stating, “The spring kits are tuned to function with the factory dampers. However, you can use our high-performance dampers (recommended) that are available with the sport lowering springs as a suspension kit. That will ensure the end-user gets the most optimum handling and performance.”


Let The Installation Begin

The installation is fairly simple and straight forward. The springs are a direct replacement, which means there are no modifications required for installation. Since our ’15 EcoBoost has such low mileage, we chose to use the original shocks and struts. Keep in mind, whenever a car is being lowered, the entire suspension geometry is changed, including the steering angles. It is highly recommended to perform an alignment after installation.

Once you have a jack, and jack stands handy (or a lift), you’ll need the following wrenches and sockets: 1/2-inch ratchet, 13mm, 15mm, 18mm, 21mm, 22mm, 24mm, 17mm wrench as a panel removal tool; a hammer or mallet; and a spring compressor. Note that a 1/2-inch impact gun or breaker bar is necessary when removing the front strut from the strut plate.

From left to right: with the front wheel off the hub, start by removing the brake caliper. Next, disconnect the ABS line by popping off the clip, and remove the top bolt holding the sway bar end-link attached.

Loosen the two bolts holding the front strut assembly into the spindle. Note that those two bolts are splined, so you’re going to need a hammer now to loosen them. Now that the bottom of the strut is free from the knuckle, remove the nuts at the top of the strut assembly while holding the bottom of it so it won’t drop freely.

Before beginning the disassembly process, note that a spring compressor is required. If you're not comfortable using one, we highly recommend having a professional perform the installation for safety reasons. From top left to bottom right: with the strut assembly off the car, begin by compressing the spring, then remove the nut at the top. Decompress and remove the old spring. For reassembly, compress the new spring onto strut, then replace the bump-stop, strut tower bearing, and top hat, tightening the nut. To reinstall on the car, repeat the removal process in reverse.


To begin the rear suspension, start by removing the rear brake caliper, then disconnect the ABS sensor. Next, remove the rear sway bar end-link, then the bracket holding the rear brake line. Remove the top rear shock mount bolts. Support the rear lower control arm, then remove the two bolts cradling the rear subframe. Slowly release the subframe, using the weight of the subframe itself to decompress the spring in the lower control arm.

Have a friend assist you with a pry bar and pry in a downward motion on the lower controller arm. This allows you to slowly decompress the spring, removing it with ease. Before you install the new springs, transfer the factory isolates over and ensure the spring is seated properly. Lastly, use the control arm to compress the spring and bolt it back into place. As we mentioned, this process is identical for both sides, and fairly easy to complete.

The rear couldn't be any simpler, with only having to remove a few bolts and lowering the subframe or control arm.


The Verdict

Our stock height measured in at 28 3/8 inches for the front, and 28.5 inches in the rear (left image). After the installation, we drove the car a few miles, allowing for the springs to settle properly. The new height measured in with the front at 26 13/16 inches. The rear now measures at 27 13/16 inches. This translates to a total drop of 1 9/16 inches in the front, and 11/16 inches in the rear (right image).

These springs are made specifically for all ’15 Mustang models, both coupe and convertible. They’re also engineered to be compatible with all factory optional Mustang tire and wheel options. - Leila Vizzari, Vogtland North America

With the new springs installed, the ride quality feels much like stock in terms of comfort, yet more planted and connected to the road. When driving on uneven pavement or over bumps, we didn’t notice an increase in noise, vibration, or harshness over stock, and the car handles much better than it did prior.

On the autocross, steering characteristics also feel much tighter than before during turn-in. Because the car sits slightly lower now, our center of gravity has been decreased respectively. The rates are such that the rear-end isn’t too stiff, which could cause the rear-end of the car to rotate and feel non-linear. In the slalom, or in a hard sweeper, the higher spring rate was made present as the suspension compressed.

Aesthetically, we eliminated the factory truck-like stance. The car looks fantastic, and the ride-height is perfect. Not so low that we can’t navigate parking lots, driveways, and speed bumps.

Thanks to the lowering springs, Project 5-Liter Eater now has a more aggressive raked stance, improving the muscle-car look we think it needed. Keep in mind, our ’15 EcoBoost came from the factory with a slight rake. Since Vogtland springs are designed from the style of the OE spring, the lowering springs retained that rake. The springs really are a superb design, allowing for the car to be lowered the correct way.

Here is a comparison of the stock suspension (left) to the new height (right). We couldn't be any happier with the new stance Project 5-Liter Eater has acquired from the Vogtland lowering springs. The car feels more like a Mustang now, thanks to the definition and greater handling the springs have provided.