Eibach Pro-Kit springs will:

• Lower your S550 Mustang, improving appearance
• Reduce body roll when cornering and nose-dive when braking, because the spring rate is higher than stock springs
• Quicken steering response because the spring rate is higher
• Lower the center of gravity, improving handling

• Progressive system rate
• Made of premium-quality high-tensile alloy spring wire
• Powder-coated for long-lasting protection and great looks

Eibach measures spring rates as a system, including 10mm of bumpstop deflection. That added bumpstop rate contributes to the final rate of the system, the higher number listed below:

Front system rate: 200-314 lb/in
Rear system rate: 800-914 lb/in

Approximate lowering:
2015+ Mustang GT hardtop and convertible: (Front: 1.1", Rear: 0.9")

Fits
2015 S550 Mustang GT, hardtop and convertible

Does NOT fit
S550 Mustang with Ecoboost or V6 engines

Installing aftermarket springs involves more than just the spring installation itself. To get the full benefit from your spring purchase, there are several related factors to consider:

Alignment
Lowering a Mustang changes its front alignment. The relative lack of adjustment features can sometimes make it difficult to restore the vehicle to Ford camber specifications without using an aftermarket solution. That's why we created our MM Caster Camber Plates, which extend the range of camber and caster adjustment so you can realign to factory specs.

Struts and Shocks
Ford matched the valving in the original struts and shocks to the original stock spring rates. Most aftermarket springs are stiffer than the stock springs--enough to cause an underdamped situation, meaning the struts and shocks (the dampers) cannot control the springs. That makes the car feel floaty, disconnected from the road, and harder to control. The solution is to install dampers matched to the new, higher spring rates.

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Do I need to do an alignment after I install springs?
You should always check the alignment after changing your Mustang's ride height. For the stock alignment specs, see your Mustang's factory service manual. For high-performance alignment specs, see the MM caster camber plate instructions, or contact an MM Tech Associate.

Which are the front and rear springs?
Eibach includes printed instructions with each spring set that include information about identifying front and rear springs.

Do I need to modify the bumpstops?
Not unless the information that came with your spring purchase specifies this step.

Do springs ever wear out?
The term "wear out" isn't accurate when applied to springs. The spring rate will never change over time because rate is determined by the spring wire diameter and the length of the wire before it is wound into a coil. The rate cannot change without physically changing either the wire diameter or its length.

On the other hand, "spring sag" may occur. This means that the spring's free length has changed because its coils are closer together than they were when manufactured. However, this is very unusual with the newest spring steel alloys and modern manufacturing processes used by reputable spring manufacturers. Spring sag has no effect on spring rate, because sag (change in free length) does not change the dimensions of the wire itself. However, the reduced ride height can adversely affect the suspension geometry, and cause the suspension to bottom out more frequently.

The majority of ride-height reduction over time is caused by degradation of the spring isolators located at each end of the spring, not from spring sag.

Springs can also break. This is usually due to stress risers on the spring wire, such as pitting caused by corrosion. This is one reason to use spring isolators, as they protect the springs' coating from corrosion.

Will the ride height change if I remove the spring isolators?
Yes.

How do I know the amount that Eibach springs lowered my Mustang?
Measure your Mustang's ride height before and after installation.

When measuring ride height the most important thing to keep in mind is to be consistent in your technique. For instance, have the same amount of fuel on board. At MM we always fill up the tank immediately before measuring ride height, and set the tires' air pressure. Park your Mustang in the same level spot. Always measure between the same two points, such as from the ground to the top of the fender opening, or from the wheel lip to the top of the fender opening. Counting how many of your fingers fit into the gap between the top of the tire and the fender lip does NOT qualify as proper measuring.

Do I need to use the isolators and tubing?
All aftermarket springs for Mustangs are designed to reuse factory tubing and isolators to prevent premature wear and excessive noise. Notice any protective tubing on the factory springs and take note of its location for reinstallation.

General Notes
Measure your Mustang's ride height before and after installation. The most important thing is to be consistent in your technique. Have the same amount of fuel on board and the same tire pressures. Park your Mustang in the same level spot. Always measure between the same two points. We suggest measuring from the wheel lip to the top of the fender opening. Counting how many of your fingers fit into the gap between the top of the tire and the fender lip is NOT reliable measuring.

With rubber control arm bushings it's important to pre-load the suspension before tightening the suspension pivot bolts. The easiest way to do this is by allowing the full weight of the vehicle to rest on its tires on an alignment rack or ramps. You can also use a lift or jack stands, lifting each suspension corner and tightening all pivot bolts. Correct suspension preload while tightening pivot bolts will result in more consistent lowering, and will greatly extend the life of the rubber pivot bushings. Unlike rubber bushings that twist rather than rotate, urethane bushings and spherical bearings do rotate, and therefore do not require preloading the suspension while tightening the pivot bolts.

Use the proper spring compressor to remove springs from your car or when disassembling a coil-over strut. Springs store a lot of energy, and can cause serious injury and/or damage if suddenly released.

Take note of the routing and mounting positions of all brake lines, wires, and cables before modifying your suspension. Failing to reinstall the lines in the factory position can cause damage or brake failure.

Before removing springs, label every component from top to bottom with sequential numbers. This will help you reassemble the new and existing parts in their correct order.

Before taking the strut assembly apart, use a marker to draw a vertical line across each component to indicate its original factory orientation. This will help you reinstall all the OE parts correctly.

Mark the position of all alignment-related mounting bolts to provide a good starting point for the post-installation alignment.

Work on one corner of the car at a time. Strut assemblies have parts that must be assembled exactly in factory order. If you make a mistake or lose track, you can refer to the other assembly.

Reinstall all bolts in the same orientation (i.e., up or down) as they were installed originally.

All aftermarket replacement springs for Mustangs are designed to reuse factory tubing and isolators to prevent premature wear and excessive noise. Notice any protective tubing on the factory springs and take note of its location.

Don't let the spindle or brake caliper hang from the brake line, as it can damage the line and cause premature wear or even failure.

To help prevent spring noise on rough roads, leave a 1/4" - 1/2" space between the end of the coil and the end of the spring seat pocket.

Spring isolators reduce the transmission of road noise into the passenger compartment. Age alone will deteriorate rubber isolators as much or more than mileage does. Replace the isolators whenever installing new springs. All new springs for Mustangs are designed for use with new isolator pads. Using worn pads could cause increased noise and improper ride height.

Always use a torque wrench for final tightening to factory specs. Never use an impact gun for final tightening of any bolts or nuts, as they tend to over-tighten small bolts and under-tighten large bolts.

After the first 500 miles on new springs, and after each track event, re-torque all mounting bolts.