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Ultimate Guide 2015-2021 Mustang Suspension Kits

2015-2021 Mustang Suspension Kits

Whether you’re looking for better cornering or more bite off the line, there’s plenty that can be done to improve your Mustang Suspension Kits. Start modding now and feel the differences that even a simple chassis brace can have on your entire driving experience.

The stock Mustang suspension setup is great for daily drivers with no modifications, but it can leave a lot to be desired for your average gearhead. The mustang s550 suspensions kits made drastic improvements to the suspension setup from the factory, but still struggled in some areas. Regardless if you’re a drag racer or corner carver, upgrading your suspension will make you faster in a straight line and in the corners. This guide will give you an overview of all of the different parts and terminology regarding your suspension system, and what you need to know before upgrading Ford Mustang S550 Suspension Upgrade

Up until 2004, the late model Mustang’s rear suspension used a four-link setup. Two upper and two lower control arms hold the rear axle in place, giving the suspension its four-link moniker. Springs support the rear of the car, above the axle, with separate shocks installed to control the dampening. The main issue with this suspension type is how the control arms are mounted. Instead of running parallel to each other, they’re tilted slightly out. Combine this with Ford making their pony understeer like all hell, but when ran hard will snap steer. There are reasons why control arms, K-members, and more are on a bunch of wish lists.

Suspension Kits For Mustang S550
Suspension Kits For Mustang S550

Depending upon whether your Mustang is a V6 or V8, it has a 7.5 or an 8.8 inch rear end. The 7.5 uses an open differential while the GT’s 8.8 inch rear end uses Ford’s Traction-Lok differential. The 8.8 inch rear end was also equipped with quad-shocks during these years which helped dampen the axle and reduce wheel hop. A sway bar is installed on both versions of the rear end to help control body roll.

The rear suspension underwent a significant change in the 2005 model year in terms of how the rear axle is positioned under the car. The four-link suspension setup was nixed in favor of a three-link panhard bar setup, a compromise between a full independent rear suspension and a solid axle. A 3-link setup includes (2) lower control arms, but only (1) upper control arm.

An independent rear suspension would have added a substantial cost to the initial price of the Mustang. In addition, many Mustang enthusiasts prefer a solid rear axle anyway, as it’s more suitable for dragstrip duties. The panhard bar preserves the solid axle while providing cornering ability improvements that suit most owners better than previous Mustang generations. IRS setups allow both rear wheels to function and move independently of the other. This allows for greater control and handling. In IRS setups, there are two half shafts, one going from the driver side rear wheel to the differential housing and one going from the passenger side to the differential housing. Should you be driving down the road and hit a bump or a section of uneven pavement, your S550 Mustang will feel more planted than previous generation Mustangs as each side of the car is affected and responds independently of the other side. 

Although the system isn’t worlds different (technically speaking) than the incredibly common LRA setup, it does offer a whole new level of performance/handling. 

Differences & Benefits of IRS and LRA Mustang Setups

  • Live rear axle suspension systems are: 
  • More desirable for drag racing
  • Better at straight-line acceleration
  • Tend to be able to handle higher horsepower on stock components
  • Cheaper to service and replace

   Independent rear suspension setups are:

  • More desirable for track racing/handling
  • Less “squirley” and unpredictable
  • Provide a smoother ride
  • Can provide greater grip than LRA suspension systems

What Parts are Different on IRS Mustangs?

While the axle setup is one of the most obvious differences with IRS Mustangs, there are a handful of other parts that don’t transition over from LRA equipped Mustangs. While some of them serve the same purpose, the enhanced grip and articulation of IRS systems requires a few additional parts to control the car.

  1. Vertical Links – these basically replace the lower control arms on LRA setups and work to keep the wheels planted, especially under load. 
  2. IRS Bushings – unique to IRS setups, IRS bushings work to defeat deflection under load and wheel hop, reducing the amount of give/flex of the axles
  3. Rear Toe Links – serving a similar purpose and function as upper control arms, rear toe links allow the wheels on IRS S550 Mustangs to stay planted and adjust to lowered ride heights. These are crucial for maintaining a consistent and well-planted contact patch for the tires. 
  4. Craddle-Bushing Lock Outs – These help keep the IRS cradle planted and on the ground, cutting down on deflection and wheel hop.

Are S550 Mustang’s Good For Drag Racing? Will The IRS System Break? 

There seems to be this misconception in the Mustang and racing community that IRS equipped 2015+ Mustangs can’t quite hang with its predecessors in the quarter mile. An IRS powered S550 Mustang can be as competent as the Mustangs of yesteryear and can easily dip into single digit time slips.

Just like LRA Mustangs, and IRS S550 will need a little effort to perform at the top of its class, which mainly comes from replacing the half shafts. The half shafts are the biggest weak point in the whole system and can fail, especially when launched at the track on a sticky tire. Luckily for enthusiasts, aftermarket half shafts are readily available and easy enough to replace.

Half shafts are rated by the amount of horsepower they can safely withstand, allowing you to pick a set ideal for your build. If you are shooting for an S550 that puts down 600 HP and runs 10s, you don’t need the biggest, baddest half shafts available. You can buy ones rated for 800 HP rather than the 1k shafts.

Read About : What is the brutal truth about owning a Ford Mustang?

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