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How do IRS Subframe Connectors Help My Mustang?

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Running more ponies through your Mustang comes with it's on slew of hurdles. One of them being getting that power to the ground. Bracing your Mustang's body helps keep everything in place so you can come off the line with full force.

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Praise the Ford! After years of public prayer, the Mustang has permanently ditched its iconic live axle setup and joined the twenty-first century by utilizing an independent rear suspension, debuting with the 2015 S550.

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Benefits of IRS Subframe Connectors

  • Reduced or eliminated wheel hop
  • Increased chassis rigidity
  • Increased stability through turns
  • Augments traction

The implementation of the independent rear suspension in the S550 has also led to a new subframe design to house and support the unit. Those who drove Foxbody Mustangs back in the day may recall how flimsy the car felt, how it would flex under power and hard cornering. The solution to these frame twisting forces was to install an additional brace called a subframe connector. These connectors tied the front and rear subframes together, providing a stiffer, more unified body.

The S550 chassis has come a long way from its 80’s brother, and has indubitably arrived with many significant improvements. However, owners have been reporting that even with the new IRS there's noticeable wheel hop under hard acceleration and gear changes as well as flexing of the rear chassis when carving through corners.

The solution to this flexing problem, similar to the Foxbody era, is to install an additional bracing system to stiffen the rear subframe. Several aftermarket manufacturers have come up with an IRS subframe connector kit. Unlike the Fox subframe kits, which essentially run the length of the floor connecting the front subframe to the rear, the S550 IRS subframe kits are tailored specifically for the rear subframe. They do not connect to the front.

S550 Mustang Steeda IRS Subframe Braces
Subframe Brace Pair

What Causes Wheel Hop?

As mentioned, hard acceleration is the main cause of wheel hop in the S550. Hard acceleration causes the wheel to move independently of the chassis which causes changes in traction. In turn, the change of traction affects the motion of the wheel, and you enter a vicious cycle. Since the wheel is moving traction is changing, but because traction is changing so is the movement of the wheel. Here is a further analysis of the situation.

Upon launch, the car begins with good grip. The forces of acceleration cause the wheel to move forward within the wheel well, independent of the chassis. As the wheel moves forward, the toe of the tire changes and traction is reduced, causing wheelspin. Since the wheel is now spinning freely the acceleration force is quite small, and the wheel moves back into its original position. The toe of the wheel changes once again, and the tire now has a lot of traction. The acceleration force is now quite large and the wheel moves forward once again, having entered the vicious cycle that is wheel hop. The solution is to eliminate, as much as possible, the ability of the wheel to move independently of the surrounding chassis.

s550 Mustang Shelby Burnout
Shelby Mustang Burnout

How Does it Work?

The newly released subframe connector kits come as a two piece package – one brace per side of the car, mounting to pre-existing hard points (no modification of the car is required – they are direct bolt-in pieces). At the front, each brace (on their respective sides of the Mustang) connect to the front mounting point of the IRS subframe. A secondary connection is made at the rocker panel, and finally the third mounting point is made at the rear mount of the lower control arm.

Tying these three points together, in what is essentially a triangular fashion, really minimizes the movement of the wheel in relation to the IRS system, which allows for a massive reduction in wheel hop. Furthermore, as already mentioned, the braces add torsional stiffness to the rear subframe, allowing for less flex and more rigidity within the chassis which can easily be felt when cornering.

s550 Mustang Steeda IRS Subframe Braces
Subframe Braces Installed

When Should I Install IRS Subframe Connectors?

The answer to this question is quite straight forward. Going back to the Foxbody era (not again!), subframe connectors were the number one recommended modification no matter what. Similarily, IRS subframe connectors are a great addition to any S550 Mustang at any stage. Be it stock, mildly or fully modified, IRS connectors only enhance the handling characteristics of the S550.

They take care of a known problem, and do so in a relatively easy fashion. No major modification of the vehicle is necessary. Most bracing systems use factory mounting locations as connection points, thereby making the addition a true bolt-in upgrade. No welding or drilling necessary. Even better, throw in a matching IRS bushing support kit with the subframe connectors, and you’ll be wondering why you didn’t have this done from day one. They really can make that much of a difference.

s550 Mustang Steeda IRS Subframe Braces Installation
Subframe Brace Installation by Hand
Fitment includes: 2015, 2016, 2017, 2018, 2019, GT, V6, EcoBoost, ShelbyGT350