KellTrac Innovations Puts Positive Pressure On S550 IRS

When Ford Motor Company designed the independent rear suspension (IRS) on the S550 Mustang, it had to pair creature comforts that drivers look for with performance that enthusiasts desire. A very difficult task at hand, especially when it could possibly introduce noise, vibration and harness (NVH) into the mix. So, as with any manufacture they decided to give way to the majority of their market. Those looking to expand their Mustang’s capabilities on the performance spectrum were left with adding aftermarket products to their liking in order to promote the driveability they want.

Kelltrac

That KellTrac Level 1 S550 Mustang IRS Bushing Upgrade Kit can be found on record-breaking S550s. The kit is also utilized on Palm Beach Dyno and Evolution Performance serialized builds.

One key complaint from most spirited drivers is the deflection that can be found when using the factory rubber control arm bushings. This unfortunate situation causes handling to be disrupted and the dreaded wheel hop on hard launches to take place. While the rubber bushings have the ability to keep NVH to a minimum, it provides less-than-adequate handling tendencies for those looking to push their platform. To correct this, KellTrac Innovations has produced a kit that not only helps eliminate deflection, but positively locates the rear IRS subframe and the rear lower control arms within the chassis.

The KellTrac Level 1 S550 Mustang IRS Bushing Upgrade kit is more than a few fancy polyurethane bushings in a bright color though. The kit can be dissected into three major groups that promote the IRS’s handling and launch performance capabilities. The first is the PosiLoc which eliminates deflection that can cause poor handling tendencies and wheel hop. The second piece to the Kelltrac Level 1 kit is the Polyurethane Centering Sleeves that complete the squareness of the IRS subframe when mounting to the vehicles.

Kelltrac

The level 1 kit while simple in appearance has the ability to enhance the IRS’s handling and launch performance capabilities.

The final piece is the Rear Control Arm Bearing kit that utilizes bearings from BMR Suspension. The Rear Control Arm Bearing kit removes the factory rubber bushings and adds a Spherical Bearing kit to positively and precisely locate the rear axle knuckle assemblies within the chassis to further prevent deflection. Although the market tends to avoid these RLCA bearings due to installation time and fear of drastic NVH increase, this upgrade has been proven to be a great modification to the S550’s IRS System. Since BMR Suspension’s customers had great success with the RCLA bearing kit, KellTrac chose to include it within its variety of suspension packages. The final piece to the KellTrac Level 1 kit is the Polyurethane Centering Sleeves that completes the squareness of the IRS subframe when mounting to the vehicles.

As you begin to modify your Coyote-powered Mustang, the suspension will quickly become the bottleneck for on-track performance. Instead of going full-tilt with a complete suspension package, which Kelltrac also offers, you can start with their Level 1 kit and take your stock IRS much further without worries of dramatically higher NVH levels. So, if you sway more towards the enthusiasts side and desire better handling out of your S550 hit up KellTrac Innovations.

About the author

James Elkins

Born into a household of motorsport lovers, James learned that wrenching takes priority over broken skin and damaged nerves. Passions include fixing previous owners’ mistakes, writing, and driving.
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