First iterations of new technologies are rarely flawless. When the Mustang ditched the solid axle in 2015 in favor of a 21st century Independent Rear Suspension, it transformed into a modern-day sports car with greatly improved ride quality and handling dynamics. Unfortunately, the new diff and subframe are mounted with soft, compliant rubber bushings that cause a significant wheel hop when launching the car and unwanted toe changes in corners. This affects drag and road racers alike. In order to eliminate these issues, we tested Steeda Autosport’s Ultimate ‘Stop the Hop’ Package and Adjustable Differential Bushing Insert System.
The S550 Mustang was introduced in 2015 and has a lot of soft rubber-mounted suspension components to reduce noise, vibration, and harshness (NVH) but is counter-productive for performance and handling. The differential is attached to the subframe with large, soft rubber bushings that have voids in the top and bottom. This causes the diff to have a significant amount of vertical movement even under moderate load. The subframe is then mounted to the chassis via more large, soft rubber bushings which cause the entire rear suspension to pivot and move under acceleration and cornering. This makes the chassis less responsive, consistent, and predictable. While our bone stock 2016 Mustang GT out-handled our 2009 Project E90 M3 in our Continental Tire ExtremeContact DW Tire Test, reducing this unwanted flex will further improve the Mustang’s already impressive capabilities.
We reached out to our friends at Steeda Autosports for their expertise on fixing this problem. Steeda has been modifying Mustangs for nearly 30 years and is one of the world’s largest aftermarket parts manufacturers for Fords. They recommended their Ultimate IRS ‘Stop the Hop’ Package (p/n: 555-2129) which is available for all 2015-2017 Mustang GT, EcoBoost, or V6’s and is designed to reduce wheel hop, provide increased traction, and improve overall handling characteristics by stiffening the IRS subframe bushings.
Our Steeda ‘Stop the Hop Package’ came nicely boxed up and we were eager to get them on the car.
The ‘Stop the Hop’ Package incorporates Steeda’s Bushing Support System which uses aluminum inserts to fill in the gaps of the rubber bushings. The bushing becomes fully encapsulated and movement is limited under heavy load. This effectively acts like a stiffer bushing but with minimal effect on NVH since the soft rubber is retained.
This package includes Steeda’s Subframe Alignment Kit which uses Delrin inserts to ensure the subframe is centered and aligned with the chassis. This is crucial for straight launches off the line and consistent handling right to left. In stock form, the inner diameter of the OEM bushing has half an inch of play which can allow the subframe, suspension components, and tires to be offset forward, aft, or side to side by as much as a quarter inch from center!
Also included in the kit are the Billet Aluminum Steeda Vertical Links (aka: Integral Link), which feature billet steel bushings that further reduce deflection over the factory rubber bushings in the stock links.
