For many enthusiasts, the addition of independent rear suspension (IRS) on the 2015+ S550 Mustang was seen as a vast improvement when it came to handling and brought the car into “modern times.” But nothing is perfect and as excellent as the S550 performs, it still suffers from wheel hop.
For drag racing purposes, wheel hop can be detrimental to track times though it is incredibly stressful on any car.
To find out how to get rid of wheel hop on your S550 we reached out to Kelly Aiken, the Mustang specialist at BMR Suspension.
What is Wheel Hop?
Wheel hop occurs during hard acceleration when the rear wheels are not well-controlled by the suspension and struggle to maintain grip. This is a result of the toe angle changes when accelerating, causing the wheels to appear to hop or jump, quickly and violently.
Think about “John the Mountaineer” going uphill in the third season of The Grand Tour when Clarkson, Hammond, and May travel to Mongolia. The front wheels of John going up a hill serve as an exaggerated and extreme example to provide a strong visual of what’s occurring when wheels hop.
What Should I do First to Reduce Wheel Hop?
According to Aiken, the first thing you should do to reduce wheel hop is to address one of the most significant causes: cradle bushing deflection.
From the factory, the S550 utilizes rubber bushings that allow for a significant amount of deflection and differential movement. For most S550 owners, to reduce movement, and as a result, lessen wheel hop, Aiken recommends the Cradle Bushing Lockout Kit (CB005).
The BMR kit utilizes billet aluminum upper bushing lockout rings to secure the inner bushing sleeve and the outer lip of the bushing cup on the cradle, while, the lower bushing locating washers are positioned in the bottom portion of the bushings’ inner sleeves. By stabilizing both sections of the bushings’ inner sleeves, nearly all movement on the plane, fore/aft, lateral, and vertical, is eliminated.
Additionally, the kit replaces the factory sheer plates with bolt-on cradle braces which stabilizes the cradle so that it can’t change position under any form of driving.
Aiken shared that as a result of their research and development, the kit reduces 80 to 90-percent of fore/aft and lateral cradle bushing deflection.
“For a more race-oriented S550 with sticky tires there will be slightly less of a reduction,” Aiken said. He added that the kit is the only part you need to affordably and effectively lessen wheelhop, bushing deflection, and cradle movement. Additionally, changes in noise, vibration, and harshness (NVH) were nearly nonexistent.
How Do I Eliminate Wheel Hop?
According to Aiken, one of the most overlooked components in addressing wheel hop are the rear lower control arm bushings. The OE bushings are made from rubber and air pockets to provide a ride quality acceptable to a wide range of consumers. Unfortunately, the air pockets, coupled with the soft bushing material, produce excessive lower control arm movement in anything more than casual driving.
To remedy this, BMR offers a Lower Control Arm Spherical Bushings kit (TCA045) that replaces the stock rubber bushing. Nearly all unwanted lower control arm movement is eliminated by the kit. It does so by linking the rear portion of the lower control arm to the cradle through a stable connection to transfer power instead of absorbing and releasing it unpredictably, thus reducing wheel hop and also increasing stability.
From the factory, the S550 comes with stamped steel toe rods with adjustment bolts that deflect under load and produce inconsistent alignment and handling characteristics. For builds developing over 800 horsepower, Aiken has a secret alignment recipe that includes BMR camber links (UCA762) and adjustable Toe Rods (TR005).
Designed for high-performance street use, drag racing, and road racing applications with sticky tires, the camber links and toe rods work together to fine-tune the rear toe settings.
Aikens alignment also calls for lockout plates, used to eliminate the factory eccentric adjustment bolts. Lockouts minimize the change and deflection from the eccentric slipping and changing the alignment, but allow all of the adjustments on the toe rod. Lockouts are also ideal for cars with more than stock horsepower levels or soft compound tires as they tend to push the limits of eccentric bolts in rear suspension systems.
For more information about your specific build or needs, check out BMR Suspension.