Project S550 Part 2: Addressing Shortcomings in the Suspension and Drivetrain


You can see how the K-Member brace ties in the lower control arms and the frame rails.

The last set of mods we’ll cover in this update are focused on addressing the wheel hop we’re experiencing during hard launches. We started by installing the IRS subframe bushing support system– a group of aluminum bushings that sandwich the stock IRS subframe bushings in order to to dramatically firm up the rubbery mounts. Much like the voids around the transmission mount, the rear differential bushings also have large gaps that allow for unwanted movement in the IRS mounts. And again, as with the transmission, we solved the issue with polyurethane bushing inserts that help solidify these mounting points. These two relatively simple solutions are very effective at eliminating the wheel hop ithout creating any additional unwanted NVH. As we’ve mentioned, this is still a daily driver project, so NVH is an important factor at this stage of our project. While we had the subframe bolts out, we also installed an IRS subframe alignment kit. Many S550 owners have reported their rear IRS cradles being terribly misaligned from the factory. Luckily, ours was perfect and the alignment kit simply slid into place. Others have not been so lucky and have had to fight pretty hard to get everything aligned properly when installing this component. Lastly, we installed IRS subframe braces. This brace ties in the rocker panel, the front IRS cradle mount and the lower control arm mount in order to further limit any unwanted IRS subframe movement. So far, this combination of parts has done wonders in addressing the wheel hop issues, as it’s all but gone. We’re now at the mercy of the terrible stock tires, but we’ll take care of that soon enough.


Here’s what’s included in the subframe bushing support system kit. These billet components sandwich the stock rubber IRS subframe mounts providing a much more solid mount.
Here’s a break down of what’s included in the kit. There are two different bushing compounds depending on the stiffness desired; we chose the stiffer of the two to install on Project S550.

These are delrin sleevs that slide into the subframe bolt holes helping to ensure the IRS cradle is perfectly aligned. A simple, but effective way to ensure the IRS cradle is properly aligned.
Here is the design of the rear subframe braces. You can see the three mounting areas that tie in the rocker panel, the front IRS mount and the rear control arm mount.

Looking forward to the next update, we’ll focus more on the exterior and physical looks of the car as we transform Project S550 into a classic but aggressive build that will help to set us apart from other Mustangs in the parking lot.


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