We freshened up our FD’s30-year old, worn out suspension bushings with SuperPro USA polyurethane bushings and replaced the clunking old pillow ball bushings in the rear suspension. We also vapor blasted the aluminum arms and powder coated the front subframe to match the rear.
While we were upgrading the differential in Part-16, we decided to replace the worn-out bushings in our FD’s control arms. The FD RX-7’s suspension is extremely impressive and has some of the least stiction (or binding) of the suspension of any car I have ever seen. Once the damper is unbolted, the suspension upright and arms fall down with very little resistance or binding of bushings. Normally, rubber bushings provide a lot of stiction and hold the suspension at the ride height that the bushings were tightened to. This affects not only ride quality, but the spring rate and the damper’s effect on controlling the suspension.
A big part of this lack of stiction is Mazda’s use of pillowball bushings (aka: Spherical bearings) in the upper and lower control arms. Mazda uses six in total with one on the outer upper control arm, and two on the lower control arm. These pillowballs are also prone to wearing out and creating slop, and a corresponding ‘clunk’ in the suspension when starting and stopping. Our FD exhibited this clunking from the rear and new pillowballs were in order.
For the non-pillowball bushings, we turned to SuperPro USA for their unique polyurethane bushings that have their patented elastomers, resins, and curing agents that give their bushings the performance and attributes that has made them so well-respected in the industry due to a lack of Noise, Vibration, and Harshness (NVH) and squeaking that often comes with lower quality polyurethane bushings.
In Part-3, we used SuperPro USA’s steering rack bushings and SuperPro Front Swaybar to reduce body roll and slop in the steering rack of our car. We are big fans of SuperPro USA and have used their bushings in many applications over the years. These bushings hit the perfect balance of improving performance without compromising the ride quality for daily drivers, performance cars, and competition cars. I was looking forward to the improved handling and ride quality that I’ve come to expect and enjoy from their products.
The lower lateral control arm features a pillowball bushing (spherical bearing) on the outer attachment to the upright, as well as the center bushing that connects to the trailing link. This trailing link center bearing was the main source of our particular clunk.
Since the lower arms are the most visible, we decided to clean up the casting marks to make the arms smoother and look a little better.
5 comments
I dig that clamp designed into the sway bar mount, very cool! Loving this build, almost a roller!
What is the overall goal for this car, Billy? You are putting so much money into it that you might never drive it to avoid scratches! Everything is top notch and I enjoy reading every installment.
The car is being built to be driven and to share the rotary platform to a new group of people and to demonstrate that with proper engineering, they can be reliable and extremely high performers. The car will be tracked and taken to many events. This is not going to be a show car or garage queen.
It is done as a well balanced reliable car and this and what we did to our STI are examples of what it takes to do it right.
Amazing job on the bushing work who did that for you