Project FR-S: More Rear Suspension with Cusco and Whiteline
In our last segment we brought the front suspension of our FR-S up to the latest top standards with new parts developed for the car since we started developing our project. Now it's time to bring the rear suspension up to snuff with some of the latest parts now out for the car. Since we started out project, Cusco and Whiteline have come up with more parts for the rear suspension.
Our suspension had first gotten done well over a year ago and we used Suabaru STI parts in the initial stage. We used Cusco adjustable lower arms and some Whiteline bushings and their first generation of rear swaybar. As we are running tires much bigger than stock, (265 vs 215), the additional grip was causing a lot of body roll even with our KW coilovers and upsized swaybar.
With only the lower arm adjustable we could not reduce our negative camber as much as we wanted to and we still had a bunch of squishy rubber bushings in the back of the car. Now that Cusco and Whiteline have come out with more parts it was time for us to get installing again.
We already had the Cusco lower rear control arm but to eliminate some rubber and add some adjustability in the toe curve we added Cusco's traction link that replaces the stock part. Making this link shorter gives more toe in under roll, making it longer reduces the toe in under roll. We made the link slightly longer to reduce toe in under roll.
We also installed Cusco's toe links for toe adjustability. With the use of these links we could lock out the stock toe adjusting eccentrics. With spherical bearing replacing rubber the toe is controlled more accurately under hard side load. You can really feel rear toe changes when driving hard. Most drivers can feel 1/8″ of an inch change so it's important to reduce deflection here.
Whiteline has come up with a larger adjustable X-Blade rear bar for the FR-S (part number BSR54XZ)
than what we previously ran. It is 18mm thick vs the 16mm thick part we had before. This is much better than the stock 14mm part with is nearly useless. The new bar is approximately 60% stiffer than the old part and a whopping 170% stiffer than stock. This gain gives around a 30% overall increase in rear roll stiffness. The X-Blade rear swaybar comes with Whiteline's new ball joint adjustable swaybar links, positioning collars and braces that secure the chassis mounts to the crossmember so they won't tear out. Having adjustable end links is important to take the preload out of the bar when corner weighting.
Previously we had added Whiteline's subframe bushings (part number KDT921)
that filled the gaps in the rubber mounts with urethane. Although these helped reduce subframe movement greatly, there was still a bunch of soft rubber back there. To get rid of the rubber we opted to completely replace the bushings with Whiteline's urethane parts to get rid of more compliance.