Over the last 5 years, I’ve worked closely with Dodson Performance and used their products on many of my race and street cars. When building the RX7, we chose to use their HSD suspension and it has worked very well over the last 3 years, providing a low ride height and great performance on the track. While there was nothing wrong with our previous setup, with the constant progression of drifting we are always looking to improve the car and it’s handling characteristics. So the decision was made this year to switch to another brand of suspension also available from Dodsons: OZ Racing Suspension.
Eastern Automotive was kind enough to let me use their hoist and corner weights to install and setup the new suspension. Here you can see the new OZ Racing (silver and black) versus the old HSD (green and black).
After setting the suspension to the height I wanted, we dropped the car on the corner weight scales to try and get equal weight on all four corners. This is something that in my mind is extremely important when setting up a car if you want the suspension to work correctly. Having each strut sitting at the same point in the stroke means you will be getting equal spring and dampening force from each corner of the vehicle.
To test the car, I headed to the familiar Hampton Downs circuit, where DMNZ was holding an open day. All alignment settings and tyre pressures were being kept the same from the last time I drove at Hampton, with the only change being the new suspension. Initially, I had the dampening set 4 points from full soft front and rear. I quickly discovered that the OZ Racing rear struts have a fair bit more travel than the HSD I was previously running, allowing the car to utilise the full stroke without hitting bumpstops. Even with the car 20mm higher in the rear, it will still touch the sideskirts to the ground under compression!
As I don’t run swaybars front or rear, I can really feel what is happening at every corner of the car. The extra stroke from the new suspension instantly translated into more forward bite. I had to come in after only a few laps to increase the rear dampening and re-adjust tyre pressures.
The other thing I noticed, was the front end didnt seem to roll around as much as before, but the dampening in the front almost seemed lesser? I can only assume this is from a shorter, heavier spring, combined with softer valving. I upped the dampening by a large amount through the next two sessions, finding a point that I was happy with. With the front end roll reduced, it has helped to keep the rear of the car more equally planted without the use of swaybars.
At the end of the day’s testing, I had only changed dampening settings and tyre pressures. The car is now sitting at 6 notches from full hard in the front and 4 notches from full hard in the rear. Versus my last HSD setting from Hampton Downs which was full hard in the front and 4 notches from full soft in the rear. What this has left me with is a setup where I can still tune more softness in to the rear, and I have a front end that is now better suited to running with no swaybar. While the HSD are a great suspension package, I think these new OZ Racing coilovers suit my car and driving a bit better for what I’m using it for.
I really can’t wait to run the rest of the season with the new suspension, and hopefully I’ll be able to change a few alignment settings etc to further improve the car.
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