Something I haven't concerned myself with too much was my suspension system. The car handles so well from the factory I didn't want to mess with it. Not only did my car handle very well, but it rode very smoothly. The bumps in the road didn't hurt your back like the R1 and R2 packages. The only thing about the factory setup I wasn't happy with was the ugly wheel well gap. The car just sits up too high, especially in the back. This was my first motivation for doing some modifications to the stock suspension system. My other motivation was that I was beginning to find the limits of the stock suspensions setup. I was beginning to experience some body roll and was planning on doing some racing in the near future. I called around to a few performance shops and consulted the RX7 List for recommendations on lowering springs. Here are some of the things I found out.
There are two types of springs, progressive rate and linear rate. Progressive rate springs have a spring rate that changes as the spring is compressed. They have a soft spring rate under light load, during normal driving conditions. The spring rate increases as the load is increased. This is a good compromise for someone who wants a smooth ride with reduced body roll in turns. The linear springs are one rate regardless of load. Although the ride is not as comfortable as progressive springs, the linear springs are more consistent. Linear rates are more ideal for racing applications because of their predictability.
Most people go with the Eibach, Racing Beat, H&R, or PFS "comfort" lowering springs. The Eibachs are linear and lower the car about an inch. The H&Rs lower the cat about 1.5 inches and are also linear. PFS and Racing Beat have a progressive rate springs and I've heard rumors of the Racing Beat springs sagging over time. These lower the car approximately one inch.
I was concerned about what the car was going to look like with the aftermarket springs in place. I wanted the car to look a certain way. Once the springs are in place, that's the way the car is going to be and there's no way of making any adjustments to them. The only way to get full adjustment over ride height is by going with adjustable coil overs. After talking with others, I found out that the "drop in" springs mentioned above really aren't that much stiffer than the stock springs. The performance gain is minimal and they are mainly for looks. Most people that start out with "drop in" springs usually end up going with adjustable coil-overs down the road. Although adjustable coil-overs are a bit more expensive, I'd rather do it right the first time then to put in a set of springs I'm not going to be happy with shortly after. Besides, I was planning on getting into some racing anyway...... coil-overs it is!
Deciding on which coil over setup to go with was easy for me. I'd been hearing so many good things about the Ground Control setup I had to check them out. I gave them a call and talked to them about what I was going to be using my car for. I told them I would be into some auto-crossing and possibly some road racing. They set me up with 500 ft lbs (front) and 400 ft lbs (rear) Eibach linear rate springs. At first I was a bit concerned about what the ride was going to be like, but to get the performance I wanted I was going to hjave to sacrifice some comfort.
My next concern was shocks. Ground Control has their own brand of racing shocks they sell at a mere $400 each! Needless to say, that was a little over my budget. The next best thing on the market is the GAB Super R's. These are the shocks I really wanted to go with but unfortunately they have since been discontinued. There are a few still out there, but at $850 a set, I felt they were a bit costly. Next I looked at the Konis and Tokico Illuminas. I was told by Ground Control that the Tokicos would not provide enough dampening for the spring rates I had. Koni's would work, but they were marginal. I later found out that the Koni's could be revalved for my spring rates and even be converted to double adjustable for $240 per set. I was lucky enough to bye a set used with only 3000 miles on them. Since my intentions were to get them revalved, it didn't really matter to me if they were used. The amount of money I saved made it well worth it.
When the coil-overs were finally installed, I started out by lowering the car. I acquired the best look for the car when all four fender wells stood 24.75 inches from the ground. I waited a week or so before I got my car realigned and boy did it wear the inside of my tires! They need to be replaced soon anyway so I didn't worry too much about it. If you ever have your car lowered, get your car aligned immediately.
The Konis were set at 1/4 turn back from firm for the front and1/2 turn back from firm on the rear. On the first day of driving I noticed that the car rode very firm and I had a sore back because of it. Since then I changed the front settings to 1 turn back from firm and the backs 1.25 turns back from firm. These settings are relatively comfortable for street use because my sore back went away. Either way, body roll was reduced and the car feels more predictable in turns.
With the car set as low as it is I've been having some problems with bottoming out when I speed over big dips in the road. I can't figure out whether it's the car or the supension bottoming out. Either way I need to be careful. I thought the increased springs rates would be enough to stop the car from compressing enough to bottom out, but I guess I was wrong.
It's been about two months since my coil-overs have been installed. After foolling around with the adjustments on the Konis and racing in a few autocrosses I came to realize that the car handles the best with the shocks set at full firm. The car bottoms out less and is much tighter in turns with the shocks all the way firm. My back has gotten used to the rock solid suspension and I've been doing most of my driving with the shocks cranked all the way up. I still bottom out more than I'd like, so I raised the car two turns on the collar. This equates to approximately 1/4 inch. We'll see how the car reacts to the adjustment.
The purpose of sway bars is to reduce the body roll of the car in turns. The stiffer the sway bars, the less independent each wheel is from the other. Sway bars are also a good way of correcting any over steer or under steer characteristics in a car's handling. A general rule of thumb is stiffer in the front creates under steer and stiffer in the back creates over steer. they also prevent the suspension from swaying while the car is turning. The 93 rx7s have a tendency to over steer. Putting a larger sway bar up front will cause the front tires to sway less which reduces grip of these tires. I purchased a complete set of used Eibach sway bars in an attempt to reduce body roll. I never felt my car had an over steer problem. The handling is very neutral in turns when speed remains constant. If I were to accelerate in a turn the car over steers tremendously. This is known as throttle over steer, which is very common with high horse power rear wheel drive vehicles. The Eibach front sway bar is considerably bigger than the stock front sway bar. The Eibach rear sway bar is roughly the same diameter then the stock rear sway bar but has two different adjustment settings. Both front and rear Eibach sway bars are stiffer than the stock sway bars due to their more solid construction. I installed both sway bars and set the rear to the softest setting or the outer most holes.
Strut Tower Bar