In my mind, there are four stages of suspension upgrades:
- Stage 1: one or two bolt on parts
- Stage 2: a cohesive group of bolt on parts
- Stage 3: a more extreme cohesive group of bolt on parts
- Stage 4: a custom reworking of the suspension
Many car manufacturers sell cars in these stages such as Ford with the Mustang and Chevrolet with the Camaro. A perfect example is the Porsche 911: 911 S, 911 GTS, 911 GT3, and 911 Cup Car. This isn’t going to be a technical overview on suspension geometry and tuning, but I will explain the importance of replacing parts with a purpose. I am going to focus on performance suspensions so I won’t be covering non-performance modifications like air suspension or “stancing”. The goal is to have a suspension setup that works together as a complete and balanced system.
The first stage addresses one or two glaring weakness in the setup of the vehicle. A great example of this is adding sway bars to the new ND Miata which suffers from terrible body roll; adding sway bars greatly reduces that roll with just a single modification. Grassroots Motorsports recently did just this for a noticeable drop in lap times. Another more general example is installing lowering springs. As long as the drop is not too far, the center of gravity and roll center should be lowered for better handling, and most lowering springs are stiffer than the stock springs.
This is how most people start modifying their suspension, and in moderation, there is nothing wrong with it. I first started with Tein S Tech lowering springs and Eibach sway bars. The car handled better and remained within proper spec.
This is a more holistic approach to modifying the suspension: struts, springs, bushings, sway bars, and a performance oriented alignment. The limiting points to this stage is the roll center, bump steer, camber, and toe. If the car is lowered too far, the roll center will be raised, bump steer will increase, camber will be too negative, and/or toe will be too extreme. If the springs and struts are too stiff, then the car will struggle on all but the smoothest tarmac. If the bushings are too stiff, then the driving experience will be very unpleasant.
This is the stage I am currently at. My springs and struts are stiffer and 19mm shorter. My polyurethane bushings offer less flex than rubber but more compliance than Delrin or aluminum. I have my sway bars set up for my car’s specific setup, and my alignment is more sport oriented than factory settings.
This takes Stage 2 to the next level with more track-oriented parts: coilovers, adjustable suspension arms, and a more aggressive alignment. At this point, the only limiting factors are budget and suspension design. The coilovers can be tuned to the needs of the car for both spring rate, damping, and height; the car can also be corner balanced. Once the height is set, the adjustable suspension arms can set camber, caster, and toe to the desired performance settings. Likely a serious build at this point, Delrin and solid bushings are tolerable for their performance gains. For solid axle cars, a Watts link would be a big upgrade in this stage.
I plan to have a Stage 3 set up once the car is a dedicated track car. The car will be lowered an additional 12mm with stiffer struts, springs, and bushings. The alignment will have more negative camber, slight toe out, and a bit less positive caster. This is the furthest most people go with their car.
It’s a dedicated race car. Suspension pick-up points are moved, subframes are replaced with DOM tubing, and everything is endlessly adjustable. I have no intention of ever going this far with a car. If you plan on it, you’ll want better advice than I can provide, but I can tell you it will be expensive and complicated.
But, which one?
Be honest with yourself: as awesome as having a race car on the street sounds, it will stop being fun pretty quickly. Additionally, the price increase with each stage is substantial and may not be worth it; even a simple suspension can be a blast on the track. If you drive the car everyday, really the most extreme you should go is a Stage 2 or mild Stage 3.
These aren’t concrete stages and don’t necessarily have to be done the way I have laid them out; my point is that a great suspension is more than the sum of its part. The best way to get around the track is with a well-balanced, holistic suspension, and the most extreme option won’t always make you faster. $3,000 coilovers are worthless if they cause massive toe-in and six degrees of negative camber; that money would be better spent building a more complete Stage 2 setup. So, choose wisely, and keep it balanced.