The Importance of Proper Suspension Setup

Uncategorized | December 05, 2016

Here at DirtFish, we receive quite a few questions about the car setup we use each day in our driving programs. Whether it’s the suspension we use, modifications to the engine, brakes, or even the material we choose to protect the underbody, everything has a purpose.

By far one of the most important modifications we make to all of our cars is the suspension. After all, it is what keeps the tires in contact with the road. Over the years, automotive companies like Subaru, have made massive technological improvements to suspension and the way it functions. There is a noticeable difference between the equipment that is fitted to today’s cars even compared to cars from five years ago. Some companies will even go as far as changing the suspension between years that fall within the same generation of car.

On the DirtFish school cars, we have used everything from the suspension that comes on the cars out of the factory, to beefier struts, all the way up to some of the best rally suspension in the world. There are multiple factors we take into consideration while deciding which setup to use. When making that decision, it comes down to two major factors: it has to work well for the techniques we teach and use at DirtFish, and two, it has to be able to reliably work 6-7 days per week in multiple conditions and surfaces all year long. Nobody uses cars quite like we do… Yes, competition rally cars see similar roads and conditions (sometimes even worse), but they do it for a couple of days every 3-4 weeks, not every day throughout the year. We want our customers to have the best experience possible and give them the tools needed to become better, more confident drivers.

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On this fine overcast Pacific Northwest day, our shop has set us up with one Subaru BRZ that is equipped with OEM suspension, and another with the same rally suspension we use on all of the STI and BRZ school cars at DirtFish. One of the most important aspects of suspension in the sport of rally is the strength of the components. Most OEM suspension is built to handle everyday driving on (mostly) smooth paved roads. Rally suspension needs to be able to withstand the brutal conditions found on a rally stage – loose gravel, acceleration and braking bumps, massive potholes, softball-sized rocks, boulders embedded in the road and so on. Rallies aren’t usually held on the smooth, well-maintained roads we drive on. Because of this, everything is strengthened from the strut housing and pistons to the spring seats and mounting hardware. Everything is constructed to be much stronger and more durable, simply because it has to be. All of this will inevitably add weight, but weight won’t matter much if you aren’t able to finish due to a bent strut or failure in components. In addition to the stronger components, a larger strut housing allows more room for additional fluid. This means it will take more use before the struts overheat and begin to bottom-out more easily.

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The rally suspension we have mounted is a proper rally setup. The front is equipped with a Reiger Racing Suspension coilover and the rear with a custom Bilstein coilover. Both have valving that is specially made to perform best under conditions that we see at DirtFish on a day-to-day basis. Both the compression and rebound are firm, meaning it takes more force to compress the spring and strut, then they re-extend faster as the weight is moved off of them. Combined, this forces the tires harder into the ground giving them a stronger contact with the gravel below, ultimately giving the driver more control.

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To find out how important and different a proper suspension really is, Instructor Michelle Miller and I spent some time behind the wheel of two identical DirtFish Subaru BRZ school cars – one with OEM suspension and the other with the up-rated rally suspension. At DirtFish, we are lucky enough to have everything we need to accommodate tests like this one. We have well maintained roads, identical cars, and the best mechanic shop that is constantly keeping our fleet in top shape for our customers and drivers.

Before we got started, we took a couple of measurements to get an idea of the difference between the amount of suspension travel each car has. Both cars had identical lengths of travel in the rear, so this is one of the aspects where valving will really come into play. The front was a different story. The rally suspension showed an increase of two inches over OEM. To most people, two inches doesn’t seem like much. However, when it comes to rally and using weight-transfer techniques, that is two more inches you are allowing your car to move around while still pressing the tires into the ground. This gives you more traction and ultimately more control of the car.

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The main areas of focus for Michelle and I with both cars were:

  1. How does it react under braking/acceleration?
  2. What are the differences between the two when it comes to lift-off oversteer, lift-turn-brake, trail brake, pendulum turns and throttle steer?
  3. How does each car handle different types of bumps (large and small) in the road?

The course of choice for this test was the Boneyard, which is a great controlled and consistent environment to feel the differences in two nearly identical cars. The Boneyard features five corners with varying degrees of difficulty – long fast corners, off-camber corners and tight, low-speed hairpins.

We started on the pavement and accelerated down the long straightaway into the first tight lefthander, trail braking and scrubbing speed prior to entering the corner. Through this corner, I was able to feel an immediate difference between the two setups. With the OEM suspension, I had less control of the initial rotation and when it would happen; it took a bit more work to control the car through the corner and maintain my momentum. The rally suspension was a very different story – while trail braking, it required me to be more aggressive, but I was able to feel the movement of the car much more, making it much easier to adjust my brake pressure accordingly for the corner. Once I was back on the power, I could feel the car squat hard on the rear, giving me more traction to help accelerate out of the corner.

Exiting the first corner, I straighten the car out and accelerated for corner number two. For this corner, I use the lift-turn-brake technique – lifting off of the gas and lightly applying the brake to rotate the car and again, easing into the throttle to maintain the rotation and momentum. As with the previous corner, the BRZ with the OEM suspension rotated very quickly with little control, so it required me to be ready to counter steer early, but then be gentle with the throttle. If I correctly timed the braking with the rally suspension, I was able to feel more of the weight move from the rear of the car to the front outside tire. This helped begin a controlled rotation allowing me to place the nose of the car precisely where I want it and begin accelerating through the corner early.

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When I was able make it through corner number two well, I could stay on the throttle all the way through the long and fast third corner. On top of being the fastest corner on the course, it is also a rough corner with large “whoops” all the way through it. These “whoops” tend to throw the weight around, upsetting the car. This requires the driver to do a lot more work with the steering wheel and throttle to maintain the momentum. The Reiger/Bilstein setup made this corner unbelievably easy, absorbing the bumps without upsetting the car, allowing me to make minimal adjustments with the steering wheel and stay hard on the throttle and accelerate out of the corner. The OEM suspension did not handle this corner nearly as well. I was still able to stay on the throttle all the way around the corner, however it required larger steering inputs and a little bit less throttle. Obviously, less throttle means lower speed on the exit of the corner.

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Entering the fourth corner, I was carrying a good amount of speed at the top of second gear. This was one of the corners that required much more aggressive braking at the beginning of the turn to start the rotation, but it was pretty slippery mid-corner. So if I didn’t initiate a good rotation using the brakes early in the corner, understeer was inevitable. The improved feeling from the rally setup allowed me to rotate the car early and avoid understeer, while still keeping the weight on the front tires before easing back into the throttle and keeping my momentum moving through the corner. Out of the two runs with the stock suspension, I was only able to do the same thing once and the other time ended with me fighting the horrible understeer that I… I mean the suspension, had created.

If executed properly, the transition between turn four and five can be treated as a pendulum turn (Scandinavian Flick), carrying the momentum from turn four and using the brake to transition (flick) the car from one direction to the opposite. The stock setup required lighter, longer braking to make the direction change and with the aftermarket setup it was remarkably easy to change directions. All it took was a simple tap of the brakes and a slight countersteer in the other direction. That was probably the most fun aspect of the new suspension, just how quickly and easily you are able to change directions from one corner to the next.

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Michelle and I have fairly different driving styles, but we both had similar reactions to the comparison. First, the OEM suspension “…works well, but requires a lot of patience, gentleness and being very ahead of your car so that you are able to predict the inputs needed” said Michelle. Overall, the aftermarket suspension requires you to be a little more aggressive on corner entry, but also allows you to do less work once you’re in the corner and back on the power. Basically, it’s easier to keep the car on the intended line with less work. Michelle continued by saying, “You could feel how a slight manipulation of the brake pedal could change the dynamic of the vehicle, particularly on corner-entry as you are searching for grip and a good apex.”

Some people will tell you over and over why you should really spend money on upgrading your suspension, while others tell you not to worry about it and to just add more power. Prior to working on this article, I would have been one of those people telling you to add power. I do love a substantial amount of horsepower and enough torque to take me from zero to sixty in less than three seconds. Now that I have tested OEM and purpose-built rally suspension side-by-side, I would still tell you to add more power. However, I would also tell you to improve your suspension! That way you are able to really make use of all of that power and make it substantially easier to drive your car.

Article by: Trevor Wert (DirtFish)

Photos by: Justin Fitch (DirtFish)