In this blog, we’ll reveal the suspension upgrades needed to turn your road-going Porsche 991 GT3 RS into a rival to the Cup track car.
Capable of a sub 7-minute lap time around the Nürburgring Nordschleife, Porsche’s 991-generation GT3 RS is unquestionably ballistic. Packing up to 520hp, rear-wheel steering, massive aero and a lightning quick PDK transmission, this 911’s track credentials are surpassed by few other road cars.
And yet, park a GT3 RS next to a Cup race car and this 991 doesn’t seem quite so hardcore. Granted, Porsche Motorsport’s Cup version is slightly down on power (460-485hp), but it makes up for that deficit with more focused suspension comprising stiffer joints and more aggressive geometry. The Cup also boasts higher performing brake hardware and a cabin stripped of all unnecessaries to reduce kerb weight (dry weight is approximately 1,200kg versus around 1,420kg for the 3RS).
The great news for GT3 RS owners is that it’s entirely possible to achieve handling performance akin to a full-blown Cup car with bolt-on upgrades – and maintain usability on the road.
Read on to find out how…
Optimising Geometry: Camber & Caster
One of the most interesting – and important – differences between the GT3 RS and a GT3 Cup is the front axle geometry. The Cup car features more aggressive camber settings to maximise tyre contact patch through corners. Unfortunately for the GT3 RS, it’s not possible to achieve the same settings on the factory suspension.
Without enough negative camber dialled into the front axle, the outside tyre will roll onto its outer shoulder. This reduces grip and leading to overheating/excessive wear on the tyre’s edge. To achieve more track-oriented settings on a 991 GT3 RS road car, you’ll need Suspension Secrets Camber Caster Plate Top Mounts. These bolt-on upgrades are designed to provide the extra camber needed for serious circuit use. They also add caster.
Caster plays a major role in generating Cup car levels of steering feel. Increasing positive caster enhances steering weight and creates dynamic camber gain. This means the outside front wheel gains extra negative camber as the steering wheel is turned. This allows the car to generate even more cornering grip and means you can run slightly less static camber to maintain good straight-line braking stability.
For drivers chasing Cup car handling from their 991 GT3 RS, camber and caster form the foundation of improved cornering ability.
Correct Bump-Steer After Lowering
The 991 GT3 RS road car features ride height adjustment as standard. By lowering the car, you move its centre of gravity closer to the road, which enhances agility. However, lowering a car also changes the front suspension geometry and specifically the steering arms.
When the tie rod angle is moved outside the correct window, the front wheels can toe in or toe out as the suspension moves through bump and droop. This is bump-steer. On track, bump-steer manifests as a vague feeling on turn-in, or sudden understeer that causes the front wheels to wash wide of the corner apex.
The Suspension Secrets Adjustable Bump Steer Tie Rod Ends for the Porsche 991 GT3 RS are designed to solve this problem. These upgrade parts allow the steering arm position to be corrected after the car’s ride height is lowered.
This is one of the most Cup car-like upgrades you can make because it improves how the 3RS follows a steering input. On corner entry, you’ll notice a cleaner and less disruptive response from the chassis as the steering wheel is turned. This boosts driver confidence and ultimately leads to more consistent lap times.
Add Spring Rate to Control the Extra Grip
The upgrades described above will make the tyres work harder and more effectively. However, this means the chassis must deal with increased loads.
After optimising suspension geometry and/or fitting grippier tyres, body movements can increase and make the car feel softer overall. Increasing grip levels increases lateral forces, which means more rolling and pitching from the body. At this point, it’s important to increase the spring rate and improve body control.
The Suspension Secrets Circuit Handling Pack for the Porsche 991 GT3 RS is a complete front end solution. It includes camber plates, bump-steer tie rod ends and – crucially – uprated Eibach springs with spring cups to improve body composure. Combined, these parts sharpen front axle response, reduce understeer, improve braking stability, and increase mid-corner grip.
These upgrades move a 991 GT3 RS much closer to a Cup car in terms of handling performance. And that’s before an aftermarket damper solution is considered.
Upgrade to Track-Focused Coilovers
Standard 991 GT3 Cup suspension is unsurprisingly focused on track performance. However, aftermarket coilovers for road cars like the GT3 RS actually offer more damper adjustability. (This is why Hinz Motorsport’s Cup car is equipped with an Öhlins TTX system. Read more about that car later in the article.)
For owners searching for a whole new level of handling performance, coilovers are the next step. The Suspension Secrets 991 GT3 RS coilovers range includes three-way adjustable KW V4 Clubsport and Nitron R3 coilovers.
The advantage of premium coilovers is their range of adjustability. You can fine-tune ride height, damping, kerb behaviour, front-to-rear balance and body control. This becomes especially important as tyre grip increases and the car starts demanding more support from the suspension.
On 3-way coilovers, it’s possible to adjust high and low speed compression, plus rebound. A properly set up coilover package can make the GT3 RS more stable under braking, more precise on turn-in and more composed through fast direction changes. All while soaking up kerbs and surface imperfections more effectively.
Remove Axle Deflection with Monoballs and Solid Bushes
Another significant difference between a GT3 Cup and the 991.1 GT3 RS road car is that the race car uses solid spherical joints rather than compliant rubber bushes.
Rubber bushes are used to reduce noise, vibration and harshness on road cars. However, these bushes flex during hard driving, negatively affecting suspension geometry and reducing handling consistency. This problem is exacerbated as the car ages and the rubber perishes.
Porsche tackled this issue on the succeeding 991.2 and 992-generation GT3 RS by fitting solid monoballs on the front and rear axles. The good news is that you can replicate this setup on the 991.1 and, in the process, mirror the Cup car with the Suspension Secrets Rear Upper Control Arm Monoball Kit plus Solid Control Arm Bushes for the front axle.
This package removes unwanted compliance in the suspension system and generates more consistent grip on track. Once equipped with solid monoballs, the 991.1 GT3 RS will feel more keyed into the track surface, and the more stable geometry will give the driver the confidence to take corners at greater speeds.
Fine-Tune Camber with Shims
A Cup car setup is precise by design. Minor adjustments made to camber, toe, rake and ride height can dramatically change chassis balance. Camber shim kits for the 991 GT3 RS are a useful way to achieve Cup levels of setting accuracy and ensure maximum tyre contact with the track surface.
The Suspension Secrets Front Camber Shim Kit and Rear Camber Shim Kit help achieve optimum alignment settings for track driving. This is particularly important if the car is running semi slick or slick tyres, a lower ride height and/or other upgraded suspension components.
Best Upgrade Path for a 991 GT3 RS
So to recap, here’s the route you should take if you want to get your Porsche 991 GT3 RS handling more like a Cup race car…
- Start with camber, caster and bump-steer correction.
- Add spring rate and damper support to control the extra grip.
- Remove unwanted rubber bush compliance with monoballs.
- Fine-tune alignment with camber shims.
- Match the setup to the tyre, circuit and driver.
Follow this step-by-step guide and your 991 GT3 RS will turn in harder, hold its cornering line more accurately, and provide the extra feedback required for achieving not just new personal best lap times, but more consistent lap times as well.
Hinz Motorsport’s GT3 Cup
During a recent visit to the USA, Suspension Secrets parts stockist Hinz Motorsport was kind enough to give us seat time in its awesome 991.1 GT3 Cup car. Company founder and Porsche nut Rick Hinz has equipped this Cup with Öhlins TTX dampers for additional adjustability over the stock setup.
Find out what we thought of Hinz Motorsport’s GT3 Cup in the video linked here. You can also watch our full episode on how a GT3 Cup differs from a GT3 RS here.
