We took our Porsche 718 Cayman GT4 fitted with Suspension Secrets Circuit Handling Pack to Spa to hunt down a 992 GT3 RS running Suspension Secrets front camber blocks.
There are circuits, and then there is Spa-Francorchamps. A temple of speed, gradient and concrete walls, it is where myths are made and weaknesses exposed. It’s no surprise then, that we chose Spa as the stage for the ultimate comparison: our fully upgraded Porsche 718 Cayman GT4 versus the formidable 992 GT3 RS – a car widely considered the zenith of Porsche’s track-focused lineup.
But this wasn’t just a David versus Goliath spectacle. This was a study in suspension sophistication versus aerodynamic dominance. Our Cayman GT4 has undergone an exhaustive transformation through the Suspension Secrets Kinematics Kit, targeting every link and angle of its underpinnings. The question: can chassis geometry and mechanical grip close the gap to the GT3 RS’s downforce-led supremacy?
GT4 Suspension Upgrade
Our Cayman GT4 began its life as any other from Stuttgart – well-balanced, capable, and planted. But to push its limits, we replaced good with extraordinary. Our GT4 Circuit Handling Pack Kinematics Kit forms the backbone of our chassis transformation. This includes upgraded top mounts offering increased camber and caster, rear camber shims, bespoke toe arms, and bump-steer tie rod ends. Crucially, we’ve also fitted adjustable spring cups to finely manage bump-to-droop ratios giving us the freedom to run the car significantly lower without upsetting the dampers’ operation window.
The goal here wasn’t simply to sharpen turn-in or reduce body roll; it was to make the car behave like a true racing platform, with maximised tyre contact patch control across all dynamic states. Every degree of camber, every millimetre of toe, was calibrated to extract stability at high speeds and responsiveness at the apex.
To match the chassis, power delivery was refined. Genome Design provided the engine calibration and over-axle pipes with OPF delete, freeing up low-end torque – critical in a manual transmission car like the GT4. Braking was upgraded via factory-fitted carbon ceramics now paired with Pagid RSC1 pads, delivering excellent modulation and fade resistance on long track sessions.
Still, this was a road-based GT4 taken to its engineering edge. The question remained – how would it fare against the GT3 RS?
Cayman GT4 Circuit Handling Pack Kinematics Kit (718/981)
What is included:
- Suspension Secrets top mounts with increased camber and caster
- Upgraded front and rear Eibach racing springs with increased (stiffer) spring rate with front helper springs
- Suspension Secrets spring cups which help retain the compliancy of the damper even after the car has been lowered
- Suspension Secrets bump-steer tie rod ends which help to remove unwanted bump-steer
- Suspension Secrets adjustable rear toe arms
- Suspension Secrets camber shim kit
992 GT3 RS Front Camber Blocks
Lined up next to us was Leyton Clarke’s 992 GT3 RS, howeverthis wasn’t a showroom RS. As Managing Director of RMA Track Days, Leyton’s car is a showcase of trackday optimisation. It runs Suspension Secrets GT3 RS front camber blocks (pictured below) and an aggressive track-spec setup, including Michelin Cup 2 R tyres and the JCR Developments aero kit, adding front canards, rear endplates, and a Gurney flap. These partsmagnify an already immense downforce package.
992 GT3 RS camber blocks benefits:
- Increased front axle grip
- Improved steering feel
- Reduced tyre wear
- Greatly reduced understeer
- Increased cornering speed on the road and track
- Very easy to install
To put it bluntly: this was a GT3 RS on another level. If our GT4 was to get close, it would be down to precision not power.
Data Doesn’t Lie
With VBOX systems fitted to both cars, we could do more than rely on seat-of-the-pants impressions. We could quantify every gain and gap. As expected, Spa’s high-speed nature played to the RS’s strengths. The most staggering data came in braking zones. At the end of the Kemmel Straight, the GT3 RS scrubbed speed with shocking efficiency, braking a full 50m later than the GT4 while carrying over 30mph more into the zone. The longitudinal G-force disparity on the graph told the story: aero braking.
This was the RS’s party trick – 800kg of downforce at 180mph, translating into mechanical grip and near-telepathic braking response. Even with carbon ceramics, the GT4 simply couldn’t match the confidence or efficiency with which the RS slowed from triple-digit speeds.
However, the mid-corner analysis painted a more flattering picture of the GT4. In corners like Bruxelles and La Source, where speeds are lower and aero less relevant, the GT4’s upgraded suspension shone. The car rotated cleanly, with the suspension kit helping maintain ideal camber through loaded corners. According to Leyton, in these scenarios the Cayman GT4 Kinematics Kit was “surprisingly close” in feel – particularly as both cars rely primarily on mechanical grip at sub-100mph speeds.
Increased Mechanical Grip
What this experiment ultimately confirmed is that while the GT3 RS dominates via aero and rubber – those massive 275/335 Cup 2 R tyres making a considerable contribution – the GT4 Kinematics Kit closed the gap significantly where aerodynamic downforce is less dominant.
More telling was the GT4’s composure. Its revised geometry allowed better use of its narrower tyres. The improved bump/droop balance, camber control, and toe stability meant that in transitions and technical segments, the GT4 retained poise and allowed earlier throttle application – traits typically reserved for mid-tier racing cars.
The GT3 RS still pulled ahead, but the differential wasn’t always about power – it was grip and braking efficiency. And in sectors where geometry rules over wings, the GT4 held its own.
The Spa Experience
While we left Spa in awe of the GT3 RS’s capabilities, we also came away with proof of just how potent a properly engineered suspension setup can be. There’s no denying that to close the final seconds, we’ll need to look at three areas: aero, tyre width, and compound. The GT4’s next chapter will involve increasing its contact patch and bolting on meaningful downforce, all while preserving its balance and usability.
Power? That’s less of a concern. With the current engine tune delivering 484hp, the GT4 already feels powerful, especially in UK circuits where average speeds are lower. In fact, we expect the delta between both cars to shrink dramatically at tracks like Donington or Brands Hatch, where downforce matters less and suspension matters more.
Porsche Cayman GT4 Kinematics Kit – Final Thoughts
This wasn’t just a showdown between two Porsches – it was an exercise in how much suspension kinematics can transform a platform. The 718 Cayman GT4, with its meticulously tuned geometry, managed to flirt with the RS’s shadow – not by outpowering it, but by out-thinking it mechanically. Around one of the world’s toughest race circuits, our GT4 Kinematics Kit more than proved its worth.
Yes, the GT3 RS is still king of the circuit. But what we proved at Spa is that with the right chassis tuning, a Cayman can punch far above its weight. Our Circuit Handling Pack-equipped GT4’s lap time of 2mins 41.67secs with cold rear tyres and traffic is proof of that.
See PORSCHE Suspension Secrets upgrades here.
