“It just makes the car feel so much tighter and weight transfers are so much easier, so naturally you can just lean harder everywhere!” – Leyton Clarke
One car we are extremely familiar with here at Suspension Secrets, is the 991 Porsche GT3RS. Last year, we spent months at the track perfecting our suspension setup, using only the standard points of adjustment. On the Porsche GT cars, this is still quite an extensive amount of adjustment with the ride heights, anti roll bars, camber and toe all being adjustable from factory. Armed with our data logger, professional driver, and some of the finest machinery Porsche has to offer, we took to the circuits with RMA Track Days to put our setup to the test. We data logged every change to ensure that it was making an effect upon lap times and we recorded driver feedback from our super consistent test pilot and professional racer, Leyton Clarke. We ended the testing with some excellent setups for fast road use, track use and track use, using the Michelin Pilot Sport Cup 2 R tyre, which requires more aggressive settings to help use the superb grip on offer from these tyres.
With the testing complete and the standard adjustment pushed as far as possible, we went back to the drawing board to see what the next steps could be. We returned to the workshop with a GT3RS and began stripping the suspension down, 3D scanning the suspension, and CAD modelling the system to test the travel of the dampers, and the limitations of geometry. We were able to find some drawbacks to the system that could be improved by designing some bolt on replacement parts.
We noticed particular drawbacks within the front geometry, where the camber has a dead spot of adjustment that could be resolved within our top mount, and also found that more caster angle would be greatly beneficial to the performance of the car on circuit and on the road.
These two issues were solved by the complete re-designing of the top mount, and creating our own billet aluminium top mount with the improved geometry setting designed into it. Next, our attention was turned to the issue of the rear of the car becoming light under very heavy braking when out on circuit. This is partly due to the increased rake angle used in our setup that massively reduces corner-entry understeer. Therefore, we calculated a new spring rate for the front of the car that will maintain the handling dynamics through the corners, but will also keep the rear more stable under braking by preventing the nose of the car from dipping too far forward under heavy braking.
Another issue we have seen with these cars is when their ride height on the factory dampers is set to its lowest setting. This is a particularly popular setup choice in the U.S, but the suspension strut towers end up being damaged by the damper when it bottoms out over large bumps and compressions
Therefore, to avoid the possibility of this, we have re-designed the spring cups to work with the OE damper, but to re-set the damper ratio at the lower nose height. This sets the damper piston back to the OE position, but at the lower ride height, allowing you to benefit from the absolute best of both with the increased rake angle and full damper movement without running the risk of bottoming the damper out. Our spring cup also means that the damper travel works much more efficiently and sets the amount of front droop available, helping the car during turn in further helping to perfect get the grip ratio of the front and rear axle in the perfect position.
Finally, we turned our attention to the bump steer in the front wheels when the ride heights are altered from factory. Although the bump steer is minimal, we were designing the ultimate handling package for the Porsches, so wanted to ensure that the bump steer could be entirely removed from the system to reduce understeer further, and connect the steering to the driver to become much more intuitive, and to prevent the need to feed the steering lock on throughout the corner. The bump steer in the system as standard causes a slight sensation of understeer on corner entry as the car begins to load up the outside front wheel. As the car rolls onto the outer wheel, which compresses the damper, the bump steer occurs and causes the outer wheel to steer out from the corner slightly. This means that the driver is required to feed more steering lock as the car turns in. With the bump steer removed, the initial turn in doesn’t need to be adjusted on a constant radius corner, as the wheels will stay pointing in the direction that the driver has set.
With the parts CAD designed and 3D printed in house, we were able to test-fit our prototypes and check that the changes we intended within the design would work on the car, within the space provided, and also make sure that they work effectively with the remaining standard components. Once test-fitting was signed off, and a few more tweaks were made to the design to ensure fitment was perfect, we sent our files over to our machining partners in West Yorkshire to have all of our components machined to the absolute highest of standards, from aircraft-grade materials.
Once manufactured, we fitted the parts to our trusty test machine in the form of Leyton’s Porsche GT3RS Weissach and took the car down to the next RMA Track Day at Donington Park. With the parts installed and fully setup, Leyton headed out to do a few easy laps to check over the components and report back on any differences noticed, initially. However, it became obvious after he flew past the pit wall at full speed for the 10th time, that he must be enjoying the changes considerably as he couldn’t quite bring himself to come back off the track! Upon his return into the pits the feedback was very informative. The main feedback was:
“The car feels transformed. It was already great before, but now it is incredible. The stability through the corner is unreal and I’m now able to brake so much later and harder, whilst maintaining the car’s stability with no problems. The steering feels more connected and I’m no longer feeding on more lock as I head towards the apex. I can now turn in and hold the angle of the wheel through the entire corner. Mid corner grip is also improved, and speed is up substantially through the apex in slow and fast corners.” – Leyton Clarke
With the feedback logged, we checked the time splits and were thrilled with a great result of a two second reduction in lap times around Donington Park. This was a huge improvement over our previous setup, now that our parts had been fitted. The car was then sent out for the rest of the day at maximum attack to put the parts though their paces. With no issues, and a very happy driver, the car was checked over and ready for Silverstone two days later. Once again, the feedback was the same with only a rear wing angle alteration for higher speeds of Silverstone. Again, major time improvements could be seen, with cornering speeds up substantially, and a further three seconds were knocked off on previous times in the same conditions, tyres and driver around Silverstone, with our parts installed. After another full day of pounding lap after lap, we were able to fully sign off the Suspension Secrets Circuit Handling Pack with testing complete.
“This setup is unreal. This is the closest to a racing car, in terms of feeling and setup, that I’ve ever experienced in a road car.” – Leyton Clarke
Get in touch to discuss our pack for your Porsche GT. We have manufactured handling packs for the Porsche 991 GT3, GT3RS, GT2RS and Cayman GT4. Get in touch via our contact page to discuss purchasing and having yours installed soon!
Or click on the image below to purchase your kit now!
The full kit comprises of:
- New Billet Camber/Caster adjusted Top Mounts
- New Altered Spring Rate Front Springs
- Billet Damper Ratio Altering Spring Cups
- Bump Steer Tie Rod Ends
- Rear Camber Shims