Porsche’s Cayman GT4 is a wonderful car that is an absolute joy to drive. And that’s just it – it’s meant to be driven. There’s so much to love from a true driver’s perspective. Mid-engine platform, manual gearbox, its 3.8L NA flat-six engine that pushes 385hp from the crank. It really is one of our favorite Porsches. However, it does have a few shortcomings as you begin to push its limits on the track.
It’s been well documented, by elite race/test driver Randy Pobst and others, that the GT4 suffers from a case of understeer from the factory (see here, here, or here). Pobst also mentions that, on track, the Cayman GT4 feels “slightly underdamped,” particularly over bumps. As long time friends, TPC Racing owner Mike Levitas has discussed these characteristics at length with Pobst, exchanging notes and feedback on the GT4’s handling on track. Using a combination of data gathered at the race track and notes provided by Pobst, Mike has spent the better half of the last year sorting out the balance of the GT4 for track use.
The TPC Racing Stage 2 GT4 Suspension includes a DSC Sport controller with a GT4-specific calibration table, rear toe links designed specifically for the GT4, and TPC Racing proprietary sway bar settings and alignment specs. Together, the components of the package work together to reduce understeer and improve damping for a better handling and perfectly balanced Cayman GT4.
Masking the understeer issue is pretty easy to do. In fact, Randy already shared his trackside quick fix in his second Motortrend review of the GT4:
I got so frustrated that I crawled under its gorgeous body and adjusted the anti-roll bars myself: full soft front, full hard rear, textbook to reduce understeer. It certainly helped, but the overriding feel remained a numbing push, hurting the response through the middle of the corners.
However, as his experience suggests, adjusting the sway bars doesn’t fully solve the issue with understeer the car has coming out of the factory. The other inexpensive – and vital – step in reducing the GT4’s understeer is a proper alignment, which Randy also addresses in the same article. It’s something the TPC Racing team does very, very well.
Identifying the Problem
However, Mike Levitas adjusted the sway bars and aligned the car. And aligned it again. And aligned it a few more times. However, regardless of what he did, he continued to walk a fine line between that numbing understeer and dangerous snap oversteer. So he looked at the data. Based on the data from multiple outings at Virginia International Raceway and Summit Point Motorsports Park, Mike determined that the rear toe curve was the culprit. One can set the static toe settings exactly where they should be, but as the suspension travels the toe curve produces some less than ideal characteristics.
Finding the Toe Curve
After multiple progressions of track days, street testing, and parts development, Mike developed an improved toe link specifically for the rear of the GT4 that reduces the toe deviation. The package, paired with the proprietary TPC Racing specs, allows for optimal toe settings, both statically and when subjected to suspension travel in high load applications. What this means is even at the highest of g loads the toe settings are still optimal for grip. In fact, it made such a vast improvement we were able to soften the rear dampers using the DSC Sport controller for even more grip on both corner entry and exit.
Paired with a DSC Sport controller to improve damping, the TPC Racing GT4 Toe Link Kit transforms the GT4 into what it always should have been from the factory: a perfectly-balanced mid-engined, normally-aspirated, manual transmission drivers’ car that is just at home on the track as it is on the street.
While TPC Racing already offers a toe link package for the 981 and 718 that fits the GT4, it is the proprietary offset bushing design that sets this package apart from any other GT4-compatible toe link package on the market. This is the only toe link package on the market designed to optimize the toe curve on the rear Macpherson strut design of the Porsche Cayman GT4.
In the words of Randy Pobst himself, “I marveled at the balance and control of the TPC-tuned Porsche GT4 I drove at Summit Point. TPC Racing makes this great car better to drive.”