Bremsentest: Porsche 718 Cayman GT4

Expectations were high when Porsche launched the second Cayman GT4 a year and a half ago. And they were basically fulfilled. But the top model of the 718 gang had a hard time surpassing what the GT models actually specialize in. The heart jumped in the triangle in view of the ingredients: naturally aspirated engine, 8,000 revs, hardly any filter – as if painted! The performance as such, however, didn’t quite get off the ground. At least not to the usual extent. Around 70 kilos more than the predecessor, plus the long gear ratio, understeer was a constant problem on the racetrack, and then something happened that should never happen to a Porsche under any circumstances. Something that wasn’t meant to happen and hasn’t happened since the dawn of time: The Cayman GT4 lost a comparison test! Because of the braking values!

The top priority

At Porsche, the brakes are not only part of the high performance standards, but also form their basis. Reason enough for us to investigate the cause.

It is important to know that the brakes at Porsche are not only part of the high performance standards, but also form the basis of them. It’s the benchmark discipline and therefore, by default, “best in class”: in the Cayenne, the Panamera, and even more so in the GT models, which made the defeat doubly bitter. And for us, it was the reason to investigate the cause.

But let’s start at the beginning, with the trigger of the tin-foil. In the 11/2020 issue, the Cayman GT4 was pitted against two of its (few serious) rivals: the M2 CS and an Exige Sport 410. Like the Porsche, both were on semi-slicks, and both were relegated to the back seats in no time at all. The slightly beer-bellied BMW lacked agility, and the Lotus couldn’t get its power-to-weight ratio around the corner properly due to a lack of lock. The end result: 1.0 and 2.7 seconds respectively behind on the Hockenheim lap – easy game for the Cayman, the usual picture.

But while its rivals converted their tire grip into excellent braking values, the Porsche ended up with a comparatively meager 34.4 meters-and in third place in the end. Much to the discomfort of the GT bosses, as we heard.

Nevertheless, we’re not talking about brake problems in the general sense here, of course. No, we’re talking about a detail that arises purely from the difference between the level of aspiration and the level of performance. And which is made interesting by the fact that it is not an isolated case. As our test history shows, all (!) sport-tired 718 Cayman GT4s brake worse than all (!) standard 718s on civilian rubber! How can that be? What turns the grip advantage into the opposite? Can’t the ABS handle the Michelin Pilot Sport Cup 2 N1 properly?

Porsche 718 Cayman GT4, Bremsentest

According to Porsche, the cause sometimes lies in the tire itself. The GT4 is not running a hot lap tire, but an endurance athlete that needs temperature to develop its full potential.

According to Porsche, the cause sometimes lies in the tire itself: in its make, compound, and related alignment. The N1 configuration of the Cup 2, for example, was explicitly designed to meet the requirements of track-day drivers, who are supposed to make up a large proportion of the GT4’s clientele. Accordingly, the development goal was less about spontaneous grip and more about keeping the performance level high even during longer track stints.

Simply put: The GT4 is not running a hot lap tire, but an endurance athlete that needs temperature to develop its full potential. “The optimum working window opens at 80 degrees,” says Jan Frank, specialist for motorsport/driving dynamics at Porsche.

In addition, he says, the GT4 rubber is specified differently. “The tires on the front axle are identical to those on the 991 GT3, while the rear ones have already been optimized in rolling resistance coefficient with regard to the tougher legal requirements, which represents a conflict of objectives with performance.”

To make matters worse, our measurement procedure does not necessarily benefit the GT4’s tire configuration. Our braking tests (ten tests from 100 km/h) are carried out with tires that have been rolled warm but are by no means precooked – a circumstance that BMW and Lotus coped with better.

So the question now is to what extent the Porsche achieves its maxims when it is preconditioned according to the package insert, so to speak? And how does it behave on a comparatively conventional summer tire, which, as mentioned, seems to suit the 718 better and is now also available as an option for the GT models?

Porsche 718 Cayman GT4, Bremsentest

The result for the Cup 2: The cold braking values are mediocre, and when driven warm it “merely” confirms the findings from the fateful test. Only the heated blankets push the braking distances below the 33-meter mark.

First impression of the new Michelin Pilot Sport 4S N0: spongier! The cornering dynamics soften noticeably due to the smaller-part profile, the front axle guidance tears off earlier, and the handling seems less defined. In short: The standard tire may be an everyday alternative, but it is not particularly sporty. Especially since the braking distances remain manageable, i.e. within the usual range. Although the standard compound is faster in maximum form, it cannot produce fabulous values.

And the same again applies to the Cup 2: The cold braking values are moderate, when driven warm it “merely” confirms the findings from the fateful test. Only the heated blankets push the braking distances below the 33-meter mark. In retrospect, this would have been enough to take home the comparison test victory, but it still falls short of the Zuffenhausen sports car standards.

The reason? Lies partly in the conditions: December in Hockenheim, six degrees outside temperature – these are not the conditions for setting records. Period. However, there are cars that deliver their braking performance in summer and winter. One in particular: the 911, from whose parts pool the GT4 brake also comes! And that’s the crux of the matter. Or as Porsche puts it: the difficulty. The ceramic system is a one-to-one adaptation from the GT3, which sounds chic, moreover quote: “pays into the equal parts strategy” (i.e. the savings account, editor’s note), but-and this is the point-is not a blanket advantage.

The balancing act

The conditions in the 911 are different from those in the 718: rear engine here, mid-engine here. So the system is not made for the Cayman, it has to be adapted to it. Specifically, the rear-axle brake is actually too large in relation to the 911, so the braking force is higher than the somewhat lighter rear end can handle. Jan Frank explains that the volume flow in the system is correspondingly difficult to regulate, but that the imbalance can be leveled out with the help of an ABS adjustment (overregulation). According to our measurements, however, this is not completely successful!

So it remains the same: Even under optimal or, shall we say, optimized conditions, the GT4 is a good brakeman, but not the best – neither within Porsche nor in the class context. But there’s always room for improvement. After all, the evolution of the 718 is not yet complete. One stage is still missing, the last, the ultimate: the GT4 RS, where expectations are even higher.

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