Luke@tirerack

Tires tested:
Dunlop Direzza Sport Z1 Star Spec (Extreme Performance Summer)
Dunlop Direzza ZII (Extreme Performance Summer)


Vehicles used:
2012 BMW F30 328i Sedan

In the Extreme Performance Summer tire category, the Dunlop Direzza Sport Z1 Star Spec has a strong following among driving enthusiasts, autocrossers and track-day drivers. And it's for good reason — this tire has a reputation for delivering impressive dry traction and well-balanced capability in all directions of the friction circle — cornering, acceleration and braking. All this packed in a tire that you really can drive to and from the track.

When rumblings of its replacement began to surface in the summer of 2012, fans of the Direzza Sport Z1 Star Spec debated the pros and cons of any change while they waited to see if Dunlop could find performance improvements without losing the good in an already great tire. Dunlop's development target was simple if not easy: improve dry traction and handling without sacrificing any of the wet or wear characteristics of the Direzza Sport Z1 Star Spec.

What Dunlop came up with is simply called the Direzza ZII. Short and straight to the point, the ZII looks the part of a dry track performer that begs to be driven hard, with a more solid tread pattern than the Z1 Star Spec. Dunlop is bringing the Direzza ZII to North America in early 2013, and when it arrives we'll do a comprehensive road and track test to find out how it compares with other tires in the category. In the meantime Dunlop brought us a set of production-spec tires to try out before we closed our test track for the season. We also pulled a set of Z1 Star Specs off the shelf to benchmark the ZII and get an idea of how well Dunlop hit their mark.

As the autumn afternoon temperatures hovered around 60° F we set cold tire pressures to our standard tire test setting of 35psi front/rear, and scuffed in both sets of tires to wear off any mold release. We then got started by running some baseline laps on the Direzza Sport Z1 Star Spec. True to the tire's performance in past tests, this tire goes about its business with minimal fanfare and rewards a smooth driving style.

In many instances the balance of the car with Direzza Sport Z1 Star Spec tires has just enough rotation at the rear to help the car glide around the corner, requiring minimal steering input to manage the few degrees of drift. Aggressive or early throttle input powering away from the corner can create a little power-on oversteer, however. Steering behavior is relatively good as the tire drives down to the apex, but you have to lead it just a little bit or risk falling behind when multiple steering inputs are required. Maneuvers such as the multiple side-to-side inputs of our five-cone slalom, as well as the right-left-right of our increasing radius S-turns, reveals the one potential weakness of the Z1 Star Spec, where the rear can get out of phase with the front, resulting in some transitional oversteer if not driven smoothly. Earlier and smaller steering inputs help tame it, as does keeping some weight on the rear tires. Avoid big speed adjustments mid-slalom or risk the tail wagging the dog.

With the Direzza Sport Z1 Star Spec tires still warm from their exercise, we hopped into another of our test cars shod with the Direzza ZII tires and set off to see what they have. From the first turn it was apparent this isn't the same tire. The Direzza ZII displayed noticeably more direct and positive steering response from the front tires. So much in fact, that we ran over a few apex cones in the first half of the first lap due to how the car was now diving to the apex with real authority. Lateral stability through the slalom was noticeably better, with a considerable improvement in composure at the rear of the car. Acceleration traction was noticeably better too, as this tire let us use much more of the torque of our turbo'd BMW 3 series test car, allowing for harder and earlier throttle application that results in forward progress, not sideways motion as might happen with the Z1 Star Spec. It's hard to say that the Direzza ZII has significantly more steady-state lateral grip than the Z1 Star Spec, but it does use what it has much more effectively. This pumps up driver confidence in rapid transitions and high speed maneuvers, resulting in higher velocity and lower lap times.

We then turned on the track's sprinkler system to make a quick assessment of wet performance. Once the track was thoroughly soaked we had time in the schedule for just a few laps on each tire. Here the Direzza ZII again showed a noticeable advantage over the Direzza Sport Z1 Star Spec. The steady-state overall grip level was similar, but the ZII was much more predictable at the limit, with noticeably better communication of where the limit is, along with faster recovery once any slide began. It was just plain easier to go faster with the Direzza ZII.

Test lap times dry/wet

Dunlop Direzza Sport Z1 Star Spec 29.56 / 35.00

Dunlop Direzza ZII 29.08 / 33.84

Time Difference -0.48 / -1.16

We didn't run enough laps to begin to see significant wear on either tire, but what there was already showed the Direzza ZII was wearing at least as well as the Z1 Star Spec.

So, let's see — faster and more predictable in the dry and wet, and at least equal wear rate. Sounds like Dunlop hit the mark with the Direzza ZII. We'll be doing a full road, dry and wet track comparison in 2013 to see how the Direzza ZII compares with other tires in the Extreme Performance Summer category. Stay tuned.


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Luke@tirerack

here's a link to our introductory drive report

http://www.tirerack.com/tires/tires....&affiliate=BD5