Tire Test Results

Have We Reached the Performance Peak in Extreme Performance Summer Tires?

July 22, 2016

Tires Tested

Bridgestone Potenza RE-71R (Extreme Performance Summer, 245/40R18 97W)
  • What We Liked: Great steering feel, massive grip, still the champion on the track.
  • What We'd Improve: Loud and stiff even among this competitive set.
  • Conclusion: The most extreme tire in this test.
Dunlop Direzza ZII Star Spec (Extreme Performance Summer, 245/40R18 93W)
  • What We Liked: Eager handling, feels at home on the track.
  • What We'd Improve: Could be quieter on the road, could have more grip on the track.
  • Conclusion: Still a winner after all this time.
Falken Azenis RT615K (Extreme Performance Summer, 245/40R18 97W)
  • What We Liked: Very easy to drive on the track. Relatively well-mannered on the road.
  • What We'd Improve: A small increase in steering precision and ultimate grip would be nice.
  • Conclusion: A remarkably approachable Extreme Performance Summer tire.
Nexen N FERA SUR4 (Extreme Performance Summer, 245/40R18 93Y)
  • What We Liked: Confident dry grip and reasonable ride comfort.
  • What We'd Improve: Feels somewhat uncoordinated through rapid transitions on the track. Loud tread pattern.
  • Conclusion: A good place to start, but needs a little more development before it can compete with the best.

Vehicles Used

2014 BMW F30 328i Sedan

To some, the only criteria by which Extreme Performance Summer tires are judged are their dry lap times. The fastest tire around the track is the winner, and that's where the story ends. If this is you, we can save you some time: the Bridgestone was fastest. For the competitive autocrosser, this point of view is completely logical. The sport is defined by short, aggressive runs, and the only thing that matters in the end is the lap time and how many cones are hit. But what about the low-buck endurance racer who may spend two hours behind the wheel at a time? Wouldn't this individual be best served with a tire that is easy to drive consistently, lap after lap? Or consider the casual enthusiast whose daily driven vehicle spends one or two evenings a month participating in an SCCA Track Night in America or similar open track event. This individual may need a tire that can stand up to track use, but brings with it the least sacrifice for daily life. Time will tell if the inevitable next round of Extreme Performance Summer tires will feature a breakthrough technology that allows one tire to excel in every aspect, but for the time being we seem to have reached a peak in absolute performance. If you want to go faster, you have to give up something, which brings us back to a familiar theme - what are your priorities, and what fits best with how, where and what you drive?

To evaluate the ultimate performance and daily livability of some of the newest and best Extreme Performance Summer tires, we gathered the reigning champion Bridgestone Potenza RE-71R, our old friend Dunlop Direzza ZII Star Spec, the new-to-us and recently updated Falken Azenis RT615K and the brand new Nexen N FERA SUR4 for a Real World Road Ride and Performance Track Drive. Our evaluation used 2014 BMW F30 328i sedans fitted with new, full tread depth 245/40R18 tires mounted on 18x8 wheels.

What We Learned on the Test Track

Our 1/3-mile per lap test track course includes 90-degree street corners, a five-cone slalom and simulated expressway ramps. Run in both dry and wet conditions, the test track allows our team to experience the traction, responsiveness, handling and drivability normally only encountered during abrupt emergency avoidance maneuvers or competition events.

While they are true street tires, Extreme Performance Summer tires are designed to excel in competition use. Whether your preferred form of motorsport involves wheel-to-wheel racing, autocross, time attack, HPDE events or open track days, an Extreme Performance Summer tire may fit your needs.

Out on the dry track, the Bridgestone Potenza RE-71R proved that it is still the king in outright performance. The tire combined phenomenal lateral grip, crisp and immediate steering response and right-now braking to deliver a balanced and focused package. As if to send a gentle reminder that not too long ago it was the tire to have for extreme performance, the Dunlop Direzza ZII Star Spec was just a small step behind the Bridgestone and brought with it a similar personality. The steering effort was a little lighter, but no less direct, and the overall feel was natural, like an extension of the driver's body. Ultimate grip was slightly below the Potenza RE-71R, but only just. After stepping out of the car equipped with the Falken Azenis RT615K, it was striking how friendly and easily drivable the tire was. The outright grip and steering precision were not quite up to the level of the Bridgestone and Dunlop, but compared to those tires, lapping the Falken almost felt like it took about as much effort as a Sunday drive. Where the leaders required focus and concentration to extract 100% and balance on that edge, the Falken seemed indifferent to whether it was driven at 95% or 105%, creating a broad performance plateau and forgiving small mistakes with easy recovery. With a little more development, the Nexen N FERA SUR4 could be a force to be reckoned with. It has huge grip levels, as demonstrated by its dry skidpad figures, and its overall lap times were within a breath of the Dunlop. It was held back by a slight hesitation between when steering input was added and when the tire responded. This led to some disconnect between the front and rear axles, and the vehicle never felt completely settled in the rapid transitions of our course.

As is often the case, the wet portion of our track drive created more separation between the group than we found in the dry. Leading the way once again was the Potenza RE-71R, which was a little edgy at the limit, but provided the driver a usable expanse of grip just below that point. The Direzza ZII Star Spec relied on its fast reflexes and friendly at-the-limit behavior to overcome its lower ultimate grip and post an average lap time only .04 second behind the Bridgestone. Taking a small, but noticeable step back, we come to the N FERA SUR4. Though far from inadequate, it didn't have the available traction to work with that we found in the Bridgestone, and it wasn't as friendly as the Dunlop or Falken, but it did post an average lap time that was firmly the third fastest of the group. The Azenis RT615K once again proved incredibly easy to drive and felt fast around the track, but the stopwatch disagreed, revealing average lap times that were over a second slower than the best in this test.

What We Learned on the Road

Our 6.0-mile loop of expressway, state highway and county roads provides a great variety of road conditions that include city and highway speeds, smooth and coarse concrete, as well as new and patched asphalt. This route allows our team to experience noise comfort, ride quality and everyday handling, just as you would during your drive to school or work.

We're realistic here at the Tire Rack. We know many people reading this report will immediately skip to the dry lap times, followed by the test result charts, the "What We Learned on the Track" section, and then maybe, just maybe, read the bits in between. However, there are those who may be considering making the leap to an Extreme Performance Summer tire or trying to decide if something from the category is right for them, and it is important those individuals know what to expect when living with such a singularly focused product on a daily basis. To oversimplify, they are all stiff and loud, both to varying degrees. More on that later, but first we should address the often-overlooked benefit of driving these tires on the road; the street handling and steering feel are some of the best you will find.

The Bridgestone Potenza RE-71R will reward any driver willing to tolerate its on-road noise and stiff ride with street handling that borders on sublime. From the first degree of steering input added to the wheel, the Bridgestone reacted with linear progression. With real weight to the steering and feedback that communicated exactly what was happening at the contact patch, the driver could dial in millimeter precision, and the tire gave exactly that. Dunlop's Direzza ZII Star Spec delivered a satisfying combination of traits all its own. With less weight and resistance than the Bridgestone, but matching that tire in responsiveness and linearity, the Dunlop's steering felt smooth and fluid, and the tire was incredibly eager to change directions when requested to do so. The Falken Azenis RT615K didn't provide much feel on center, and was not as immediately responsive as the other tires in this test, but the steering effort built just off center, and was weighty and naturally progressive from there. The Nexen N FERA SUR4 had a nice level of resistance and response, but effort increased in a slightly non-linear way, and its on-road handling score was slightly behind the rest of the pack.

Without belaboring the point, if you're looking for a refined and comfortable performance tire for your luxury sports car, Extreme Performance Summer tires aren't the best choice. The Bridgestone had the stiffest ride of the group, and flooded the cabin with a great variety of noise. Dunlop's entry was a small step more forgiving over bumps, and though the quantity and type of noise was similar to the Bridgestone, the volume was turned down a notch. The Falken earned our team's highest objective score in both noise comfort and ride comfort, and it proved to soften the blow from road imperfections a little better than the other tires. The noise it created was loud, but it blended together in a slightly more agreeable fashion than the rest. Nexen's N FERA SUR4 essentially tied the Falken in ride comfort, but had the lowest rating for noise in the test, owing to tread noise that sounded more like an off-road truck tire than something intended for a passenger car.

Fuel Consumption Results

Our Real World Road Ride features a relatively flat 6.0-mile loop of 65 mph expressway, 55 mph state highway and 40 mph county roads along with three stop signs every lap. Our team drove each tire approximately 500 miles over the course of several days. Since we wanted to compare fuel consumption results that typical drivers would experience, our drivers were instructed to maintain the flow of traffic by running at the posted speed limits and sustain the vehicle's speed using cruise control whenever possible. They did not use hypermiling techniques to influence vehicle fuel economy.

Tire Test MPG* Gallons/Year
@ 15,000 Miles
% vs. Most Efficient
Bridgestone Potenza RE-71R 28.5 526.3 --
Dunlop Direzza ZII Star Spec 27.9 537.6 -2.1%
Falken Azenis RT615K 27.8 539.6 -2.5%
Nexen N FER SUR4 28.3 530.0 -.7%
*Our evaluation used Race Technology DL1 data loggers to record true distance travelled.

None of the tires in this test were designed with low rolling resistance as a high priority, and the difference in observed vehicle fuel economy across the group was negligible. The .7 mile per gallon difference between our lowest and highest observed fuel economy would result in an annual difference of 13.3 gallons of premium gasoline. At the current cost of $3.00/gallon, it would amount to an annual difference of $39.90 for drivers driving 15,000 miles per year.

It's important to note our test's fuel consumption measurements follow consistent procedures designed to minimize variables that could influence the results, however they do not represent an exhaustive, long-range fuel consumption study. While our procedures require the test vehicles in each convoy to run under the same prevailing conditions, the week-to-week differences in ambient temperatures, barometric pressures and wind speeds that we experience over a season of testing can influence vehicle fuel consumption and prevent the absolute mpg values of this test from being compared directly against those of others.

Larger differences in consumption between tires may indicate a difference that might be experienced on the road, while smaller differences should be considered equivalent. As they say, your mileage may vary.

Summary

For a product category with such a narrow focus, our testing revealed a wide variety of personalities within the group. If the lowest possible lap time is your primary concern, the Bridgestone Potenza RE-71R is the fastest around our track in both the dry and the wet, but is the least street-friendly of the bunch. Dunlop's Direzza ZII Star Spec gave our team a reminder of how good it truly is, delivering objective performance figures just behind the Bridgestone, but with fewer apparent tradeoffs than expected given its capabilities. The Falken Azenis RT615K is the least extreme on the street and the friendliest on the track. It can't match the Bridgestone for fastest lap, but is so easy to drive that we question if it wouldn't be faster over several hours of lapping. Assuming you're willing to live with the noise, the Nexen N FERA SUR4 is a good place to start in Extreme Performance tires. It has very high levels of grip through the corners, provides reasonable ride comfort, and is potentially quite durable based on the wear observed throughout our test.

Product Details

Bridgestone Potenza RE-71R (Extreme Performance Summer): The Potenza RE-71R is an Extreme Performance Summer tire developed for serious sports car, sports coupe and performance sedan driving enthusiasts looking for Bridgestone's fastest DOT-legal street radial. Starting with a clean-sheet approach and a virtual slick tread, all of the design features were fine-tuned to maximize performance, traction, handling and control. Performance-tuned for dry and damp conditions, the Potenza RE-71R, like all Extreme Performance Summer tires, tires are not intended to be serviced, stored or driven in near- and below-freezing temperatures, through snow or on ice. Read more.

Dunlop Direzza ZII Star Spec (Extreme Performance Summer): The Direzza ZII Star Spec is Dunlop's Extreme Performance Summer tire developed for serious sports car, sports coupe and performance sedan enthusiasts looking for race tire-like traction on the street or for use in autocross, drifting and track events. As an evolution of the Direzza ZII and continuing to use the same tread design, the Direzza ZII Star Spec's tread compound helps provide faster lap times from the start by developing more traction in temperate temperatures along with consistent grip on subsequent laps when the tires are fully warmed up. While this means the Direzza ZII Star Spec's tread compound accommodates a wider operating temperature range, it is not intended to be serviced, stored nor driven in near- and below-freezing temperatures, through snow or on ice. Read more.

Falken Azenis RT615K (Extreme Performance Summer): The Azenis RT615K is Falken Tire's championship-winning Extreme Performance Summer tire developed for driving enthusiasts looking for street-legal, motorsports-type performance. By combining world-class construction with an advanced tread compound, the Azenis RT615K is designed to maintain grip in both street and track conditions. Performance-tuned for dry and damp conditions, the Azenis RT615K, like all Extreme Performance Summer tires, is not intended to be driven in near- and below-freezing temperatures, through snow or on ice. Read more.

Nexen N FERA SUR4 (Extreme Performance Summer): The N FERA SUR4 is Nexen's competition-proven Extreme Performance Summer tire developed for serious sports car, sports coupe and performance sedan driving enthusiasts looking for race tire-like traction on the street or for tires for drifting, autocross and track events. Tuned for maximum performance in warm dry and damp conditions, the N FERA SUR4 is not intended to be serviced, stored, nor driven in near- and below-freezing temperatures, through snow or on ice. Read more.

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