Falken Azenis RT-660 Tire Test: Autocross and Track

The Tires

Goals and Tools

We set out to answer two questions: First, how much of an improvement is the new RT-660 over the RT-615K+? Second, how does it compare to one of the category benchmarks?

At the time of our test, production of the new tire was just starting to ramp up for a Q1 rollout, so available sizes were limited. One of those was the 225/45R17 that’s typically used by ND Miata drivers in SCCA’s C Street autocrossing. It’s also the required tire size for the Solo Spec Coupe class, which has mandated the RT-615K+ for the past two years.

The test mule was a 2019 Mazda Miata–an SCCA Time Trials Nats winner–and for this test we used OE-sized, 17×7-inch wheels. This pinched setup better replicates that found in C Street and Solo Spec Coupe competition. We then chose the Bridgestone Potenza RE-71R as a benchmark since it works well when pinched and served as the target for the new Falken.

Our drivers for the autocross portion were a pair of multi-time national Solo champs, David Whitener and Andy Hollis. Hollis also handled the track driving at Harris Hill Raceway, where he has thousands of laps. The grippy asphalt at the Mineral Wells airport hosted our autocross testing.

Skidpad Testing

First Impressions

As always, we used a skidpad to establish optimal tire pressures. After a couple of circles in each direction to get a little heat in the tires, laps were made at a variety of pressures. Notes were also taken as to the feel of the tire, since driver confidence can be a key factor in ultimate performance in competition. We sprayed the tires at one point in the progression to see if heat management affected times. We then zeroed-in on final pressures by using small pressure increments in the reverse direction.

First up was the RT-615K+. At higher pressures, it was very manageable with easy turn-in and progressive breakaway. As pressures were lowered, it became less precise, but grip increased and lap times improved. This trend continued until lap times finally stabilized in the 24–28 psi range. Spraying the tires had an immediate positive effect, but only for a single 10-second lap. Reversing direction indicated an optimal pressure of 28 psi hot.

Staying with the Falken brand, we bolted up the RT-660. This tire delivered a similar overall feel to its predecessor, but with way more grip. Likewise, lowering pressures increased slip angles as the car leaned more, producing more lateral g-loads and quicker times. Spraying this tire had no discernable effect, though, even as optimal pressures were once again confirmed at 28 psi. The big story was the solid three-tenths improvement in lap times on a 10-second lap.

Next was our benchmark, the Bridgestone RE-71R. In past tests, we’ve found this tire to be fairly pressure-agnostic, centering around 28 psi as optimal and delivering crisp response at small slip angles throughout. Given that, we only did three rounds of laps in one direction to get relative steady-state lap times to compare to the RT-660. That result? The newcomer from Falken was a touch quicker.

Skidpad Results

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Autocross Testing

Do We Have a New Contender?

Our permanent test course loop consists of a five-cone slalom opposite a three-gate offset sequence, along with a pair of steady-state sweepers at each end–one on-camber and the other off-camber. Laps are done in pairs to see how a tire performs in the typical 50–60-second autocross. Driver swaps occur after doing two sets of two laps, and then tires are changed. The baseline tire is run at each end of the test to measure changes in surface, weather and driver skill.

After putting down a string of 24.7-second baseline laps, David said the RT-615K+ felt “easy to drive but lacked mid-corner grip.” Andy’s times varied, with a best of 25.2.

Changing to the RT-660, Andy lauded the high level of grip and slalom response as he ran about a half-second quicker than the baselines. David also averaged a half-second improvement but noted vagueness at the limit: “These tires will reward getting to know them.”

With the benchmark Bridgestone RE-71R in place, Andy continued to find time. “Love these tires. Very intuitive. Incredible slalom response.” David matched his RT-660 times, noting a decrease in sweeper grip balanced by quicker transitional performance: “Very confidence-inspiring.”

Bracketing our test on the RT-615K+ again showed each driver averaging within a tenth of his earlier baseline times, giving confidence in our results.

Autocross Results

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Track Testing

Can the New Tire Survive the Heat?

Traits that make a tire quick around the cones don’t always translate to the track. Long, sustained turns can overheat a tire’s compound, as can heavy braking from high speeds. Further, quick transitional response is not very important at most tracks, while predictable breakaway is.

Test day dawned clear, cool and partly cloudy. We ran each tire for a series of seven laps to allow the driver to grow more comfortable, as it’s a challenge to extract maximum performance in a single lap from an unfamiliar tire. Our bracketing session at the end was cut short due to fuel starvation, though we easily confirmed the test’s veracity with the three laps we did complete.

Our baseline RT-615K+ showed why it’s so popular among grassroots enduro teams, as it was easy to drive, needed little warmup time, and delivered consistent lap times: high 1:28’s, with a single flyer at 1:28.3.

Heading out on the RE-71R felt like home. It easily drove down to the apex, was very intuitive to keep at the limit in long sweepers with minor throttle changes, and put down power really well. That resulted in more than a second improvement in lap times versus the baseline.

The RT-660’s lap times fell about halfway between the other two tires. Its prodigious grip gave up some in long turns and was difficult to modulate–especially on a bumpy surface. It was also a challenge to trail-brake, causing it to lose time on corner entries after long straights.

Track Results

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Bottom Line

Falken is Back

One thing is clear: Falken is back in the 200-treadwear game. The RT-660 is a player, at least for autocross use. It will most likely take some car setup changes and driver familiarization to extract all that it has to give, but it delivers enough to be considered alongside other category front-runners.

While not its primary strength, the new Falken is a solid performer on track. The soft compound does have to be managed well for best results, especially when ambient temps are high, but it’s sticky and predictable. Welcome back, Falken.