In a perfect world, every track rat would have a tow vehicle and trailer to cart themselves and their purpose-built road course builds to and from the race track. Unfortunately that’s just not feasible for the majority of gearheads for an array of reasons. But, as our Project M-Track3r E46 M3 illustrates, that doesn’t mean there isn’t serious capability to be had within the realm of daily driven machines.
To further complement that notion, we took the M3 out to a technical road course to test out a set of Falken Azenis RT615K tires at speed. These Falkens are DOT-legal and offer substantial grip for both street and track use, and particularly in climates like Southern California, if you’re sure footed enough you may even get away with running them year-round despite the summer tire specification.
But the real question is how these meats stack up against more common alternatives – are we going to see a noticeable benefit from the swap versus your typical road tire? Moreover, is the RT615K a suitable tire off the track and traversing the various imperfections of public roads – a situation that it’s likely to spend the majority of time? We made the trek out to Willow Springs, Streets of Willow (clockwise), about ninety miles north-east of downtown Los Angeles, to find out.
One of the reasons that Project M-Track3r makes a great platform to test the Falken Azenis RT615K on – aside from the inherently well-balanced chassis of E46 BMWs – is the fact that this car, much like the tire, has been tuned to serve double-duty as both a street-driven mode of transport and a legitimate on-track performer.
The BMW is what we would consider a mid-level budget build, designed for a road racer on an average budget. We picked up the car with a number of surprisingly well-chosen modifications already done to the car, including Eibach sway bars and a big Brembo GT brake kit that boasts four piston calipers up front that clamp down on 380mm discs. To stand up to the rigors of the high-performance abuse, the M3 had also been fitted with an uprated clutch and flywheel, as well as a Koyo radiator and the requisite cooling fan.
Along the way we added Bilstein Clubsport coilovers to get more control over the suspension tuning, a set of Whiteline polyurethane control arm bushings to help tighten things up at the rear end of the car, and some light-weight Forgeline wheels to reduce rotational mass. These modifications, along with Project M-Track3r’s ESS Tuning 475 hp supercharger kit, have the M3 well on its way to being a proper track weapon, but as any road course veteran will tell you, it all starts with the tires – hopefully the only part of your car that will ever make contact with the tarmac.
Along with the notable distinction of being the oldest permanent road course in the United States, Willow Springs offers a plethora of different options for those who like to go fast. Along with a karting track, quarter-mile paved oval, skidpad, and other racing facilities, the motorsports park offers two main road courses: Big Willow and Streets of Willow.
Big Willow is considered the facility’s main track – a fast 2.5 mile, nine-turn course with a configuration that has not changed since it was built in 1953. Over the years, Big Willow has played host to a multitude of professional and club racing events. With steep elevation changes, a long main straight, fast corners and a massive sweeper that requires a strong dose of courage to enter at the proper speed, Big Willow is iconic among road racers for good reason. However, if you’re looking to truly test the handling limits of a car, you’ll want to head up the hill to Streets of Willow.
While smaller than Big Willow at 1.6 miles and generally narrower, Streets of Willow is a much more technical course that offers little forgiveness for poorly setup cars and ham-fisted driving. Its 14 turns offer a wide range of different handling challenges. Its steeply banked hairpin – also known as The Bowl – is notorious for tossing vehicles off track if approached incorrectly with too little grip.
The course also features a chicane that’s entered blindly when the course is run in clockwise configuration, and Turn 1 in this same configuration can be taken flat out in most cars, provided the driver has the courage and experience to do so.
In short, you’d be hard pressed to find another road course in the region that offers such a comprehensive evaluation for a set of race-inspired tires like the Falken Azenis RT615K. Additionally, the E46 platform is just small enough to be able to make good use of the relatively narrow track.
The origins of the Falken Azenis RT615K can be traced back years ago to the introduction of the RT215, the model which initially served as Falken’s offering for enthusiasts that wanted to participate in autocross and track day events, while also driving the car to and from the track on the tires they competed with.
The RT215 was later replaced with the first version of the RT615. Later, with the expansion of rule set for Street Stock classes in SCCA, tire development escalated and more manufacturers got involved, in turn upping the ante for the industry as a whole.
The end result was more tire options for enthusiasts, which created an entire segment with numerous options for DOT-legal track/street tires including the BFG Rival, Bridgestone Potenza RE71R, and Dunlop Direzza among others.
As the successor to the RT615, the RT615K is said to offer even more responsive turn in, mid-corner stability, and the ability to get on throttle earlier on corner exit. “The RT615K now sports more dry grip and handling without giving up the predictability or the wear characteristics of the previous version,” says James Yim of Falken Tire. “This new compound improves grip, and extra care was also taken to handle the increased heat generation of track use.”
It was a very impressive tire for a street tire – it made a ton of grip and was easy to drive on – Conrad Grunewald
But don’t get this versatility confused with the role of an all season tire. “The RT615K is not created to handle low ambient temperature conditions for street use”, cautions Yim. “If the outside temperature is 45 degrees Fahrenheit or below, extra care should be taken until the tire reaches proper operating temperature range. Additionally, the tread design of the RT615K was created for dry performance with a bit of wet surface grip capability – heavy rain conditions should also be approached with caution.”
Commentary from Professional Driver Conrad Grunewald
Conrad started drag racing in 1995 while living in Houston, Texas. After five years of drag racing, Conrad wanted to try road racing so he attended a racing school at Laguna Seca in 2000. He then quickly decided that road racing was the route that he wanted to pursue. After racing his first full season in 2002, he turned to a new form of motorsport, drifting. Conrad’s first year of drifting was in the D1 series in 2004, where he was one of 12 drivers representing the USA in the USA vs. Japan shootout. In 2005 and 2006 he focused his attention on Formula DRIFT, as it was quickly becoming the premier drifting series in the US. In 2007 Conrad was given the opportunity to run a full Formula Drift season in a Nissan 240sx. .
The wait was well worth it as he finished 4th in the team’s first event in 2007. The 2008 season was a dream come true, being an American driver in an American car. In 2009 Conrad started CGR (Conrad Grunewald Racing), and began building a 2010 Camaro SS in conjunction with Luke Lonberger at Blu808 to compete in the 2010-2015 Formula Drift Championship.
“It was a very impressive tire for a street tire – it made a ton of grip and was easy to drive on,” explained Conrad Grunewald. “It’s common on a lot of street tires to break traction as soon as you get on the edge of grip, but that’s not the case with the RT615K, it was very well balanced. The cornering forces out of the tire was impressive for a street tire, even as it got hot, the Falken performed very well. Usually the performance of street tires begin to fall off once you get heat into them and that wasn’t the case. Actually, some of our best times were set when the tires were at its hottest.”
We inflated the tires to 26 pounds while cold in order to generate 32-33 pounds of pressure at operating temperatures, which we then verified after running five or so laps around The Streets of Willow. The benefits of the RT615K versus a conventional street tire are undeniable – the M3 posted a best run of 1:25.8, which is within two seconds of its 1:23.9 on 40 tread wear race semi-slicks, which would of course not be DOT legal, and therefore not usable on the street. “The Falken RT615K handled great – even better than we anticipated”, says Mark Gearhart, owner of Project Track3r. “The improvements over the previous model of this tire (the RT615) are immediately noticeable.”
The RT615K is perhaps best suited for autocross use – the tires heat up to operating temperature quickly, so there’s not a lot of prep work to get maximum grip from them. A careful racer could probably also use these for endurance racing, but when the tires start to overheat they do get slick, so thoughtful inputs would be recommended for prolonged competition use.
A typical 20-30 minute track day session or autocross seems to be the sweet spot for these Falkens. Once tire temperature exceeds normal operating threshold they do tend to get a little greasy, but most of the time that’s really a matter of adjusting your driving style rather than a fault of the tire compound.
But what really makes the RT615K a standout is how well it also works out on the street. Despite the stiff sidewalls, road noise is kept to a minimum.
From our experience with these Falkens, it wouldn’t be unreasonable to expect to get about 8,000 miles out of them on a daily driven car, including a couple of track days along the way – and all of it with the convenience of never having to swap wheels and tires regardless of whether you’re setting a lap time or headed to the grocery store.