NEWS: Test Driving Corvettes with Michelin's New Pilot Sport Cup Tires

July 30, 2009
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A funny thing happened on the way to the checkered flag at the 2003 24 Hours of LeMans: A Corvette C5R didn't win. Given the fact that the all-American heart throb already had two GTS class victories in a row under its belt (2001, 2002), and it was celebrating its 50th birthday, that loss was a tragedy.
The inevitable post-mortem revealed exactly why the two team Corvettes were beaten by the Veloqx Prodrive Ferrari 550 Maranello which finished tenth overall: tires. While the Ferrari was able to safely depend on their Michelins for two full driving stints, the Corvette team had to swap rubber every time it came in for fuel. Since service at LeMans is a sequential affair--with no work on the car allowed until refueling has been completed--the 15 extra seconds per stop needed to replace the Corvettes' Goodyear tires multiplied times 24 Hours consisted of ten full laps. That gap is what doomed the Corvettes to second- and third-in-class finishes behind the winning Ferrari.
This is where the classic Join Them To Beat Them strategy kicks in. As soon as Michelin replaced Goodyear as the Corvette Team's rubber of choice, winning at the Sarthe resumed. Let the record show that Corvette and Michelin conquered all foes in their class for four out of the past six years, including three victories in a row from 2004-2006. Add to that five American LeMans Series Driver, Manufacturer, and Team championships earned since 2004. This pair has won 51 out of the 59 races campaigned together. Need we say that rubber matters?
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It's also obvious that winning is an excellent way to strengthen the bonds between car and tire manufacturers. But trophies pale in comparison to knowledge accumulated which is why Michelin's mantra is "We race to learn before we win."
Michelin began cooperating with Corvette production engineers in 2001 when a Pilot Sport A/S (all-season) fitment with ZP (run-flat) capability was introduced for C5 (fifth-generation) Corvettes. Shortly after the 2003 LeMans debacle, when Michelin and Corvette joined forces for racing, that relationship intensified. Last year, Michelin Pilot Sport ZP radials were selected as the original equipment fitment for the spectacular ZR-1. Also, three new replacement applications were introduced: Pilot Sport PS2 ZP tires for C5 and C6 Corvettes plus new A/S Plus ZP rubber for use on C5s driven in inclement weather.
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Behind the scenes, Michelin has continued developing additional replacement tires for Corvette owners. The first A/S Plus tires with ZP capability were launched this year for C6 applications. And in the teeth of a July heat wave I ventured to Spring Mountain Motorsports Ranch near Pahrump, Nevada, to try out the latest Pilot Sport PS2 ZP radials just introduced for Corvette Z06s.
The Pilot Sport PS2 is the best performance tire Michelin offers short of the street-legal/track-tuned Pilot Sport Cup rubber. With scores of OE and replacement fitments already existing, PS2s are a favorite of manufacturers and owners alike. The list of other brands served includes Acura, Audi, BMW, Cadillac, Dodge, Ferrari, Ford, Infiniti, Lexus, Maserati, Maybach, McLaren, Mercedes-Benz, Mini, Nissan, and Porsche. This year Michelin is adding 43 new SKUS (stock keeping units) to further extend PS2 joy.
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Rather than employing a few-sizes-fit-many strategy, Michelin engineers tune and homologate each particular SKU for its specific car application. That's why there are 130 SKUs and 82 different sizes to accommodate 80 some car models. In addition, tuners such as Callaway, Hennessey, Pratt and Miller, and Specter Werkes turn to Michelin for assistance homologating PS2s for their higher-stress applications.
The 193-acre Spring Mountain Motorsports Ranch (SMMR), where I had the opportunity to evaluate PS2s in trying circumstances on regular C6, Z06, and ZR-1 Corvettes, is where only the most deserving car enthusiasts go after a life well spent. (Others can buy their way in; Memberships start at $15,000.) In addition to two major road courses - 1.5-miles, ten turns and 3.5-miles, 20 turns - SMMR also offers:
  • The Ron Fellows Performance Driving School
  • Lotus, Mini Cooper, and Radical driving schools
  • Membership in Club Spring Mountain
  • 8000-sq ft clubhouse
  • Swimming pool
  • Indoor firing range
  • Massage service
  • Garage rental
  • Go-kart driving school
  • Flight training
  • Racquetball court
  • Driving simulators
  • Meeting and training facilities
  • A Spring Mountain race series
  • Switchcars.com exotic automobile dealership
  • RV parking pads
  • Dyno Jet power assessment shop
  • PowerTec engine building shop
Condominium sales are already underway at SMMR with occupancy scheduled for later this year. Construction of an onsite Microtel hotel is also planned. The usual Nevada sin activities--gambling, bar hopping, and bordellos--are available a short distance off the SMRR property. One other attraction worth noting is a number of straight, level, lightly traveled, and rarely patrolled roads near Pahrump where 200+mph is possible on a good day with the right car. I speak from experience.
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Before Michelin allowed us to shred rubber on the track, the combined intelligence of the assembled journalists was doubled during a few short classroom sessions. The highpoints of what I learned are:
  • The PS2 has two distinct tread patterns and two different tread compounds aimed at optimizing both wet and dry adhesion.
  • A more flexible outer sidewall construction allows a controlled amount of flex during cornering so that the rubber patch in contact with the pavement grows under load to deliver maximum grip.
  • During straight-line driving, the contact patch is symmetrical for best acceleration and braking traction.
  • Both sidewalls and the overall PS2 construction are aimed at safely supporting the vehicle for 50 or so miles after a complete deflation.
  • The key to maximum dry grip is an outer groove-to-rubber ratio of 30-percent (tread block area more than twice the void area). The PS2's key to maximum wet grip is an inner groove-to-rubber ratio of 40-percent (ample area for water to be evacuated away from the tread).
Upon graduation, we were ushered to the 1.5-mile road course and a half-wet gymkhana to put our knowledge to work.
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Comparing a regular PS2 to the new ZP version of the tire on a regular C6 Corvette, I observed that the ZP has a distinctly stiffer feeling with less resilience. Fortunately, that doesn't seem to impose any notable deterioration in ride quality. The two were about equal in grip though the ZP version seemed to provide better control at the ragged extremes when keeping the tail in line can be a concern. In wet tests, I preferred the more controllable, predictable, and catchable standard PS2 (without ZP capability).
The second opportunity was to compare the new PS2 ZP to the current OE Goodyear Eagle F1 Supercar tires on Corvette Z06s. Here the amazing discovery was how much additional grip is provided by the new Michelins, now available as a replacement fitment. I can't think of a quicker or easier way to significantly upgrade performance than swapping out a set of used F1s for new Pilot Sport PS2 ZPs on any Corvette Z06.
On wet pavement, the PS2s bit through the water to hold the Corvette tenaciously to its cornering line. There was so much adhesion available that the front of the car chattered at the understeer limit as it held then lost grip in a highly predictable manner. The Goodyear was easy to slide around the course but its speed through the wet portion of the gymkhana was notably slower.
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Lessons done and points made, Michelin flagged off the best event of the day: hot lapping Corvette Z06s wearing Michelin Pilot Sport Cup tires, the race rubber that's also approved by our Department of Transportation for street use.
From my notebook: There's nothing this tire refuses to do. It generates tremendous stick and communicates far more clearly than most life mates. Turn-in is crisp and predictable. Braking adhesion lets you add yards to every straightaway. Ten laps on these tires is a calorie-consuming workout because of the significantly higher g-loads, speeds, and control efforts that accompany full use of true racing rubber.
For anyone with any car that's driven only on rare occasions, such as track days or banzai runs down dry back roads, your lucky prayers are answered if Michelin offers Pilot Sport Cup tires appropriate for your pet.
For dessert, I rode a couple of laps with racing great Ron Fellows at the wheel of a ZR-1. I was impressed by his quick and perceptive control inputs. Through any piece of track approximating a straight line, he was dazzingly fast. In transitions and sweepers, he demonstrated the uncanny ability to exploit every micron of traction and then some. His retirement from active participation in motorsports (possibly subject to review) is Team Corvette's loss but a major gain for those who enroll in his driving school.
Furthermore, Fellows is a gentleman with a genuine interest in discussing matters large and small with curious journalists and anxious-to-learn students.
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