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2005 Mazda RX-8 - Tire Review

Our test should give you a good idea of the characteristics of a wider, stickier tire.

Jun 20, 2010

Bridgestone Potenza Re-11
Size 265/35R18
Type Extreme performance summer tire
UTQG 180 A A

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Key Features
Molded 9/32-inch tread depth

Asymmetric tread pattern features massive outer shoulder blocks interlocked with a notched circumferential intermediate rib for lateral stiffness, enhanced steering response and dry cornering traction.

Inboard, a continuous intermediate rib and notched shoulder rib are separated by wide, straight circumferential grooves that provide water evacuation to resist hydroplaning and enhance wet traction.

Incorporates Bridgestone's 3-D Seamless Stealth technology originally introduced in its Formula 1 and GP2 racing tires.

Asymmetric internal structure helps distribute footprint pressure more evenly by keeping the straighter outboard sidewall from "falling down" while helping the more rounded inboard sidewall resist "falling away" during aggressive cornering.

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Test Mule
'05 Mazda RX-8
Test Driver
David Pratte, regular contributor to Modified
Test Track
Toronto Motorsports Park: 1.85-mile, 11-turn road course
Test Conditions
76 degrees Fahrenheit, dry and sunny

Consider this a sneak peek at our latest project car as well as a prelude to a more detailed analysis of Bridgestone's new extreme performance summer tire, the Potenza RE-11. Bridgestone's slogan for this tire is "for circuit and street," and since we've already tested these on the street using a Honda S2000 (Aug. '09), we've focused this test on the circuit.

As a point of comparison, we baselined our stock RX-8 (OK, it has a Mazdaspeed cold-air intake and strut tower brace) around Toronto Motorsports Park's 1.85-mile road course on the OEM 18x8-inch wheels and OE-sized 225/45ZR18 Toyo T1Rs. Keep in mind, this isn't a proper comparison because the T1Rs aren't in the same extreme performance class and they're not nearly as wide as the RE-11s. Our test, however, should give you a good idea of the characteristics of a wider, stickier tire like Bridgestone's RE-11.

After optimizing tire pressure using a tire pyrometer to measure temperatures across the contact patch, we recorded a fastest lap of 1:29.66 on the OEM wheels and OE-sized T1Rs. The relatively narrow contact patch provided by these tires resulted in fairly severe understeer, making it difficult to carry much speed through the corners. A lack of mid-corner grip was also a limiting factor, making it difficult to carry good speed onto the straights.

We then swapped on the 2-inch-wider Volks and 265/35R18 Bridgestone RE-11s and went through the same process to optimize tire pressures using a pyrometer. There was an immediate change in the RX-8's attitude, most of the understeer now having been replaced by crisp turn-in response and excellent mid-corner grip. This translated to much higher corner exit speed and resulted in higher top speeds down the straights. The RE-11s also provide a lot of useful feedback as you approach their limit of adhesion, making it easy to tell when too much speed has been carried into a corner. Breakaway is gradual and predictable, so recovering from a slide is quite easy.

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Having dialed in hot tire pressures of 39 psi front and 37 psi rear, we recorded a best lap of 1:25.82, an improvement of almost 4 seconds. Anyone who takes his car to the track regularly will understand that a 4-second improvement is absolutely huge. You'd literally have to double the output of your car's engine to achieve a similar improvement, and we all know doubling horsepower is a lot more expensive than investing in some high-quality extreme performance rubber like Bridgestone's amazing RE-11.

More details to follow on our RE-11 evaluation in the first of our RX-8 project car stories.



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