I updated posts 60 and 62 which have test results with the "guide to the ratings". Here is the text of the ultra high performance article.
Quote:
Ultra-high-performance tires
Big grippers
Last reviewed: January 2008
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Tire Testing
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In our test of summer and all-season ultra-high-performance tires, we identified a few excellent tires from Falken, Michelin, Nitto, and Pirelli and found big differences in performance among models in the group.
These tires, also called UHP, are designed to offer tenacious grip and superior handling. Once found only on high-end sports cars, they are now on a wider variety of cars, including sports sedans and more-affordable sports cars, such as the Mazdaspeed3 and Saturn Sky.
UHP tires are Z-rated, meaning that they're capable of sustained speeds of 150 mph or more, and they often come in wheel diameters of 17 inches and up. As a trade-off for grip and handling, these high-end tires might be hard-riding and quick-wearing. The summer tires are useless on snow or ice.
We tested 21 sets of summer UHP tires and 15 sets of all-season UHP tires. Prices for both types ranged from $80 to more than $200 apiece for the 225/40ZR18 size we tested. Most summer UHP tires handled the important challenges on wet and dry roads very well. The all-season UHP gave up a little performance in return for better capabilities in wintry conditions. We found wide variations among the different performance categories, such as handling, braking, and noise, so there's plenty of room for the consumer to choose a tire tailored to individual preferences.
Audi driving around cones
WATER RIDE To test wet handling of ultra-high-performance tires, we drenched our new 2.5-acre dynamics area, then had drivers run quickly through a coned course.
A NEW TEST FOR TIRES
This year we ran a new wet-pavement test geared toward UHP tires. We created a handling course through closely spaced highway cones and wetted the pavement so the surface was slick. Then different drivers took turns pushing our Audi A3 3.2 test vehicle to its limits through the course on each set of tires.
We combined those results with our standard wet-cornering test, in which we drive at ever-increasing speeds around a circle of wet pavement, noting a tire model's peak lateral grip.
We hired a contract laboratory in Texas to conduct tread-wear testing for us on the government's tread-wear course, which is a road circuit designed to mimic both city and highway driving. We measured tread loss up to 12,000 miles of use. That lets us compare relative tread life from one set of tires to another.
Historically, tread life has been a low priority for UHP tires, and many don't carry tread-wear warranties. Most UHP tires still wear more quickly than lower-speed-rated counterparts. We found that wear varied from model to model and is worthy of consideration when considering which of two similar models to buy.
Performance evaluations
Overall scores in our all-season UHP tire and summer UHP tire Ratings are a weighted average for summer and all-season UHP tires emphasizing safety-related characteristics such as braking, handling, and hydroplaning. For all-season tires, snow traction and braking on ice are also factors.
Noise, comfort, and rolling resistance account for less in the overall score. Rolling resistance ratings, which relate to fuel economy, span from fair to excellent. To see how much fuel savings can be expected, we ran a highway fuel-economy test on the all-season UHP tires rated best and worst for rolling resistance and measured a 1.1 mpg difference in fuel economy.
We subjectively rate tire noise on smooth and rough asphalt and concrete surfaces. This year, we found two tires to be particularly noisy, the Toyo Proxes 4 and BFGoodrich g-Force T/A KDW2. The KDW2 was so noisy, it's only suited for hard-core enthusiasts.
We rate tread life but do not provide projected mileage to wear-out since it will greatly vary by how, where, and what you drive. Still, after our 12,000-mile test, the summer and all-season UHP tires were about 40 percent worn out.
Our tread-wear test was already in progress when we purchased the Pirelli P-Zero, so a rating for tread life is not available for that model.
Summer UHP tires focus on dry and wet grip, but the all-season UHPtires compromise some of that for winter grip. Some all-season variants, such as the Falken Ziex ZE-912, lean toward three-season performance; several other tires, such as the Continental ContiExtremeContact and Michelin Pilot Sport A/S, offer more credible winter grip.
This report was originally published in November 2007, the information presented here is current.
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Man, they really beat up the Proxes 4's that I loved so much! |
