Aug. 8, 2003
Grand Touring tires are designed for drivers who want to blend handling, high speed, ride and noise comfort. Traditionally, the tires aimed at this category in the US market have featured All-Season tread designs and compounds which were able to provide some traction in light snow but didn't always offer the level of summertime handling drivers wanted. The parameters of ride comfort and responsive handling are often at different ends of the design spectrum, proving to be somewhat of a challenge for tire engineers to solve.
Several European and Asian vehicle manufacturers have begun to equip their sports coupes, sedans and sport activity vehicles with more specialized Grand Touring Summer tires. These Original Equipment fitments give vehicle owners the look and performance that complement the image of their vehicle, while still offering civilized ride and noise comfort for the daily commute. These "three-season" tires are intended for people who either live south of the snow belt, or choose to use dedicated Winter / snow tires when the white stuff flies. The group of Grand Touring Summer tires often has higher speed ratings than many of their all-season counterparts, giving a hint at their sporting nature.
To evaluate the blend of comfort and performance characteristics Grand Touring Summer tires promise to deliver, Tire Rack team conducted a Real World Road Ride and Performance Track Drive, comparing the Bridgestone Turanza ER30, Kumho Ecsta KH11 and Michelin Pilot Primacy. We used 2003 BMW 330Ci coupes, and installed BMW's "standard model" tire size with 205/55R16 tires mounted on 16"x7.5" wheels specially designed to clear the larger front brakes on some of the E46 chassis BMWs, like the 330Ci. Our evaluation used new, full tread depth tires.
To better evaluate the effect on ride comfort and vehicle handling that replacing Original Equipment tires can make, we also included in our testing a fourth, 2003 BMW 330Ci with the Original Equipment 205/50R17 Goodyear Eagle RS-A High Performance All-Season tires mounted on factory 17"x7.5" wheels.
The Goodyear Eagle RS-A is produced with several speed ratings and in a wide variety of sizes. Its design is heavily influenced by its use as an Original Equipment tire by BMW, Volkswagen, General Motors, Chrysler and others. The Eagle RS-A features a subtle asymmetric tread design, with larger tread elements in the outside shoulder intended to deliver more responsive handling, cornering, and steering. Smaller tread blocks on the inside shoulder combined with wide tread and lateral grooves are intended to enhance wet and snow traction.
Out on the road, the Eagle RS-A exhibited good road manners, providing levels of ride comfort and road noise that were appropriate for tires in the High Performance All-Season tire category, and only moderately below the three Grand Touring Summer tires in this evaluation.
On the track in the dry, the Eagle RS-A offered respectable handling and performance, but was not able to match the average overall lap times of the other three tires in this comparison. The inherent compromises of its all-season design may have contributed to the fourth-place finish in average lap times, but helped give a good comparison to what a change in tires can provide.
On the track in the wet, the Eagle RS-A and its all-season tread pattern and compound were likely contributors to lap times that were not on pace with any of the Grand Touring Summer tires in this test.
The Turanza ER30 is produced specifically as an Original Equipment tire, and can be found on a variety of vehicles from BMW, Mazda, and Lexus. The Turanza ER30 is fairly conventional in its appearance, with subtly larger outside shoulder blocks to aid dry road cornering, a continuous, notched center rib to block tread noise from escaping from the footprint and improve steering response, along with circumferential channels and lateral grooves in the intermediate rows of tread blocks to help channel water and prevent hydroplaning.
On the road portion of the test, the Turanza ER30 was found to offer reasonable ride quality, especially for a tire with a W-speed rating, doing a good job absorbing the harsh impacts from expansion joints in the expressway. Overall handling was rated highly by our team, while noise comfort was found to be the best of the three Grand Touring Summer tires in this evaluation.
On the track in the dry, the Turanza ER30 provided stable cornering and predictable handling, providing an average overall lap time virtually identical to the first place Michelin Pilot Primacy. Drivers felt confidence under hard braking, and steering response was crisp.
On the track in the wet, the Turanza ER30 was also able to provide predictable handling and steering response. Stability in the sweeping corners was good, but could not quite match the average overall lap time of the first-place Pilot Primacy.
The Ecsta KH11, Kumho's Grand Touring Summer tire, does not have any Original Equipment fitments. It was designed as a replacement tire option for the drivers of sports coupes and sporty sedans.
The Ecsta KH11 features a silica-enhanced tread compound molded into an asymmetric tread design. Large outer tread blocks and a continuous center rib help provide stable cornering, responsive steering and high speed stability. Three wide circumferential tread grooves and multiple lateral tread grooves evacuate water from under the tire's footprint to resist hydroplaning and enhance wet traction. Internally, the Ecsta KH11 features twin steel belts reinforced by spiral-wrapped nylon cord to stabilize the tread area, enhancing treadwear, handling and high-speed capability while maximizing ride uniformity.
The Ecsta KH11 displayed good road manners, with our team finding the ride comfort and noise levels appropriate for a sporty Grand Touring tire. The overall handling around tight corners and fast highway on-ramps was not as crisp as the other two Grand Touring Summer tires in this evaluation, however.
On the test track in the dry, steering response was somewhat slower than the other Grand Touring Summer tires tested, but overall handling was predicable, making the Ecsta KH11 easy to drive at the limit. Feeling faster than it actually was, average overall lap time for this tire was only 0.29 seconds behind the first-place Pilot Primacy.
During the wet track testing however, the Kumho Ecsta KH11 could not keep pace with the Pilot Primacy or Turanza ER30. The Ecsta KH11 could not generate the level of cornering grip (average lateral g's) or quick overall lap time of the other Grand Touring Summer tires tested. The KH11 was still able to lap the wet track nearly 0.7 seconds faster than the 330Ci's Original Equipment All-Season tire included in this evaluation.
Used as an Original Equipment fitment on Audi, BMW, Mercedes-Benz and Saab, the Pilot Primacy molds a silica-based tread compound into an asymmetric tread design that features stable independent outer shoulder tread blocks (to blend dry road handling with wet cornering traction), a continuous center rib (which reduces noise while providing constant road contact to enhance straight line stability), and a high angle, grooved inner tread design (to further enhance wet grip and resist hydroplaning). Internally, the Pilot Primacy features twin, high tensile steel belts that are supported by Michelin's Banded At Zero (BAZ) technology (spiral-wrapped reinforcement) to stabilize the tread area to enhance handling and high-speed capability.
Out on the road, the Pilot Primacy was found to have fairly crisp, responsive handling, but came at the trade off of a moderately firm ride. Tread noise on the new tires in our evaluation was reasonable, but not rated as quiet by our team.
On the test track in the dry, the Pilot Primacy exhibited gentle understeer when driven at the limit, feeling not quite as precise as the Turanza ER30. This did not hold back overall lap performance, however, with the Pilot Primacy generating the highest lateral g's, and fastest overall average lap times of the tires tested.
Wet track performance was also strong, with the Pilot Primacy posting the fastest slalom, cornering g's and average overall lap times of the test.
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