General Motors has made two different types of Michelin run-flat tire available for the C8 Corvette Stingray. The Michelin Pilot All Season 4 is fitted as standard on all three trim levels (1LT, 2LT and 3LT), while the Michelin Pilot Sport 4 S is offered as part of the Z51 Performance Package, which costs $5,995 and is fitted to over 60 percent of C8 Stingrays currently sold. Today, we’re looking at the differences between the two sets of rubber.
Incidentally, both of the tires available for the C8 Stingray contain a “4,” which could make identifying and referring to them somewhat confusing. Either way, the Pilot All Season 4 is intended to provide a compromise for all seasons. By contrast, the Pilot Sport 4 S is a summer-only tire suitable solely for dry weather (with reduced capability in wet conditions) and associated summer temperatures. The Pilot Sport 4 S will provide more grip, but it’s less optimal than the Pilot All Season 4 on days with rain, cold temperatures or even snow.
|Pilot Sport All Season 4||Pilot Sport 4 S|
|Availability||Standard on Corvette 1LT, 2LT, 3LT||Included with Z51 Performance Package|
|Type||Performance all-season wet & dry grip||Ultra high-performance summer|
|Warranty||45,000 miles||30,000 miles|
|Speed rating||(Y) – in excess of 186 mph||(Y) – in excess of 186 mph|
|245/35ZR19 89Y weight (pounds)||27.47||26.96|
|305/30ZR20 99Y weight (pounds)||35.21||34.90|
|UTQG Treadwear rating||540||300|
|UTQG Traction rating||AA||AA|
|UTQG Temperature rating||A||A|
The key figures in the table above are the Treadwear ratings quoted in the U.S. Department of Transportation National Highway Traffic Safety Administration’s Uniform Tire Quality Grade (UTQG) standards.
These are based on information provided by the tire manufacturers, who do not all use the same methodology to rate their tires. However, it is considered safe to compare Treadware ratings of tires from the same brand. In this case, the Treadware ratings of 540 for the Pilot Sport All Season 4 and 300 for the Pilot Sport 4 S are significant.
They imply that a softer compound is used for the Pilot Sport 4 S. All other things being equal, this implies that it will provide more grip than the Pilot Sport All Season 4 for as long as it lasts, but also that it will not last as long. Supporting evidence comes in the form of Michelin’s own warranty for both sets of tires, which lasts for 45,000 miles in the case of the Pilot Sport All Season 4, but only 30,000 miles for the Pilot Sport 4 S.
Another interesting detail (though of a more subtle kind) can be found elsewhere in the table. Each 245/35ZR19 Pilot Sport 4 S fitted to the front of the Chevy Corvette Stingray is 0.51 pounds lighter than its equivalent Pilot Sport All Season 4. At the rear, the 305/30ZR20 Pilot Sport 4 S has a weight advantage of 0.31 pounds per tire. The total weight saving around the car is therefore 1.64 pounds.
These are very small differences, but ones that become slightly more significant when we consider that it represents unsprung weight, which should be kept to a minimum in a high-performance vehicle like the Corvette. More importantly, it’s also vital to reduce the weight of any rotating object, especially when that object has as large a diameter and as great a rate of spin as a tire.
Inertia and momentum are different names for the same thing. We complain about the first when it prevents something from moving, and about the second when it prevents something from slowing down. In those terms, the lighter Michelin Pilot Sport 4 S tire has lower inertia, giving the C8 Corvette Stingray better acceleration, and less momentum, which helps with the braking. The differences are minor, but if we’re driving on a track and timing it to the nearest hundredth of a second we want all the help we can get.
Bottom line: for those who desire ultra-high-performance driving in summer conditions, the Pilot Sport 4 S is the optimal choice. But in cases where ultimate performance is secondary to all-season driving ability, the Pilot Sport All Season 4 is the way to go. The all-season rubber is also likely to deliver a long tread life to boot.