Run-Flat Tires That Don't Flatten Performance
Consumers have long been lukewarm in their acceptance of run-flat tires. While many people like how a run-flat tire eliminates the hassle (and potential danger) of road-side tire changes, they've also found them to be more expensive, harder to replace, less supple in terms of ride quality and lacking in overall tire grip and performance as compared to an otherwise equivalent regular tire.
In the past 12 months, however, a couple of tire manufacturers have introduced next-generation run-flat tires. The companies say that these new tires deliver improvements in both ride quality and tire performance, thereby addressing at least a couple of people's concerns.
Last week we had the opportunity to test out these claims at a Michelin-sponsored event featuring Michelin's latest run-flat summer tire, the Pilot Sport PS2 ZP.
The regular Pilot Sport PS2 tire is well known for its performance and grip. They're fitted to our long-term 2009 BMW M3, a car our director of vehicle testing has described as having very "sticky rubber." Too that, the ZP ("Zero Pressure") simply adds run-flat functionality.
Of course, we doubt Michelin's tire engineers see it as "simple. " The company held its event at Spring Mountain Motorsports Ranch
, which is located about an hour's drive outside of Las Vegas. Spring Mountain has a number of different driving schools, including ones for the Lotus Elise and Mini Cooper. For Michelin's event, we were set up with the Ron Fellows Performance Driving School, which uses new Chevrolet Corvettes, including the Z06 and ZR1.
The Corvette is a good test vehicle for the Pilot Sport PS2 ZP because it comes from the factory with run-flat high-performance summer tires. Notably, the original fitment tire isn't a Michelin (it's a Goodyear tire), but Michelin fitted the Corvettes with varied tire set-ups and let us drive for two main comparisons.
Comparison Test One: Pilot Sport PS2 versus Pilot Sport PS2 ZP
This handling test was conducted on a small cone-based autocross course that had about half of its length watered down with a water truck. This provided the opportunity to feel out a base Corvette coupe's limits in both wet and dry conditions. On the dry part of the course, overall tire grip and response was very similar for the regular Pilot PS2 and the run-flat PS2 ZP. On the wet section, however, there was a noticeable difference, with the regular tire providing additional traction (i.e., the regular PS2-shod Corvette could be driven faster than the run-flat Corvette before each went out of control).
Michelin's representatives weren't surprised by our observations. They noted that the regular PS2 replacement tires that happen fit the Corvette were actually designed as original equipment tires for BMW (BMW M5 rear tire for the Corvette's rear tires, and an M3 rear tire for the front of the Corvette) and that BMW specifically wanted Michelin to emphasize wet-weather traction.
For the Pilot ZP, however, the sizes that fit the Corvette are specifically designed for the car, and Michelin decided to engineer out some wet-weather traction in exchange for a bit more dry-pavement traction. We weren't able to notice this claimed increase in dry traction during the test, but we did walk away impressed that the run-flat version of PS2 gave up nothing to the regular PS2 in dry-pavement grip and predictability.
Test Two: Pilot Sport PS2 ZP versus OE Corvette Goodyear Eagle F1 Supercar EMT
There were two opportunities to comparison here, first on the wet/dry autocross course and then on Spring Mountain's dedicated road course. In both cases, we drove the high-performance Corvette Z06, which has wider tires than the regular Corvette coupe.
On the autocross, we noticed that the PS2 ZP provided superior grip on both the wet and dry sections. Essentially, we could drive the Corvette faster on the Michelin run-flat tires than the Goodyears before reaching the car's adhesion limits. The Z06 also seemed more controllable with the Michelins. This impression was backed up on the road course, where the PS2 ZPs approached (or went over) their limits more predictably. From the driver seat, the Corvette felt like it communicated more through the steering wheel and was easier (and more enjoyable) to drive with the PS2 ZPs than the Goodyear Eagle F1 Supercar run-flats.
Unfortunately, the one thing missing among all of this testing was some rough pavement to really evaluate ride comfort. We did try to take notice on how the regular PS2s and the PS2 ZPs reacted to some rough strips on the pavement. There was a difference -- the regular tires seemed more compliant and comfortable -- but it wasn't substantial.
Conclusion
Overall, we came away from the event impressed with the Michelins' PS2 ZP run-flats. Though we'd prefer to conduct our own in-house tire comparisons to eliminate the chance of bias, the test did seem to indicate that the PS2 ZP could be a good replacement tire for Corvette owners.Over on Autoblog.com, you can find a write-up similar to this one that covers Bridgestone's introduction of its new RE050A run-flat tire.
And though there are still the run-flat drawbacks of price and availability to consider, we feel comfortable extrapolating out our observations to other vehicles. If you're a BMW owner, for instance, and are unhappy with the run-flat tires currently equipped on your car, changing to the Michelin Pilot Sport PS2 ZP could be a good choice as a high-performance summer tire.
- Posted by
- Brent Romans July 24, 2009, 6:05 AM
- Permalink
- Categories:
- Automotive Technology, BMW, Car Advice Articles, Chevrolet
Hi, Brent. I think the Corvette ZR1 comes with Michelin Pilot Sport PS2 tires.
http://www.edmunds.com/insideline/do/Drives/FullTests/articleId=134347
http://www.michelinman.com/action/tires/find-by-vehicle/?year=2009&make=Chevrolet&model=Corvette&option=ZR1
It looks like you had fun! :jealous:
Suby: Thanks, a wording oversight on my part. ZR1 defintely comes with the PS2 ZPs. -- Brent
With an average price of almost $200 a tire, they can keep run flats. Truthfully, you really don't get a flat that often anyway. (This is coming from someone who has a 2008 Miata that has no run flats on it and no spare tire).
Many of the BMW Z4 owners would change out their run flats for normal tires and find it rode better, handled better and they were cheaper.
For the extra money you save not getting run flats, you can buy AAA and have them tow you when you get a flat...