May 23, 2022
Run flat tires provide security and peace of mind by allowing continued mobility for up to 50 miles at up to 50 miles per hour, even after experiencing a puncture that results in a complete loss of air pressure. The technology traces its origins back to the 1930s, but it took until the late 1980s before run flats were used as original equipment (OE) on a mass-produced vehicle. That vehicle was the legendary Porsche 959 supercar, and the original equipment tires were the Bridgestone Potenza RE71 Denloc, sealing Bridgestone’s place in history as the first OE manufacturer of run flat tires.
In order to provide the run-flat capability, early run flat tires featured heavy, unyielding constructions that helped earn a reputation for being stiff-riding and fast-wearing. Yet Bridgestone never stopped developing the technology, continually refining their products over the years to help reduce the tradeoffs associated with extended mobility. Each new generation has seen Bridgestone’s run flat tires move closer to the ultimate goal: a run flat with no compromises; one that is indistinguishable from a conventional Grand Touring All-Season tire; a premium touring tire, Plus.
Enter the DriveGuard Plus. Bridgestone’s latest generation run flat tire is designed to compete head-to-head with the finest touring tires on the market with no caveats or excuses. The manufacturer claims ride and noise comfort on-par with the best in the category in addition to the wet, dry, and wintertime traction one would expect from a premium Grand Touring All-Season tire. Plus, a 65,000 mile treadlife warranty.
We were excited to put Bridgestone’s newest run flat technology to the test. We knew that in order to be a success, the DriveGuard Plus had to be a serious competitor for non-run flat tires, so we weren’t going to take it easy. For the benchmark products, we picked two of the most comfortable touring tires on the market - the Goodyear Assurance ComfortDrive and the Pirelli P7 AS Plus 3. Our evaluation used 2022 Subaru BRZ Limited test vehicles fitted with new, full tread depth 225/45R17 tires mounted on 17x8.0 wheels.
Our 6.0-mile loop of expressway, state highway and county roads provides a great variety of road conditions that include city and highway speeds, smooth and coarse concrete, as well as new and patched asphalt. This route allows our team to experience noise comfort, ride quality and everyday handling, just as you would during your drive to school or work.
The P7 AS Plus 3 earned the highest score from our test drivers in the road ride portion of our evaluation. Its ride quality was the right blend of comfort and composure that allowed it to cushion impacts of all sizes and keep complete control over the vehicle’s vertical motion. Noise comfort was also top-notch, with nothing but a low-volume, broad blend of subtle tones over smooth surfaces. Even on the coarsest roads on our test route, the sound generated by the Pirelli’s tread pattern was never obtrusive or distinct. The Assurance ComfortDrive was also impressively refined on the road, and it tied the Pirelli in our metrics for ride quality and noise comfort. The Goodyear’s ride was slightly "softer" than that of the Pirelli. It absorbed larger impacts better, but also wasn’t quite as composed over some sections of our route. Noise was nearly indistinguishable between the two, with just a small amount of pattern growl from the Goodyear that was different, but no louder than the Pirelli. Ride quality from the DriveGuard Plus was nearly on par with the two conventional tires. It mitigated small impacts and undulations just as well as either competitor. It was only over larger bumps where the run flat construction made itself known. When encountering big impacts, the DriveGuard Plus seemed to reach its limit of travel slightly sooner than the other two tires, resulting in a slightly more noticeable disturbance for the vehicle’s occupants that likely would only be noticed when comparing tires back-to-back. Noise comfort was just a small step behind the leaders due to some faint, high-pitched cavity noise and a mild growl from the tread. It also is unlikely to be noticed if the tire was driven in isolation, but it stood out somewhat in this test.
Where the P7 AS Plus 3 separated itself from the competition was in the steering and on-road handling portion of our evaluation. The light, responsive steering was precise throughout the range of input, and the way it built effort felt natural and just-right for a touring tire. Steering from the DriveGuard Plus had more weight to it, requiring some additional force to elicit a response. While it was linear, our team expressed a desire for more mid-corner effort and stronger self-aligning torque. The Assurance ComfortDrive’s steering had some noticeable non-linearity to it, with a relatively large dead spot on-center that then ramped up quickly in response once loaded. At that point, it was alert and responsive and generally satisfying, but the lack of on-center feel hurt its score a small amount.
Our 1/3-mile per lap test track course includes 90-degree street corners, a five-cone slalom and simulated expressway ramps. Run in both dry and wet conditions, the test track allows our team to experience the traction, responsiveness, handling and drivability normally only encountered during abrupt emergency avoidance maneuvers or competition events.
Wet traction is arguably as high a priority for Grand Touring All-Season tires as ride and noise comfort. Most drivers in the U.S. will encounter wet roads at some point during their tires’ lifecycle, and the security provided by adequate wet traction is of the utmost importance. The Assurance ComfortDrive was the clear victor in our wet testing, sweeping the objective tests and all subjective metrics. Our test drivers noted that in the Assurance ComfortDrive they felt like they could actually drive the vehicle, as opposed to just managing the available traction. The steering was very responsive and pointed the front end with authority. Fortunately, the traction was sufficient to keep up with the demand, so it was useful and felt athletic, even in wet conditions. The DriveGuard Plus required a relatively minor 6 feet longer to come to a stop from 50 mph compared to the test-leading Goodyear. Its lateral traction was .03g lower than the leader, which is noticeable, and the average lap was a significant 1.14 seconds slower. The sizable gap in lap times was primarily attributable to the DriveGuard Plus’s strong desire to hang the tail out under power. The breakaway was gentle and controllable, but it was frustrating to contend with the wasted motion when using anything other than the strictest throttle discipline. The P7 AS Plus 3 was a sizable step back from the Bridgestone, and the gap to the first-place Goodyear was pronounced. Our drivers appreciated the tire’s communicative nature and that its attributes were in relative balance, but the available grip wasn’t enough to work with for anything resembling a quick lap. Trying to push for lap times resulted in stubborn understeer at corner entry and quick bursts of oversteer when trying to power away from the turn. Ultimately, the tire required our team to slow down and drive within the relatively narrow window of capability.
Dry track testing reversed the subjective ranking for the group, with the Pirelli coming out on top. While its lap times were mid-pack, the P7 AS Plus 3 genuinely impressed our drivers with its athletic and capable demeanor. Some additional traction would have helped to improve the lap times, but it delivered all that could be expected from a Grand Touring All-Season tire. The handling was balanced and neutral, fully utilizing all four tires with some mild rotation to help point the front and power away from turns. The DriveGuard Plus and Assurance ComfortDrive were essentially tied subjectively, with just .03 point separating the two. The DriveGuard Plus had a solid, weighty feel to the steering that was satisfying on the track, and it could easily rotate at the rear to help keep understeer at bay. The steering of the Assurance ComfortDrive was very responsive, lending an eager feeling to the front end that sometimes could cause the vehicle to dive down to the apex a little too quickly. Though it set the fastest average lap, that additional speed could also result in some mid-corner understeer, and our drivers noted it didn’t feel quite as crisp as the Pirelli, or even the Bridgestone in some situations.
Our light snow testing revealed that none of the tires in this group are standout performers, however, the P7 AS Plus 3 was the best in the test. While the traction it provided wasn’t incredibly high, it felt the most usable. It was the only tire our testers felt like they could actually drive, instead of just managing the relative lack of grip. Within its limits, it was balanced and controllable, and it led all subjective and objective metrics. The DriveGuard Plus was close to the Pirelli in pure longitudinal objective measurements. Looking solely at the acceleration and braking figures, it would appear the two were closely matched, but there was a noticeable difference in the subjective impressions. Our team wanted an increase in lateral traction from the front axle to help with directional changes around the handling track. Fortunately, the rear of the vehicle was comparatively well-planted, and even when it did break away, it was gradual and easy to catch. Rounding out the group was the Assurance ComfortDrive. Our team had positive comments about the steering feel, but unfortunately the traction provided couldn’t make the most of it. Ultimately, our drivers resorted to making small inputs and initiating turns as far in advance as possible to follow the shortest path around the handling track.
The P7 AS Plus 3 led the group on the ice, as well. Its 60’ acceleration time of 6.04 seconds was .42 sec and .82 sec ahead of the Bridgestone and Goodyear, respectively. It brought our test vehicle to a stop from 12 mph in 53.6 feet, representing an advantage of 8-10 feet over the competition. The DriveGuard Plus was squarely in the middle of the pack in acceleration, while it and the Assurance ComfortDrive were separated by a mere 2 feet in 12-0 mph braking, posting stopping distances of 61.5 feet and 63.8 feet.
In this test, we brought together three top-notch touring tires. Whether run flat or conventional construction, each one is sure to satisfy drivers on the road. The Pirelli P7 AS Plus 3 blends impressive ride and noise comfort with an athletic demeanor on the road and on the dry track. It leads this group of relatively modest performers in the snow but falls a step behind in wet traction. The Goodyear Assurance ComfortDrive seems the most comfort-focused of the group, with a cushioned ride and minimal tread noise. Additionally, it’s the objective and subjective performance leader in the wet. Unfortunately, it’s at the back of the pack in light snow traction. Bridgestone’s DriveGuard Plus is the only tire in the test that offers extended mobility, and it’s nearly a match for the premium, non-run-flat competitors in on-road refinement. The wet traction could use a small improvement to keep pace with the best, but it’s likely adequate for everyday driving. We would also like to see a significant boost in grip in snowy conditions.
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