Austin, Texas — Run-flat tires have always had two sides to them. On one hand, they allow you to drive to a safe or convenient place even when they’ve completely lost their air, and they free up the trunk space normally occupied by a spare.
However, run-flats can also produce a very harsh ride, and you can only get them for certain cars that originally came with them anyway—until now, that is.
Bridgestone has introduced a new line of tires, called DriveGuard, that it says is an industry first: replacement run-flat tires for mainstream vehicles that didn’t originally come with run-flats. They provide the convenience of driving on a flat tire in an emergency, but without the harsh ride when they’re full of air.
(Disclosure: Transportation, accommodation, and meals were provided to the author by the tire company.)
They’ll initially be available in 34 sizes, ranging from 15- to 19-inch, that should cover about two-thirds of the current range of cars, coupes, and wagons. The most popular fitments will include the Toyota Camry, Prius and Corolla; Honda Accord and Civic; Chevrolet Malibu and Cruze; Volkswagen Jetta; Ford Fusion; Nissan Altima; and Volkswagen Jetta.
Up close you can see the special cooling fins moulded into the tire to dissipate heat, which helps especially when run with pressure loss.
No more stiff sidewall suffering
Run-flats have a firm ride primarily because of their sidewalls. They’re much thicker than the sidewalls on a regular tire, since they have to be able to hold up the weight of the vehicle if they lose air. (In any tire, it’s not the tire itself, but the air inside it, that holds up your car.) They’re also lower-profile, which increases their strength, but also toughens up the ride.
DriveGuard tires use a new rubber insert technology in the sidewall, which allows engineers to make a sidewall that’s thinner and with a taller profile than on a conventional run-flat. It’s strong enough to hold up a vehicle, but provides a ride that’s comparable to a premium touring tire. While the exact distance you can travel depends on your speed and road conditions, Bridgestone says the tires can go for 80 kilometres at 80 km/h even when completely flat.
Pricing hasn’t been announced, but expect them to be about the same price as a premium touring tire. They won’t be cheap, but they’re not expected to be as expensive as conventional run-flats. Depending on the tire, there is a limited tread wear warranty of 80,000 or 100,000 kilometres, and a one-year/20,000-km no-charge replacement warranty.
The tire also doesn’t need a special rim, and can be mounted using ordinary tire equipment. If a shop can mount a performance tire, it can mount a DriveGuard, the company says. They can be repaired, but it will depend on how much abuse they took while being driven flat. A shop will have to dismount the tire and inspect the interior for liner wrinkling or rubber crumbs (pictured above), which will determine if it can be fixed or not.
Weather worries and restrictions
While you don’t need a special rim, your vehicle will have to be equipped with a tire pressure monitoring system (TPMS). Such systems are mandatory on all new vehicles sold in the U.S., but while they’re common on Canadian cars, they’re not required. Since run-flat tires don’t necessarily look any different when they’re low on air, there has to be an electronic warning.
The tires are all-season, and since their tread is asymmetrical, they can be rotated. There are no current plans to produce a winter version. SUV and crossover owners will have to wait, too: the insert technology hasn’t yet been adapted to the taller tires that these vehicles use.
Bridgestone is marketing the tires as a convenience item, and is specifically targeting women, by pointing out that they will still be able to get to work or get their children to school if they puncture a tire, or they won’t have to change a tire or wait for someone to come and help.
Handling like a touring tire
Although flat tires are far less of a problem than they have been in the past, mostly due to improvements in tire construction overall, a survey commissioned by Bridgestone found that a majority of drivers polled didn’t want the aggravation of a flat tire, and more importantly, feared losing control of a vehicle if a tire suddenly went flat.
Bridgestone set up several exercises at the Circuit of the Americas track, including one where I drove a DriveGuard-equipped Camry with a flat left front tire. It did pull slightly to one side, and the tire rumbled on turns, but that was as bad as it got. Even at 80 km/h on a straightaway, I was always in control of it.
That’s normal for a run-flat tire, but when I drove a set of DriveGuard tires against Bridgestone’s Turanza Serenity Plus, the company’s premium touring tire, it was tough to tell the difference, which is the whole point. The run-flat tires have a lot of lateral stability in tight turns, and they grip well on wet pavement, but the ride is pliable.
Their cost will put them on the radar of those who consider more than just price when shopping for tires—and these are usually the type of drivers who buy quality tires and maintain them, and are probably less likely to experience tire failure. They’ll be buying them as insurance, looking at the convenience and at not being stranded, just as Bridgestone’s advertising suggests.
But while they’re strictly replacement tires for now, this type of tire could eventually open an entirely new segment of original equipment. If four run-flats weigh less than five conventional tires, automakers will consider the potential for fuel savings, along with eliminating the cost of a spare rim and rubber. While they’re just starting out right now, such tires could possibly become the standard at some time in the future…and changing a tire will be as old-fashioned as cranking your car to start it.