A flat tire often happens at the most inopportune time or place. Most people may call roadside assistance, but they’ll likely be waiting about 45 minutes to an hour. If you know how to change the spare, it’s a dirty job and chances are you’re not properly dressed for it. Worse yet, your car may have no spare tire, and you might not know how to use the tire repair kit.
Run-flat tires are built with very stiff sidewalls, enough so that if the tire loses pressure, the sidewalls will support the weight of the car. This can prevent loss of control caused by a blowout, for instance, and allows for continued driving until a repair can be accomplished in safety.
- You can drive on a flat tire: The primary benefit of a self-supporting tire is that it allows you to keep driving on a flat about 100 miles after all the air has gone. You don’t have to get out of the car in the cold, or the rain, or onto a busy highway. Drivers will usually have to reduce speed to about 50 mph to get the maximum range. The owner’s manual will have exact figures for each tire/vehicle application.
- Better stability after a blowout: Because this tire can support the vehicle for miles without air, a sudden deflation results in less weight transfer and tread destabilization. Steering and handling will remain near normal.
- Lower vehicle weight: With the spare wheel and tire repair tools eliminated, vehicle weight should theoretically go down. But it won’t be as much as you might expect since run-flats weigh more than regular tires due to the added sidewall reinforcement.
- No spare: Vehicles equipped with run-flats do not carry a spare wheel and tire, which means they don’t have a jack or tools either. In fact, eliminating the spare tire and reallocating that space to some other purpose (styling, a third-row seat, interior room, etc.) is a big reason why carmakers offer run-flats.
- Reduced tread wear: A 2013 study by J.D. Power found that people replaced their run-flat tires an average of 6,000 miles sooner than owners using conventional tires. Opinions differ on the reason, but one theory is that tiremakers put a soft tread compound on a run-flat tire to counter the hard ride. A side effect of the softer compound is a shorter tread life.
- Blowouts are still possible: If a driver fails to heed or notice the warnings and drives beyond the zero-pressure range or above the speed limitation, the tire can begin to disintegrate, with the same destabilizing effects. Additionally, if the puncture occurs on the sidewall or if the tire hits a large object, the driver will have to call a tow truck. The J.D. Power study found that “customers with vehicles equipped with run-flat tires are nearly twice as likely as those with vehicles equipped with conventional tires to have to replace a tire due to a flat or blowout.”
- Hard to tell if it is low on air: The side effect is that the sidewalls do not bulge if the air pressure is low. Therefore, it is critical to have a tire pressure monitoring system and check your tire pressure frequently. Otherwise, you’ll never know when you have a flat.
- Harsher ride: The stiff sidewalls that make a run-flat work also result in a harsher ride. If the vehicle came with run-flat tires from the factory, the automaker usually tunes the suspension to offset the rougher ride.
- Cost: Run-flat tires are more expensive to replace. Also, many run-flats cannot be repaired and often need to be replaced in pairs.
- Less on-shelf availability: Because run-flats aren’t a big-selling tire, drivers shouldn’t expect to roll into just any tire shop and buy them. It may be easier to do so in larger cities, but if you’re a run-flat user on a road trip and get a flat near a small town, you’ll probably have to make a detour to find a suitable new tire. Or worse, you may have to stay overnight, waiting for the tire to be shipped.
Based on the pro and cons above, run-flat tires seem to have more downsides than upsides, but many people swear by them. My advice has always been that run flats tires are just not worth the hassle, the performance hit, and the expense. The best way of handling a deflation of a run-flat tire is precisely the same as a conventional tire – pull over as soon as possible and change the tire for the spare to avoid having to replace the tire, but car manufacturers have largely made that impossible. Runflats just doesn’t offer enough advantages to offset all the problems. Take time to read customer reviews and know what tires come standard on a car before you buy.