Everything You Should Know Before Buying Run-Flat Tires

Run-flat tires are very different than conventional tires. They may look similar from the outside, but there's a world of innovation inside. Unlike standard rubber, run-flat tires or zero-pressure tires have reinforced sidewalls to support the vehicle's weight even after a complete loss of air pressure (via Bridgestone). Of course, what this means is you can continue driving at a predetermined speed and distance after a puncture, allowing you to reach a workshop or service center and change the tire. Bridgestone points out that its run-flats, for example, can drive up to 50 miles at a maximum speed of 50 miles per hour. 

This all sounds fine and dandy, but there are tradeoffs to consider with run-flat tires. Before spending your hard-earned cash on a brand-new set of run-flats, here is everything you need to know about run-flat tires in general, including their pros and cons and what to look out for.

How do run-flat tires work?

There are two general types of run-flat tires: Self-supporting and self-sealing (via in2tires). The former utilizes a stiffer and reinforced sidewall construction to support the vehicle after losing air pressure. Meanwhile, the latter features a thin layer of sealant that helps maintain air pressure after a puncture, in2tires notes, pointing out that self-sealing run-flat tires still need air to operate correctly, while self-supporting run-flats can keep you going even after losing all air pressure.

The Drive explains that the most common run-flat tire you can buy is the self-supporting tire, although manufacturers like Pirelli and Continental are now offering self-sealing run-flat tires. You can identify a run-flat tire by visually inspecting the sidewall. Depending on the brand, run-flat tires will have RFT (Run-Flat Tire), SSR (Self-Supporting Run-Flat), EMT (Extended Mobility Tire), or ZP (Zero Pressure) markings, according to Toee Tire.

Run-flat tires are not compatible with any vehicle. Only vehicles that came with run-flats from the factory can use run-flat tires. Besides having a standard TPMS, new cars with standard run-flats have particular changes to the suspension and chassis to accommodate those special tires — otherwise, Family Handyman notes, the tires may unexpectedly separate from the wheel bead. If your vehicle originally came with run-flat tires, it is possible to replace them and mount conventional tires instead, as Firestone explains. Remember that OEM run-flat vehicles do not have tire-changing tools and a spare tire in the trunk, so keep this in mind before making the switch.

How long can I drive with a punctured run-flat tire?

Regular tires need air to support the weight of your vehicle. Bridgestone notes that run-flat tires are no different in this regard, but everything changes when the tire gets a puncture. With a regular tire, your car is immobile until the tire is changed. But with run-flats, you can continue driving presumably enough to get you home or to the nearest garage, Bridgestone explains.

Another common question is how to know if your run-flat tires have a puncture. Since run-flats would still look inflated even with zero air pressure, it may be tricky to know if your run-flats are punctured or losing air. It's the reason run-flat tires are only compatible with vehicles that come standard with a tire pressure monitoring system (TPMS) from the factory, as Bridgestone noted. You will also feel a thud and a vibration, according to Bike Hike.

Tire manufacturers use the same materials from common tires in making a run-flat tire, so the wear rates should be comparable, though a J.D. Power study noted by Edmunds found that some users replace their run-flats up to 6,000 miles sooner. Don't ignore the low tire pressure warning sign, which lights up if the tire needs air. Even though run-flat tires can operate without air, as Bridgestone noted, keeping the correct tire pressure at all times will ensure steady rolling resistance and longer wear life.

Run-flat tires: The pros and cons

Run-flat tires are far from perfect. Here are the pros and cons to consider before taking the plunge, as noted by Edmunds.

First, the pros. Run-flats allow you to keep driving with a flat tire. Thanks to their heavily reinforced sidewalls, run-flats are more stable after a tire blowout, allowing you to steer and handle the vehicle safely during sudden deflation, as we covered above. Run-flats will eliminate the need to carry heavy items like a jack, a spare tire, and other tools in the trunk because you can drive home or to a repair shop. 

Here are the cons, beginning with the price. Each run-flat tire typically costs 25% more than a regular tire, per Automotive Fleet. You cannot repair a run-flat tire after a puncture. Run-flat tires weigh more than a conventional tire due to their reinforced construction, resulting in a harsher and noisier ride in most cases. Run-flats could also affect vehicle handling and braking due to their portly weight. Finding run-flat tires that fit your vehicle can be challenging, posing a significant problem if you encounter a flat in small cities or towns.

My run-flat tires are low on air. What should I do?

Adding air to a run-flat tire is no different from an ordinary tire, according to Driver Moola. Add air using an air compressor until each tire reaches the proper air pressure, preferably using a separate air pressure gauge. In the absence of a puncture, a lit TPMS warning sign means your run-flat tires are riding low on air. Remember that driving with underinflated tires — even if your car has run-flats — increases the potential for punctures and blowouts.

Whether your car has run-flats or not, make it a habit to check the tire pressure using an air pressure gauge at least once a week or whenever you fill up with gas. This is convenient because many gas stations have air stations. In addition, it's a good idea to check the tire pressures before embarking on a long trip, according to the experts at Bridgestone.

Is it safe to mix run-flat tires with ordinary tires?

No, according to Tire Rack. Unless specified by the manufacturer, you should never mix run-flats with ordinary tires unless in temporary emergencies. Additionally, you should avoid mixing different types or brands of run-flat tires in your car, its users suggest. That said, you can retrofit an older vehicle with run-flat tires, per Popular Mechanics. But you need to perform a couple of mods to make everything work perfectly. For instance, you need to install a tire pressure monitoring system or TPMS to know if your new run-flats are losing air. Depending on the make and model of your vehicle, installing run-flats could require a few suspension tweaks to counteract the stiffer sidewalls.

In general, run-flat tires are worth the extra cost. Run-flat tires offer better protection against blowouts while preventing you from dealing with a flat tire in precarious circumstances (like on the side of a busy highway during rush hour in heavy rain), as Bridgestone noted. Run-flat tires are not the holy grail of sporty handling or a comfier ride, but the peace of mind is definitely worth the added cost.