How Run-flat Tires Work

What's wrong with a blowout every now and then?
A Goodwrench technician checks the wheels and tires with a Tire Pressure Monitoring Systems (TPMS) tool.
A Goodwrench technician checks the wheels and tires with a Tire Pressure Monitoring Systems (TPMS) tool.

Despite run-flats' obvious benefits, they also have a few serious compromises that should be considered before buying a new car.

Since the structure of run-flats is a little different than other types of tires, they might not provide the kind of driving experience you're used to (especially if you take your car's speed or brawn seriously). Because a very stiff sidewall is essential to their function, run-flats tend to provide a rather harsh ride because they provide less cushion from the road. Run-flats can't provide a wide selection of specialized tread types either, like those popular for sport driving or occasional off-roading; Consumer Reports says that even drivers who are okay with the compromise have said that run-flats' tread sometimes lacks in basic capabilities [source: Consumer Reports]. They're also heavier than regular tires, which reduces your car's overall efficiency.

After a run-flat is punctured, its performance potential is further compromised. Of course, its primary purpose is to get your car to safety, so as long as you aren't faced with a dangerous situation, the tire did its job. A damaged run-flat isn't going to be exactly comfortable, but it's designed that way. It's important to understand that a run-flat tire isn't designed to be driven like that forever -- it needs to be replaced as soon as possible.

When you finally make it to your mechanic or tire shop to replace your blown-out run-flat, be prepared for potential sticker shock: Run-flats typically cost considerably more than their traditional counterparts. And since the tread tends to wear down faster, you might be faced with the wallet-busting plight of replacing all four corners long before you'd expected. Another potential roadside shock for car owner's with run-flat tires: Most cars originally equipped with run-flats don't come with a spare in the trunk -- a can of liquid fix-a-flat and a small air compressor is a common substitute.

And one final consideration if you're making a decision about investing in run-flats: A puncture in a run-flat tire generally can't be repaired, whereas a regular tire can often be saved with an inexpensive plug. However, after run-flats become the norm, most people will probably never learn how to change a tire anyway.

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