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.

Author's Note: How Run-flat Tires Work

I had my laptop open to write this article and had the TV on, too, which is unusual. I never watch TV. I never change tires, either.

But "A Christmas Story" was on, so I decided it was time for my annual indulgence. And I'd forgotten about the "f-bomb" scene -- Ralphie's ill-fated attempt to help the old man change a flat. It was a minor inconvenience, like running low on gas, so I guess people must have gotten good at it. When Ralphie was describing his father's tire-changing prowess, I realized, no one ever changes tires anymore, do they? I can't remember the last time I was in a car that got a flat, or even saw someone with a car on a jack stand on the side of the road. Tires must have gone flat a lot more often back then, and not just because we have run-flats now. Wheels aren't rounder now, right? And I'd find it hard to believe that roads are smoother. Maybe tires aren't universally better, though. Maybe everyone just uses their cellphones to call for roadside assistance -- something Ralphie and his father couldn't do in 1940s Indiana.

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Sources

  • Consumer Reports. "Tire Buying Guide." Oct. 15, 2012. (Dec. 19, 2012) http://www.consumerreports.org/cro/tires/buying-guide.htm
  • Goddard, Nick. "How Tony Stewart's NASCAR Tech Trickles Down to Your Car." Popular Mechanics. July 2, 2012. (Dec.19, 2012) http://www.popularmechanics.com/cars/news/vintage-speed/how-tony-stewarts-nascar-tech-trickles-down-to-your-car-10251068
  • State Farm. "Run Flat Tires; Pros and Cons." June 27, 2011. (Dec. 19, 2012) http://learningcenter.statefarm.com/auto/run-flat-tires-the-pros-and-cons/
  • Tire Rack. "Tire Tech Information -- Run-Flat Tires." (Dec. 19, 2012) http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=56

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