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Beware of Run-Flat Tires

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7/24/2007 - New York
Beware of Run-Flat Tires

by Stephan Wilkinson http://www.concierge.com/cntraveler/blogs/perrinpost/2007/07/beware-of-run-f.html

Don't believe the hype about run-flat tires. Tire companies -- and the car companies that sell them as an option -- would love you to believe that run-flats make you immune to punctures and blow-outs. The truth is that expensive, rough-riding, fast-wearing, short-lived run-flats allow you to drive maybe 50 miles after a puncture, at a poky maximum of 50 mph.



And you'd better pray that somewhere within that 50 miles is a car dealer or a very well-equipped tire retailer with the expensive special equipment needed to dismount your run-flat, and hope that he also has a replacement for your tire. (Run-flats often can't be repaired but must be replaced, and they can cost half again as much as the equivalent conventional tire.) If you're road-tripping in rural Wyoming or northern Michigan, say, you could be stuck overnight while your car is flat-bedded to a dealer and a replacement located and shipped.

Here's why I'm wary of run-flats:

Run-flats have either such stiff sidewalls that they'll support the weight of the car even if there's no air in the tire, or a solid, wheel-like insert that supports the car when the tire itself no longer can. Either way, the tires are impossible to remove from the wheel with conventional tire-dismounting equipment. (A third type of new-tech tire has a puncture-sealing layer inside the tread area that quickly oozes into and seals small leaks; it's not intended to run flat but instead to never go flat.)

Stiff sidewalls can make a car's ride harsh and uncomfortable, and some run-flats also have turned out to be unpleasantly noisy. Run-flats are heavier than standard tires and thus add "unsprung weight" to a car, which is detrimental to handling.

An ordinary tire can be removed, repaired, and remounted by the most junior mechanic at any one-pump service station in the country. And if the flat tire has a damaged sidewall and needs to be replaced, like-size new tires are widely available even in small towns for all but exotic high-performance rubber.

BMW owners, particularly, complain about run-flats. In fact, the only people who really like them are the engineers who design new cars. Spare tires have long been an automotive albatross -- heavy, space-consuming, and often unused throughout the life of the car. Eliminate the spare and you have room for a bigger trunk or for fold-flat seats in a van or SUV, and the car is a little lighter, which means better gas mileage. After all, the spares for some big SUVs are large and heavy enough that only a weightlifter could mount one in place of a jacked-up flat tire.

Run-flat technology will someday actually make spares superfluous, but it isn't there yet. Run-flats have, on some cars, exhibited damaging wear patterns that have ruined the tires prematurely, have proven to be more susceptible to tread damage, and are substantially more expensive than equivalent standard rubber. And sometimes, opting to replace them on a new car with conventional rubber adds even more expense: You'll need new wheels, and you'll have to buy the jack and lug wrench that those weight-conscious engineers never put in your trunk.

If you have any questions or comments regarding this article please contact Mark Farkhan at This e-mail address is being protected from spambots. You need JavaScript enabled to view it


 

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