There are three basic technologies currently available, described below.
Self-supporting run flat tires are fairly common on light trucks and passenger cars and typically provide for the vehicle to drive for 50 miles at around 50 miles per hour. However, if the tires are treated to this kind of punishment, they may still be irreparably damaged in the process. In addition, if the tire is punctured in the sidewall or at the edge of the tread, repair may be impossible or unsafe.
The first vehicle ever to be sold with run-flat tires was the Mini 1275GT in July 1974. It used the Dunlop Total Mobility Tyre (abbreviated to TMT, later known as Denovo) system which required special wheels and featured ultra-low profile side-walls.
In recent versions of the Chevrolet Corvette (C5 and C6), run flat tires are required as there is no accommodation made for a spare tire. As a spare wheel is optional on the MINI One and Cooper and non-existent on the Cooper S and One Diesel, the new MINI also makes use of run flat tires for certain wheel sizes, as do many BMW models.
Self-supporting run flat tires typically carry a 15% - 27% weight penalty over similar standard tires, or additional 2-3 kg (4-7 lb) (samples based on 225/45-17 tires). The additional mass concentrated on the outer edge of the wheels can impose a significant performance penalty due to greater rotational and unsprung mass.
There are also a number of retro-fitted tire sealants which act in a similar way to self-sealing tires. These compounds are normally injected through the tire valve. The rotating force then distributes the compound onto the inner surface of the tire to act as a self-sealing lining within the tire.
Depending on the design, some run-flat tires perform better than regular tires, and some slightly worse. Some run-flat tires have a 20% higher rolling resistance, in part due to their added structural material and mass; this can worsen a vehicle's fuel efficiency. On the other hand, internal bracing in some run-flat tires reduces deformation, with the opposite effects of reducing rolling resistance and improving fuel efficiency. Also, the overall weight increase of the tires may be offset in a vehicle by the elimination of a spare tire and tire jack. Some manufacturers by 2001 had mandated that run-flat tires provide low rolling-resistance for improved fuel-efficiency, a soft ride, and excellent wet handling.
Makers of run flat tires as well as the automobile manufactures that use them for new cars have come under fire for not fully disclosing some of the significant downsides of many run flat tires, including the significantly shorter life of a typical run flat tire (often as few as 10,000 miles versus approximately 40,000 miles for a conventional tire), the significantly higher cost to repair (sometimes as high as $900 per tire, but typically at least $350 per tire versus $125 for a typical family car tire) and the extreme shortage of both replacement tires and trained repair facilities (there are typically only a handful of authorized repair shops in each major metropolitan area in the US). Michelin and Honda have been named in a lawsuit citing various forms of product misrepresentation (read the press release).
Another criticism is that often cars with run flats do not have a spare tire. Manufacturers like BMW do have space for a spare in some of their models (the 5 series for example) but do not include a spare, presumably to save money.
Run-flat tires accounted for less than 1% of replacement tire sales in the U.S. in 2005. They are gaining in popularity with vehicle manufacturers as a consumer option, and it is expected that this will increase the share of replacement sales in the future.
Publication No. WO/2009/080587 Published on July 2, Assigned to Societe de Technologie Michelin, Michelin Recherche et Technique for Run-Flat Tyre (French Inventor)
Jul 04, 2009; GENEVA, July 4 -- Francois Hottebart, France, has developed a run-flat tyre with a crown. The patent has been assigned to Societe...