World Library  
Flag as Inappropriate
Email this Article

Run-flat tire

Article Id: WHEBN0003545630
Reproduction Date:

Title: Run-flat tire  
Author: World Heritage Encyclopedia
Language: English
Subject: Flat tire, Spare tire, Tire, Volvo YCC, Outline of tires
Collection: Tires, Vehicle Technology
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Run-flat tire

Michelin PAX run-flat wheel

A run-flat tire is a pneumatic vehicle tire that is designed to resist the effects of deflation when punctured, and to enable the vehicle to continue to be driven at reduced speeds (up to 55 mph (90 km/h)), and for limited distances of up to 100 mi (160 km), or even 200 mi (320 km) depending on the type of tire.

Contents

  • Technologies 1
    • Self-supporting 1.1
    • Self-sealing 1.2
    • Auxiliary-supported 1.3
    • Standards of performance 1.4
    • Market share 1.5
    • Factors contributing to small market share 1.6
  • See also 2
  • References 3

Technologies

There are three basic technologies currently available, described below.

Self-supporting

The origins of the commercial self-supporting run-flat tire started in 1935 with a tire that had a fabric inner tire. The tire was advertised as a protection against blow outs, a common and dangerous occurrence in the 1930s.[1]

In 1934, Michelin introduced a tire that was based on technology developed for local commuter trains and trolleys. It had a safety rim inside the tire which if punctured would run on a special foam lining. The tire was sold for military use and for specialized vehicles like bank armoured cars. It was advertised as "semi-bullet proof". While the tire performed as advertised it was far too expensive to be a feasible option for most private automobile users.[2]

In 1958, Chrysler teamed with Goodyear Tire and Rubber Company to offer Captive Air run-flat tires using an interlining to carry the weight.

In 1972 Dunlop launched the Denovo "fail-safe" wheel and tire system that became optional equipment on the Rover P6 3500 in 1973,[3] and by 1983 evolved into the TD/Denloc which became standard equipment across the whole Austin Metro range.

Most recently, Bridgestone and Pirelli run-flat tires are supplied on some new model BMW cars. The automaker promoted these as a safety feature and as an alternative to carrying a spare tire.

Self-supporting run-flat tires are now common on light trucks and passenger cars and typically provide for the vehicle to drive for 50 miles (80 km) at around 50 miles per hour (80 km/h). However, if the tires are subject to this kind of misuse, they may become 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. These tires carry a 20 to 40 percent weight penalty over similar standard tires.[4] The thicker sidewall also means higher rolling resistance, thus reducing the vehicle's fuel economy.[4]

Self-sealing

These tires contain an extra lining within the tire that self-seals in the event of a small hole due to a nail or screw. In this way, the loss of air is prevented from the outset such that the tire is either permanently self-repairing or at least loses air very slowly.

There are also a number of retrofitted 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.

Auxiliary-supported

Run-flat tire with support ring

In this system, there is an additional support ring or insert attached to the wheel that can support the weight of the vehicle in the event of a loss of pressure. These systems generally offer better ride quality because they can be placed inside a standard tire. The runflat insert, because of its unsurpassed ability to carry heavy vehicle loads for long distances at high speeds, is the normal runflat selection for military vehicles, high-level executive protection vehicles, and "armored" vehicles used by government, aid groups, or private contractors in conflict zones.

Standards of performance

The basic benefit of using run-flat tires is continued mobility in case of a loss of air pressure, either due to a 'normal' puncture or a hostile deliberate act or even a bullet shot while the vehicle is travelling at high speed. Performance criteria are therefore in terms of distance and speed at which the vehicle can escape without becoming immobile and the steering control over the vehicle during this process.

The usual standard of performance, especially for military or security vehicles, are the Finabel standards.

Market share

Run-flat tires accounted for less than 1% of replacement tire sales in the U.S. in 2005. In 2006, it was expected that such tires would gain popularity with armored vehicle manufacturers, but growth figures were slow with one major model, the Michelin PAX System, no longer being developed by the manufacturer (though replacements will be produced for the foreseeable future).[5] A Michelin study released in 2008 found that 3 percent of drivers worldwide want run-flat tires. U.S. market share is well below 1 percent. American Honda Motor Co. announced that the 2009 Honda Odyssey Touring and Acura RL were its last models available with run-flat tires and with Honda no longer using run-flats. This leaves only a handful of volume manufacturers offering them as standard fittings and only on some models. An exception is BMW, who are the largest fitter of run-flats as original equipment.[4]

Factors contributing to small market share

Besides the cost, which can be more than double other tires of comparable size, run-flat tires can not be run flat if the flat is due to sidewall damage, a common cause of flats. Also, under the best circumstances, the speed and range that the run-flat tires can be run flat is very limited. Run-flat tires cannot be driven over 50 miles per hour and usually offer only up to 50 miles of extended mobility. These limitations lower the value of the extra expense for many buyers. In certain applications, depending on the vehicle and specific tire design, a run-flat tire can provide from 25 miles to 200 miles driving while flat with limited speed.

See also

References

  1. ^ "Fabric Inner Tube Lessens Blowout Hazards". Popular Mechanics 63 (4): 488. April 1935. Retrieved 10 June 2012. 
  2. ^ "Bullet Proof Tire Has Sponge Rubber Tube". Popular Mechanics 62 (6): 872. December 1934. Retrieved 10 June 2012. 
  3. ^ Scottish Evening Times, 30 May 1973, p. 2
  4. ^ a b c Kranz, Rick (27 July 2009). "The air runs out of run-flat tires". The Center for Auto Safety. Retrieved 10 June 2012. 
  5. ^ Jensen, Christopher (20 April 2008). "Michelin Giving Up on PAX Run-Flat Tire". The New York Times. Retrieved 2 July 2010. 
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.