Run Flat Tire

Information about Run Flat Tire

A run-flat tire is a pneumatic vehicle tire that is designed to resist the effects of deflation and to enable the vehicle to continue to be driven, although depending on the type of tire, at reduced speeds (i.e. 80 km/h or 50 mph) and for limited distances. They were originally developed for two-seat sports cars with little room for spare tires and jacks, but are growing in popularity for other vehicles because of their safety and convenience.^[1]

Technologies

There are three basic technologies currently available, described below.

Self-supporting

The tire is built with stiffer side-walls that can bear the weight of the vehicle even when the pressure within the tire is greatly reduced. The side-walls are typically constructed of layers of rubber and a heat-resistant cord that prevent the side-walls from folding or creasing. The bead around the edge of the tire is also specialized to grip the wheel rim such as to avoid becoming detached from the rim.

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.^[2] As a spare wheel is optional on the Mini Cooper and non-existent on the Cooper S and ONE Diesel, the new MINI also makes use of run flat tires, as do many BMW models.<ref name="msn" />

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.

Self-sealing

See also: Self-sealing fuel tank

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 ted 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.^[3]

Auxiliary-supported

In this system, there is an additional support ring attached to the wheel that can support the weight of the vehicle in the event of a loss of pressure. While these systems generally offer better ride quality because their sidewall's stiffness can be equivalent to a standard tire, the requirement to have both special wheels and special tires increases cost and limits these systems from widespread use.

Performance characteristics

Run-flat tires typically have a 20% higher rolling resistance, in part due to their added structural material and mass. This can worsen a vehicle's fuel efficiency.<ref name="trb" /> Internal bracing in some run-flat tires reduces deformation, which in turn reduces rolling resistance. The overall weight increase of the tires may be offset in a vehicle by the elimination of a spare tire and tire jack.

Market share

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.<ref name="trb" />

External links

The Michelin PAX auxiliary supported run flat system
The Pirelli Self-Supporting Run Flat Technology
How Stay-A-Flate works - Description of retro-fitted liquid tire sealant

Sources

Tire Tech: Run Flat Tires (Commercial website). The Tire Rack. Retrieved on 2007-08-12.

1. ^ "Tires and Passenger Vehicle Fuel Economy: Informing Consumers, Improving Performance -- Special Report 286.". National Academy of Sciences, Transportation Research Board, 2006. Retrieved on 2007-08-11.
2. ^ Run-Flat Tires: A New Standard Rising. (News website). MSN Retrieved on 2007-08-12.
3. ^ How Stay-A-Flate Works (Commercial website). Stayaflate. Retrieved on 2007-08-12.

Pneumatics is the use of pressurized air to effect mechanical motion. Pneumatics is employed in a variety of settings. In dentistry applications, pneumatic drills are lighter, faster, and simpler than an electric drill of the same power rating (because the prime mover, the compressor, is
..... Click the link for more information.

Vehicles are non-living means of transport. They are most often man-made (e.g. bicycles, cars, motorcycles, trains, ships, and aircraft), although some other means of transport which are not made by man can also be called vehicles; examples include icebergs and floating tree trunks.
..... Click the link for more information.

Tires or tyres (see American and British English spelling differences) are pneumatic enclosures used to protect and enhance the effect of wheels.

Tires are used on all types of vehicles, from cars to earthmovers to airplanes.
..... Click the link for more information.

Deflation is a decrease in the general price level over a period of time. Deflation is the opposite of inflation. For economists especially, the term has been and is sometimes used to refer to a decrease in the size of the money supply (as a proximate cause
..... Click the link for more information.

Kilometres per hour (American English: kilometers per hour) is a unit of both speed (scalar) and velocity (vector). The unit symbol is km/h or kmÂ·h⁻¹
..... Click the link for more information.

Miles per hour is a unit of speed, expressing the number of international miles covered per hour.

Miles per hour is the unit used for speed limits, and speeds, on roads in the United Kingdom, United States and some other nations, where it is commonly abbreviated in everyday
..... Click the link for more information.

Mini is a small car that was produced by the British Motor Corporation (BMC) and its successors from 1959 to 2000. The most popular British-made car, it has since been replaced by the New MINI which was launched in 2001.
..... Click the link for more information.

Dunlop Tyres was an international United Kingdom-based company founded in 1888 by John Boyd Dunlop after he invented the modern pneumatic inflatable tyre. Its first factory opened in Dublin in 1889.
..... Click the link for more information.

Chevrolet Corvette is a sports car that has been manufactured by Chevrolet since 1953. It is built today at a General Motors assembly plant in Bowling Green, Kentucky, but in the past it was built in Flint, Michigan and St. Louis, Missouri.
..... Click the link for more information.

Bayerische Motoren Werke AG

Aktiengesellschaft
Founded 1916
Headquarters Munich, Germany

Key people Dr. Norbert Reithofer, Chairman and CEO
Industry Automotive
Products Automobiles
Motorcycles
Revenue €49 billion (2006)
..... Click the link for more information.

unsprung weight (or, more properly, the unsprung mass) is the mass of the suspension, wheels or tracks (as applicable), and other components directly connected to them, rather than supported by the suspension.
..... Click the link for more information.

In aviation, self-sealing fuel tanks are a fuel tank technology that saw widespread use during World War II, when it quickly became apparent that fighter aircraft lacked adequate protection.
..... Click the link for more information.

nail is a pin-shaped, sharp object of hard metal, typically steel, used as a fastener. Nails for specialised purposes may also be made of stainless steel, brass or aluminium.
..... Click the link for more information.

screw is a shaft with a helical groove or thread formed on its surface and provision at one end to turn the screw. Its main uses are as a threaded fastener used to hold objects together, and as a simple machine used to translate torque into linear force.
..... Click the link for more information.

sealant is a viscous material that changes state to become solid, once applied, and is used to prevent the penetration of air, gas, noise, dust, fire, smoke or liquid from one location through a barrier into another.
..... Click the link for more information.

valve is a device that regulates the flow of substances (either gases, fluidized solids, slurries, or liquids) by opening, closing, or partially obstructing various passageways. Valves are technically pipe fittings, but usually are discussed separately.
..... Click the link for more information.

Rolling resistance, sometimes called rolling friction or rolling drag, is the resistance that occurs when an object such as a ball or tire rolls. It is caused by the deformation of the wheel or tire or the deformation of the ground.
..... Click the link for more information.

Tweel (a portmanteau of tire and wheel) is an experimental tire design being developed at Michelin. The tire uses no air and therefore cannot burst or become flat. Instead, flexible polyurethane spokes are used to support an outer rim.
..... Click the link for more information.

Pneumatic tires are manufactured according to relatively standardized processes and machinery, in around 450 tire factories in the world. Over 1 billion tires are manufactured annually, making the tire industry the majority consumer of natural rubber.
..... Click the link for more information.

A tire pressure monitoring system (TPMS) is an electronic system to monitor the air pressure inside a pneumatic tire. They are sometimes referred to as remote tire pressure monitoring systems (RTPMS) or simply as Run flat indicators.
..... Click the link for more information.

20th century - 21st century - 22nd century
1970s 1980s 1990s - 2000s - 2010s 2020s 2030s
2004 2005 2006 - 2007 - 2008 2009 2010

2007 by topic:
News by month
Jan - Feb - Mar - Apr - May - Jun
..... Click the link for more information.

This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.

Herod_Archelaus