Airless tires, non-pneumatic tires (NPT), or flat-free tires are

tire A tire (North American English) or tyre (Commonwealth English) is a ring-shaped component that surrounds a Rim (wheel), wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide Traction (engineeri ...

s that are not supported by

air pressure Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The Standard atmosphere (unit), standard atmosphere (symbol: atm) is a unit of pressure defined as , whi ...

. They can be used on small vehicles such as ride-on

lawn mower A lawn mower (also known as a grass cutter or simply mower, also often spelled lawnmower) is a device utilizing one or more revolving blades (or a reel) to cut a lawn, grass surface to an even height. The height of the cut grass may be fixed by ...

s and motorized golf carts. They also are used on heavy equipment required to operate on sites where risk of tire punctures is high. Tires composed of closed-cell polyurethane foam are also made for

bicycle A bicycle, also called a pedal cycle, bike, push-bike or cycle, is a human-powered transport, human-powered or motorized bicycle, motor-assisted, bicycle pedal, pedal-driven, single-track vehicle, with two bicycle wheel, wheels attached to a ...

s and

wheelchair A wheelchair is a mobilized form of chair using two or more wheels, a footrest, and an armrest usually cushioned. It is used when walking is difficult or impossible to do due to illnesses, injury, disabilities, or age-related health conditio ...

Advantages & disadvantages

The main advantages of airless tires is that they do not go flat and need to be replaced less frequently. Heavy equipment outfitted with airless tires will be able to carry more weight and engage in more rugged activities. Airless tires generally have higher

rolling resistance Rolling resistance, sometimes called rolling friction or rolling drag, is the force resisting the Motion (physics), motion when a body (such as a ball, tire, or wheel) Rolling, rolls on a surface. It is mainly caused by Plasticity (physics), non- ...

and provide somewhat less suspension than similarly shaped and sized pneumatic tires. Other problems for airless heavy equipment tires include dissipating the heat buildup that occurs when they are driven. Airless tires are often filled with compressed

polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...

s (plastic) rather than air, or can be a solid molded product. Airless tires are attractive to cyclists, as

bicycle tire A bicycle tire is a tire that fits on the Bicycle wheel, wheel of a bicycle or similar vehicle. These tires may also be used on tricycles, wheelchairs, and handcycles, frequently for Wheelchair racing, racing. Bicycle tires provide an importa ...

s are much more vulnerable to punctures than motor vehicle tires. The drawbacks to airless tires depend on the use. Heavy equipment operators who use machinery with solid tires may become fatigued. Any airless tire will be heavier than the rubber tire it is meant to replace. However, airless tires are not popular with hardcore off-roaders, as those vehicles often need to travel long distances at highway speeds. At speeds above 80 km/h, they can be unstable, causing severe vibrations (and passenger discomfort), and therefore potential for drivers to lose vehicle control. Installation of airless tires depends on the use. Heavy equipment will need special equipment to mount, but an airless bicycle tire can be mounted with little effort. Solid airless lawnmower tires come pre-installed on the wheel, allowing quick installation.

Examples

Many

bicycle-sharing system A bicycle-sharing system, bike share program, public bicycle scheme, or public bike share (PBS) scheme, is a shared transport service where bicycles are available for shared use by individuals at low cost. The programmes themselves include both ...

s use these tires to reduce maintenance. In 1938, J. V. Martin in the United States invented a safety tire with hoops of hickory encased in rubber and fitted with criss cross spokes of ribbed rubber. It could drive over blocks when tested in a springless test car. In 2005,

Michelin Michelin ( , ), in full ("General Company of the Michelin Enterprises P.L.S."), is a French multinational tyre manufacturing company based in Clermont-Ferrand in the Auvergne-Rhône-Alpes '' région'' of France. It is the second largest t ...

started developing an integrated tire and wheel combination, the " Tweel" (derived from "tire" and "wheel," which are combined into one new, fused part), which operates entirely without air. Michelin claims its "Tweel" has load carrying, shock absorbing, and handling characteristics that compare favorably to conventional pneumatic tires. However, the tire has a lot of vibration when driving over . Therefore the tire is only available for golf carts, ATV's and skid steer vehicles. In 2019 however Michelin and GM announced their goal of making a new airless tire for passenger vehicles available in 2024. The automotive engineering group of the mechanical engineering department at

Clemson University Clemson University () is a Public university, public Land-grant university, land-grant research university near Clemson, South Carolina, United States. - The blue-shaded pattern denotes university property. This shows Clemson University is ''out ...

is developing a low energy loss airless tire with Michelin through the NIST ATP project. Resilient Technologies and the University of Wisconsin–Madison's Polymer Engineering Center are creating a "non-pneumatic tire", which is a round polymeric honeycomb wrapped with a thick, black tread. The initial version of the tire is for the

Humvee The High Mobility Multipurpose Wheeled Vehicle (HMMWV; colloquial: Humvee) is a family of Military light utility vehicle, light, four-wheel drive Military vehicle#Military trucks, military trucks and utility vehicles produced by AM General. It ...

and is expected to be available in 2012. It is also the first group to make a commercially available mass-produced airless tire after its acquisition by Polaris, albeit only as coupled with their vehicle. The tire trademark is "Terrainarmor".

Bridgestone is a Japanese multinational manufacturing company founded in 1931 by Shojiro Ishibashi (18891976) in the city of Kurume, Fukuoka Prefecture, Fukuoka, Japan. The name Bridgestone comes from a calque translation and transposition of (), meaning ...

is developing the Bridgestone Air-Free Concept Tire, which can hold per tire. The Energy return wheel (ERW) has the outer edge of the tire connected to the inner rim by a system of springs. The springs can have their tension changed to vary the handling characteristics. Hankook is developing the iFlex airless tire. However, many tire manufacturing companies are yet to start making airless tire due to different limitations. Major companies like Goodyear say its airless tires won't be road-ready until 2030.

References

{{Emerging technologies, transport=yes Tires Automotive technologies

Advantages & disadvantages

Examples

See also

References