Airless tires, non-pneumatic tires (NPT), or flat-free tires are tires that are not supported by air pressure. They are used on some small vehicles such as riding lawn mowers and motorized golf carts. They are also used on heavy equipment such as backhoes, which are required to operate on sites such as building demolition, where risk of tire punctures is high. Tires composed of closed-cell polyurethane foam are also made for bicycles and wheelchairs. They are also commonly found on wheelbarrows which may be used for yard work or construction.
The main advantage of airless tires is that they do not go flat. Other advantages are that airless tires need to be replaced less, resulting in savings. 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 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 polymers (plastic), rather than air or can be a solid molded product.
Airless tires are attractive to cyclists, as bicycle tires 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 will complain of fatigue whereas lawn mowers that use solid or airless tires have no drawbacks. Bicycle riders who use airless tires may complain that the tire is harder than a comparable pneumatic tire.
Only anecdotal evidence exists that airless tires may cause broken spokes on a bicycle wheel. Any airless tire will be heavier than the rubber tire it is meant to replace; however, many rubber pneumatic tires are also heavy. Rubber tires vary in rolling resistance and an airless tire or solid insert may only marginally increase rolling resistance if at all.
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 or no effort. Solid airless lawnmower tires come pre-installed on the wheel allowing quick installation.