Non-pneumatic tires (NPT), or Airless 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 a risk of tire punctures is quite high. Tires which are composed of closed-cell polyurethane foam are also made for bicycles and wheelchairs.
The main advantage of airless tires is that they cannot go flat.
Airless tires in the past have had a have higher rolling resistance and provide much less suspension than similarly shaped and sized pneumatic tires. Other problems for airless tires in earlier days included dissipating the heat buildup that occurs when they are driven. Airless tires are often filled with compressed polymers (plastic), rather than air. However, new technology has come to the rescue and made quite a difference here these days.
Airless tires are attractive to cyclists, as bicycle tires are much more vulnerable to punctures than motor vehicle tires. However users of airless bicycle tires have complained of difficulty of mounting the tires on wheel rims (caused by tight tires) or tires slipping\rolling on rim when in use (caused by loose tires). Other common complaints are increased rolling resistance, increased wheel weight and a harsh ride (leading to rider fatigue and broken spokes). These are issues especially for mountain bike riders, but is not an issue in heavy industrial applications.