A flat tire (

British English British English (BrE, en-GB, or BE) is, according to Lexico, Oxford Dictionaries, "English language, English as used in Great Britain, as distinct from that used elsewhere". More narrowly, it can refer specifically to the English language in ...

: flat tyre) is a deflated

pneumatic tyre Pneumatics (from Greek ‘wind, breath’) is a branch of engineering that makes use of gas or pressurized air. Pneumatic systems used in industry are commonly powered by compressed air or compressed inert gases. A centrally located and elec ...

, which can cause the rim of the wheel to ride on the tire tread or the ground potentially resulting in loss of control of the vehicle or irreparable damage to the tire. The most common cause of a flat tire is puncturing of the tire by a sharp object, such as a

nail Nail or Nails may refer to: In biology * Nail (anatomy), toughened protective protein-keratin (known as alpha-keratin, also found in hair) at the end of an animal digit, such as fingernail * Nail (beak), a plate of hard horny tissue at the tip ...

or pin, letting the air escape. Depending on the size of the puncture, the tire may deflate slowly or rapidly.

Other causes

Besides puncturing of the tire a flat can be caused by: failure of or damage to the

valve stem A valve stem is a self-contained valve which opens to admit gas to a chamber (such as air to inflate a tire), and is then automatically closed and kept sealed by the pressure in the chamber, or a spring, or both, to prevent the gas from escaping ...

; rubbing of the tire against the road, ripping the tire, or separation of tire and rim by collision with another object; excessive wear of the tire

tread Tread may refer to: Arts and media * ''Tread'' (film), a 2019 American documentary film about Marvin Heemeyer * Tread (Transformers) * Tread, a character in the novel series '' Transformers: The Veiled Threat'' * Tread rap, subgenre of trap that b ...

allowing explosive tire failure or allowing

road debris Road debris, a form of road hazard, is debris on or off a road. Road debris includes substances, materials, and objects that are foreign to the normal roadway environment. Debris may be produced by vehicular or non-vehicular sources, but in all ...

to tear through it. Some tyres, particularly those with a slow leak, can be repaired and re-inflated; others, especially those with worn tread, must be replaced.

Driving or riding with a flat tire

Where a flat tire occurs, drivers are advised to slow gradually and pull off the road. Continuing to drive may damage the wheel, the hub or other parts of the vehicle. Driving with a flat tire, especially at high speeds, may result in a loss of control and possibly result in a car accident. On a bicycle, a flat tire will compromise handling, as well as increasing

rolling resistance Rolling resistance, sometimes called rolling friction or rolling drag, is the force resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface. It is mainly caused by non-elastic effects; that is, not all the energy nee ...

Flat tire repair

Motor vehicles

A UK source reports that flat tires account for about 10% of motor vehicle breakdowns. Motor vehicles are normally equipped for changing a tire. These tools include a

jack Jack may refer to: Places * Jack, Alabama, US, an unincorporated community * Jack, Missouri, US, an unincorporated community * Jack County, Texas, a county in Texas, USA People and fictional characters * Jack (given name), a male given name, ...

, a

tire iron A tire iron (also tire lever or tire spoon) is a specialized metal tool used in working with tires. Tire irons have not been in common use for automobile tires since the shift to the use of tubeless tires in the late 1950s. Bicycle tire irons ...

lug wrench A lug wrench also colloquially known as a tire iron, is the name for a type of socket wrench used to loosen and tighten lug nuts on automobile wheels. In the United Kingdom and Australia it is commonly known as a wheel brace. Lug wrenches may b ...

, and a

spare tire A spare tire (or stepney in some countries) is an additional tire (or tyre - see spelling differences) carried in a motor vehicle as a replacement for one that goes flat, has a blowout, or has another emergency. ''Spare tire'' is generally a mi ...

. Air pumps run by hand-lever, pressure cans, or electricity can be used to re-inflate slow-leaking tires. One common way to temporarily repair and re-inflate a punctured tire at the roadside is to use a canned tire sealant. The motorist attaches this to the valve, and the compressed propellant inside forces the can's contents through the valve into the tire, a liquid sealant is forced towards the puncture and will seal the puncture. The compressed propellant also inflates the tire. Tire sealant is typically useful on punctures of 3/16in. (5mm) diameter or less. According to research carried out by Continental Tires, 95% of punctures are caused by objects of 5mm or less. Typically, the sealant is a water based latex solution which can easily be removed by a tire repair professional before a permanent repair is made. Canned tire sealants are quick and simple to use and have the added benefit of working when the vehicle is in a dangerous location such as at the side of a busy highway, or on uneven ground. Flat tire on a Fiat Panda

A water-based sealant can be injected into the tire also through the valve stem. This contains less harmful chemicals and no aerosol gas. The sealant can then be driven into the tire using an air compressor. A flat tire can be repaired by a patch or plug; or the tire may repair itself. Self-sealing tires work on punctures up to a certain size. The patch repair is commonly used in a repair shop. Some may not patch a worn tire if: the hole is close to a previous patch, there are already more than two patches, the puncture requires more than two patches, the punctures are too close, and/or the puncture is close to the sidewall. A patch is performed by removing the tire, marking the puncture, scouring the surface to create a smooth surface (inside of the tire), applying rubber cement, applying the patch, then pressing it into the surface with a small metal wheel attached to a handle. An alternative is a combination patch and plug. This is manufactured with a plug built into it; applying this patch is done similarly except with more steps, including drilling a hole at the puncture so the plug can be pulled through it, as well as cutting off the excess plug from the outside the tire. The final method, the tire plug, can be performed without removing the tire. The penetrating object is removed from the tire, and a plug coated in rubber cement then inserted with a handle, typically supplied with the kit. Many technicians consider plugs less reliable than patching though more reliable than sealant. One disadvantage of patching a tire is that due to the process requiring one to remove the tire from the wheel, the tire must be balanced again when it is put back on the wheel. Tire sealant also creates an imbalance in the tire, but since it is a temporary repair, it is considered less of an issue. However, the issue of disposal of the tire sealant, the hazards to the technician, as well as the required cleaning of both the inside of the tire as well as the wheel could all be considered disadvantages of tire sealant. Tires can leak air for a variety of reasons. These include, but are not limited to: damage to the wheel itself, a damaged valve stem, a puncture in the tire (which can be hard to find if the puncturing object didn't embed itself in the tire) and improper installation of the tire, which could involve the bead of the tire being cut when installed with excessive force. Occasionally, a puncture may not "go all the way through" to the inside of the tire. Thus, before coming to the conclusion that a puncture is causing air to leak from the tire, attempt to remove the puncture lightly by hand. It's very possible that the head of a nail or a very short nail created the appearance of a puncture, while not actually being one. Also worth mentioning is the fact that tires simply lose air over time. A brand new tire, properly inflated, will lose air even with no punctures present. This is mainly due to the design of the valve stem, among other reasons. Given enough time, a tire can fully deflate with no outside intervention.

Bicycles

Thin-walled tires, especially those used in road racing bicycles are particularly susceptible to puncture by road debris, such as thorns, and small pieces of glass that would not affect tires with more substantial tread. The equipment needed to repair or replace a bicycle inner tube is comparatively minimal, and frequently carried by cyclists. On the road, the easiest approach to a flat tire, should a spare inner tube be available, is to replace the tube. The wheel is removed, the tire levered from the rim and inspected for causes of damage, and the inner tube replaced and wheel inflated. Re-inflation can be carried out by the use of a frame mounted pump or a cartridge inflator. The cartridge is generally a single use item only while the pump can be used to inflate many flat tires. The inner tube may then be repaired at a later date. Puncture-repaire-kit

The repair of inner tubes may be necessary on the road. Several methods exist to locate a small puncture, including submersion in water with dish soap, but without a bowl of water available, the simplest method may be to inflate the tube until air can be felt escaping from the puncture. Once located, the puncture is cleaned, and a patch applied (see

Louis Rustin Louis Désiré Auguste Rustin (1880-1954) was a French cyclist and repairer of tyres in Paris who invented the puncture patch.Cyclotourisme, F, December 2011, p53 Car and bicycle tyres had until then been complicated to mend after the inner tube, w ...

for the invention of the puncture patch). Note that tire valves may also become damaged. In this case, repair of the inner tube will not be possible, and the tube should be replaced. Should damage to the tread of the outer tire be substantial, a tough, self-adhesive patch, known as a boot may additionally be placed inside the tire. Folded paper currency is frequently used as a makeshift boot by cyclists in need. Racing bicycles frequently use tubular tires, which are glued to a special, flat wheel rim. The use of these is often restricted to circumstances where a full spare wheel is available. Another approach to preventing punctures of lightweight tires is to use

kevlar Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s a ...

belts in the tire tread construction. Another approach to preventing punctures in bicycle and other tires in general is the use of

Slime Slime may refer to: Biology * Slime mold, a broad term often referring to roughly six groups of Eukaryotes * Biofilm, an aggregate of microorganisms in which cells adhere to each other and/or to a surface * Slimy (fish), also known as the pony ...

, a proprietary brand of injectable liquid thick chemica
''goo''
This chemical "goo" has a tendency to stick to, and coat the outer wall of the inner tube or tire, thus adding another layer of flexible rubber-type protection on the inside of the inner tube or tire. Many MTB riders, or "Mountain Bike Riders", further pre-treat their tires to prevent serious punctures or to prevent punctures in the first place. There are other brands of this same type of liquid, either in an unpressurized container or pressurized container with inflatable gas which is sold in many auto and bicycle stores. The auto sales version of this

Fix-A-Flat Canned tire inflators are single-use devices created by Adam Vazquez as a, temporary solution to drivers who experience flat tires. These devices seal the punctured tire and then reinflate it with pressurized gas, providing enough pressure to allow ...

type of chemical is sold in America.

Dangers of changing a flat tire

Motorists stranded by a flat tire face a number of hazards. The most common hazard is from the passing traffic. Especially if the tire is on the side closer to the road, the motorist is at risk of getting hit by a passing car. If the motorist is unable to pull over to a place where the tire being changed is on the opposite side from the moving traffic, he may be directly in the path of or just inches away from passing cars. Even if some type of warning is placed on the road, a motorist not fully attentive may not be able to avoid the situation. Some motorists, especially those with less physical strength, may risk injury while attempting to change a tire. Often,

lug nut A lug nut or wheel nut is a fastener, specifically a nut, used to secure a wheel on a vehicle. Typically, lug nuts are found on automobiles, trucks (lorries), and other large vehicles using rubber tires. Design A lug nut is a nut fastener wi ...

s are bolted very tightly to the wheel, and tires themselves are quite heavy. While the use of a

run-flat tire A run-flat tire/tyre is a pneumatic vehicle tire that is designed to resist the effects of deflation when punctured, and to allow the vehicle to continue to be driven at reduced speeds - under – and for limited distances – usually , dependin ...