Tire

If a tire wears out of shape, or gets flat-spotted, but has a reasonable amount of metal left, it can be turned on a wheel lathe to refinish it, reshaping it to the correct profile. The incidence of twinning among cattle is about 1-4%, and research is underway to improve the odds of twinning, which can be more profitable for the breeder if complications can be sidestepped or managed. Tires are reasonably thick, up to about an inch thick or more, giving plenty of room to wear. Multiple births are common in many animal species, such as cats, sheep, and ferrets. Removing a tire is done in reverse - the tire is heated while on the wheel until it loosens. In this case, although the twins did come from the same egg, it is incorrect to refer to them as genetically identical, since they have different karyotypes. When cold, friction between the tire and the wheel is such that the tire will not budge even under quite extreme forces. When monozygotic twins are born with different genders it is because of chromosomal birth defects.

After placing it on the wheel, the tire is cooled, and it shrink fits onto the wheel. The probability of this is so vanishingly small (only 3 documented cases) that multiples having different genders is universally accepted as a sound basis for a clinical determination that in utero multiples are not monozygotic. As the tire heats, it expands, making it big enough to fit around the wheel. Among monozygotic twins, in extremely rare cases, twins have been born with opposite sexes (one male, one female). Railroad workshops generally have special equipment to do so. One 1992 study estimates that the frequency of heteropaternal superfecundation among dizygotic twins whose parents were involved in paternity suits was approximately 2.4%; see the references section, below, for more details. To fit a tire, it is heated up until it is glowing hot. This can lead to the possibility of a woman carrying fraternal twins with different fathers (that is, half-siblings).

As with wagon wheels, the tire is held by an interference fit - it is made slightly smaller than the wheel on which it is supposed to fit. Among fraternal twins, in rare cases, the eggs are fertilised at different times with two or more acts of sexual intercourse, either within one menstrual cycle (superfecundation) or, even more rarely, later on in the pregnancy (superfetation). No obvious form of fastening is generally used to attach it. There are some patterns of twinning that are exceedingly rare: while they have been reported to happen, they are so unusual that most obstetricians or midwives may go their entire careers without encountering a single case. The tire is a hoop of steel that is fitted around the steel or iron wheel. Twins that have been separated early in life and raised in separate households are especially sought-after for these studies, which have been invaluable in the exploration of human nature. Replacing a whole wheel because of a worn contact surface proves expensive, so the concept of fitting steel tires to train wheels came about. Twin studies are studies that assess identical (monozygotic) twins for medical, genetic, or psychological characteristics to try to isolate genetic influence from environmental influence.

The friction so caused can heat the wheel (and rail) enough to cause permanent heat damage. Many fertility treatments have no effect on the likelihood of multiple births. Another, different form of damage to a train's wheels takes place if violent wheelslip occurs. Some other treatments such as the drug Clomid can stimulate a woman to release multiple eggs, allowing the possibility of multiples. Wear can also take place unevenly if wheels lock up under heavy braking, causing flat spots. With in vitro fertilisation (IVF), this is primarily due to the insertion of multiple embryos into the uterus. The shape of a train wheel is designed and specified precisely for the best possible riding and cornering characteristics, and too much wear can alter that. This can vary depending on what types of fertility treatments are used.

As well as the simple wearing away of the wheel surface, a wheel that wears begins to deviate from the correct profile. Women undergoing certain fertility treatments may have a greater chance of multiple births. Efficient though the rolling of steel wheel on steel rail is, wear still takes place - on acceleration, on braking, and on cornering. Dizygotic twin pregnancies are slightly more likely when the following factors are present in the woman:. (Some trains, mostly certain types of metros and people movers, have rubber tires, including some lines of the Paris Métro, the Mexico City Metro, the Caracas Metro and the Montreal Metro). Some evidence suggests that the environment of the womb causes the zygote to split in most cases. The steel wheels of trains are fitted with tires which are themselves usually made of steel. Fewer than 20 families have been described with an inherited tendency towards monozygotic twinning (people in these families have nearly a 50% chance of delivering monozygotic twins).

See: Tire manufacturing. The cause of monozygotic twinning is unknown. Because of slow leaks or changes in weather or other conditions, tire pressure may occasionally have to be adjusted, usually by refilling through the valve stem with some pressurized air which is often available at service stations. Multiple pregnancies are usually delivered before the full term of 40 weeks gestation: the average length of pregnancy is around 36 weeks for twins, 34 weeks for triplets and 32 weeks for quadruplets. There are simple hand-held tire-pressure gauges which can be temporarily attached to the valve stem to check a tire's interior air pressure. Before the advent of ovulation-stimulating drugs, triplets were quite rare (approximately 1 in 8000 births) and higher order births so rare as to be almost unheard of. Routine maintenance including tire rotation, exchanging the front and rear tires with each other, is often done periodically to even out tire wear. If there are three, they are called triplets; four, quadruplets; five, quintuplets; six, sextuplets, seven, septuplets, and so on.

Front tires, especially on front wheel drive vehicles, have a tendency to wear out more quickly than rear tires. Sometimes multiple births may involve more than two fetuses. Alternatively, many modern cars and trucks are equipped with run flat tires that may be driven with a puncture - or perhaps are even self-repairing for moderate sized holes. Nevertheless, the rate of identical twins remains at about 1 in 250 across the globe, further suggesting that pregnancies resulting in identical twins occur randomly. Cans of pressurized "gas" can sometimes be bought separately for convenient emergency refill of a tire. Thus, approximately 6% of children born in the US in 2001 were twins. Not included, but sometimes available separately, are hand or foot pumps for filling a tire with air by the vehicle owner. In 2001, for the first time ever in the US, the twinning rate exceeded 3% of all births.

Jacks and tire irons for emergency replacement of a flat tire with a spare tire are included when buying a new car. The widespread use of fertility drugs causing hyperovulation (stimulated release of multiple eggs by the mother) has caused what some call an "epidemic of multiple births". A few modern vehicle models may use conventional spare tires also. The rate of twinning varies greatly among ethnic groups, ranging as high as about 6% for the Yoruba or 10% for a tiny Brazilian village (see [1]). Years ago, full-size or conventional spare tires were used. Historically, about 1 in 80 human births (1.2%) has been the result of a twin pregnancy. These days, most spare tires for cars are smaller than normal tires (to save on trunk space, gas mileage, and cost) and should not be driven very far before replacement with a full-size tire. Similar to vanishing twin.

Vehicles typically carry a spare tire, already mounted on a rim, to be used in case a flat tire or blowout occurs. Occasionally, a woman will suffer a miscarriage early in pregnancy, yet the pregnancy will continue; one twin was miscarried but the other was able to be carried to term. Occasionally, other types of damage require replacement of a tire. A chimera may arise either from identical twin fetuses (where it would be impossible to detect), or from dizygotic fetuses, which could be identified by chromosomal comparisons from various parts of the body. This replacement means the tire will have to be taken off the rim and remounted after the valve replacement. A chimera is a person who is a completely normal human with no extra parts, but some of the parts actually came from his or her twin. A leaking valve stem may occasionally be the cause of a leak, necessitating valve stem replacement. Sometimes the parasitic twin just becomes an almost indistinguishable part of the other.

The damaged tire typically must be replaced after that. One fetus acts as a parasite towards the other. Sometimes a more serious rupture of the tire material occurs resulting in a blowout. Sometimes one twin fetus will fail to develop completely and continue to cause problems for its surviving twin. Tire repair with such patches requires the tire to be taken off the rim and then remounted after the patch is applied. This condition occurs in about 1 in 100,000 pregnancies. Patches covering a hole have been glued or rubber-cemented to the interior surface of a tire also, particularly if a hole is too elongated for a simple plug. This occurs where the single zygote of identical twins fails to separate completely.

The rubber covering the plug solidifies rather quickly, after which the protruding ends of the plug can be cut off, the tire can be refilled with air to the appropriate pressure, and the repaired wheel replaced on the vehicle. Conjoined twins are monozygotic twins, whose bodies are joined together at birth. Then a plug coated with a semi-liquid form of rubber can be inserted into the hole with a special tool. Early obstetric ultrasonography exams sometimes reveal an "extra" fetus, which fails to develop and instead disintegrates and vanishes. A puncturing object, such as a nail or a screw, can be pulled out using pliers. Researchers suspect that more pregnancies start out as multiples than come to term that way. If submerging a tire underwater is not possible, the leak can be searched for by covering the pressurized tire surface with a soapy solution to see where leaking air forms soap bubbles. Such conditions are usually associated with a higher incidence of other birth defects.

A leak in a tire can often be found by submerging the tire, pressurized with air, under water to see where air bubbles come out. This is where some or all of the organs will be on the opposite side of the body, such as the heart being on the right(Dextrocardia). If the hole is small and not elongated, the tire can often be repaired by using plugs from a tire repair kit. One mirror may or may not have situs inversus. Many leaks in flat tires, though, are caused by nails, screws, caltrops, broken glass or other sharp objects puncturing the rubber tire wall. They result from a late split of the fertilized egg at around 9-12 days. A leak may be slow in a few cases, such as is sometimes observed when the seal between the rim and tire edge is not perfect. The incidence of mirror twinning is comparatively rare.

Sometimes a pneumatic tire gets a hole or a leak through which the air inside leaks out resulting in a flat tire, a condition which must be fixed before the car can be driven further safely. These are identical twins with opposite features, that is one may be right handed and the other may be left handed; hair will whorl in the opposite direction, and so on. Because this bonding may occasionally come loose on the tire, new tires are superior to recapped tires. Some percentage of monozygotic twins are called "mirror twins" or mirror image twins. a new layer of rubber with grooves is bonded onto the outer perimeter of a worn tire. (Fraga, et al., 2005). e. Twins who had spent their lives apart (such as those adopted by two different sets of parents at birth) had the greatest difference.

Sometimes tires with worn tread are recapped, i. 50-year-old twins had over 3 times the epigenetic difference that the 3-year-old twins had. A bald tire should be replaced as soon as possible. The number of differences between identical twins increases with age. When the tread is worn away completely and especially when the wear on the outer rubber exposes the reinforcing threads inside them, the tire is said to be bald. A study of 80 pairs of twins ranging in age from 3 to 74 showed that the youngest twins have relatively few epigenetic differences. More wear on a tire facing the outside or the inside of a car is often a sign of bad wheel alignment. This is called epigenetic modification.

Uneven or accelerated tire wear can be caused by bad wheel alignment. Identical twins have identical DNA but differing environmental influences throughout their lives affect which genes are switched on or off. The same tire rims can usually be used throughout the lifetime of the car. There are usually obvious signs of differences when the identical twins are observed separately or together. When the tire tread becomes too shallow, the tire is worn out and should be replaced. Twins are unique individuals that establish their own individual likes and dislikes. Friction from moving contact with the road causes the tread on the outer perimeter of the tire to eventually wear away. Many identical twins spend most of their time together (especially as children), so people often assume that they will behave alike just as they look alike; however, this is not the case.

This is likely to increase the tire life, but may turn out to be a bad idea if the worn out part of nanocarbon deposited on the roads is washed off and ends up in the food chain. They develop their own individual personalities to enable themselves to be identified as individual persons. There is currently an attempt to reinforce the tire with nanomaterial. Identical twins can behave as differently as any other siblings (a matter of much interest to psychologists). Essentially, part of the tire tread is shallower than the rest and will show when the tire is worn down to that level. The exact cause for the splitting of a zygote or embryo is unknown. Wearbars may be designed into the tire tread to indicate when it is time to replace the tire. While it was originally thought that identical twins do not run in families, but occur more or less randomly, some recent research has suggested that a genetic predisposition may exist.

Local legislation may specify minimum tread depths, typically between 1/8" (3.2 mm) and 1/32" (0.8 mm). As they mature, identical twins often become less alike because of lifestyle choices or external influences such as scars. Tire tread gauges are small rulers designed to be inserted into tire treads to measure the remaining tread depth. Examination of details such as fingerprints can tell them apart. Tire rotation moves tires between the different wheels of the vehicle as front and back axles carry different loads and thus the tires wear differently. (On extremely rare occasions, an original XXY zygote may form monozygotic boy/girl twins by dropping the Y chromosome for one twin and the extra X chromosome for the other.) Monozygotic twins generally look alike, although sometimes they appear as mirror images of each other. It is important not to put a 'clockwise' tire on the left hand side of the car or a 'counter-clockwise' tire on the right side. Monozygotic twins are genetically identical unless there has been a mutation in development, and they are almost always the same gender.

Some tread designs are unidirectional and the tire has a rotation direction indicated by an arrow showing which way the tire should rotate when the vehicle is moving forwards. About 50% of mono-mono twins die from umbilical cord entanglement. New automotive tires now also have ratings for traction, treadwear, and temperature resistance (collectively known as UTQG ratings); as well as speed and load ratings. These twins may develop such that blood passes disproportionately from one twin to the other through connecting blood vessels within their shared placenta, leading to twin-to-twin transfusion syndrome. See tire code. Monochorionic twins, sharing one placenta, usually also share the placental blood supply. Automobile tires have numerous rating systems. For example, the umbilical cords of monoamniotic twins can become entangled, reducing or interrupting the blood supply to the developing fetus.

This is known in general throughout the industry as Tyre Uniformity. Sharing the same amnion (or the same amnion and placenta) can cause complications in pregnancy. Tires outside the specified limits for RFV and LFV are rejected. Twinning after 12 days post-fertilization will typically result in conjoined twins. These variations are measured as Radial Force Variation and Lateral Force Variation, which are measured on a Force Variation Machine at the end of the manufaturing process. Twinning between 8 to 12 days after fertilization will usually result in monochorionic-monoamniotic ("mono-mono") twins. This was because the structure and manufacture of a radial tire lends itself to the problems of variation in stiffnes around the tyre. Twinning between 4 to 8 days after fertilization typically results in monochorionic-diamniotic ("mono-di") twins.

With the introduction of radial tires, however, it was found that some vibrations could not be cured by adding balance weights. Zygotes that twin at the earliest stages will be diamniotic and dichorionic ("di-di"). Such tire balancing with these kind of weights avoids vibration when the vehicle is driven at higher speeds. The later in pregnancy that twinning occurs, the more structures will be shared. Because tires are often not made with perfectly even mass all around the tire, a special tire-balancing apparatus at a repair shop spins the wheel with the tire to determine where small weights should be attached to the outer edge of the rim to balance out the wheel. This condition does not occur for fraternal twins. The rim with the tire mounted onto it comprises the removable wheel, which is then attached to the vehicle through a number of holes in the rim using lug nuts. Also note that any monochorionic or monoamniotic twins are identical twins.

After mounting, the tire is inflated (pressurized) with air through the valve stem to manufacturer's specified pressure, which is more than atmospheric pressure. All monoamniotic twins are monochorionic. The common motor vehicle tire is mounted around a steel rim at service stations or repair shops for vehicles using a special tire mounting apparatus while the wheel is off the vehicle. Diamniotic identical twins may share the same placenta (known as monochorionic) or not (dichorionic). The "steering feel" of such tires is also different from that of pneumatic tires, as their solidity does not allow the amount of torsion that exists in the carcass of a pneumatic tire under steering forces, and the resultant sensory feedback through the steering apparatus. Depending on the stage at which the zygote divides, identical twins may share the same amnion (in which case they are known as monoamniotic) or not (diamniotic). The result is a tire which is less forgiving, particularly with regards to sharp transient bumps and provides poor ride and handling characteristics. The two embryos develop into fetuses sharing the same womb.

As a result compression is localised within the tire and the effective spring rate rises sharply as the tire compresses. Identical twins occur when a single egg is fertilized to form one zygote (monozygotic) but the zygote then divides into two separate embryos. "Airless" tires usually employ a type of foam or sponge like construction which consists of a large number of small air filled cells. However, it is only the female that has any influence on the chances of having fraternal twins as the male cannot make her release more than one ovum. The air in conventional pneumatic tires acts as a near constant rate spring because the decrease in the tire's volume as the tire compresses over a bump is minimal. Studies show that there is a genetic basis for fraternal twinning—that is, non-identical twins do run in families. Attempts have been made to make various types of solid tire but none has so far met with much success. Dizygotic twins may be a different sex or the same sex, just as with any other siblings.

Tires are inflated through a Schrader valve. Dizygotic twins, like any siblings, have a very small chance of having the exact same chromosome profile, but most likely have a number of different chromosomes that distinguish them. The air compresses as the wheel goes over a bump and acts as a shock absorber. The two eggs form two zygotes, and these twins are therefore also known as dizygotic as well as "biovular" twins. Pneumatic tires are made of a flexible elastomer material such as rubber with reinforcing threads/wires inside the elastomer material. Fraternal twins (commonly known as "non-identical twins") usually occur when two fertilized eggs are implanted in the uterine wall at the same time. Air-filled tires are known as pneumatic tires, and these are the type in almost universal use today. .

This work was done by a wheelwright, a craftsman who specialized in making wagon wheels. Since some premature births often have health consequence to the babies, twins birth are often handled with special procedures. The tire was heated in a forge, placed on the wheel and quenched, causing the metal to shrink, which drew the rim against the spokes and provided stiffness to the wheel. Due to the limited size of the mother's womb, multiple pregnancy is much less likely to carry to full term than singleton birth (twins usually around 34 to 36 weeks). The earliest tires were hoops of metal placed around wagon wheels. A fetus alone in the womb is called a singleton. Tires with radial yarns (known as radial tires) are standard for almost all modern automobiles. The term twin most notably refers to two individuals (or one of two individuals) who have shared the same uterus (womb) and are usually, but not necessarily, born on the same day.

Pneumatic tires generally have reinforcing threads in them; based on the orientation of the threads, they are classified as bias-ply/cross ply or radial. Several previous pregnancies. The inner tubes are usually made of halobutyl rubber, because of its suitable mechanical properties and excellent impermeability for air. Greater than average height and weight. This method, however, tends to fail desperately if the vehicle is used on rough roads (for example Kenyan roads) as a small bend on the rim (metal wheel) will result in deflation. Between the age of 30 and 40 years. Others, including modern radial tires, use a seal between the metal wheel and the tire to maintain the internal air pressure (tubeless tire). She is of African descent.

This is a fully sealed rubber tube with a valve to control flow of air in and out. Some air-filled tires, especially those used with spoked wheels such as on bicycles, or on vehicles travelling on rough roads, have an inner tube; this was also formerly the case of automobile tires. To avoid tearing at these inner edges, particularly when the tire is being mounted, there are a number of concentric steel wires buried inside the rubber at both inner edges of the tire. The sidewalls are the sections of the tire which are between the crown and the inner circular edges of the tire contacting the rim.

When the tread on the outer perimeter of the tire inevitably wears away from use, reducing the tread depth, the tire should be replaced. The depth of these grooves essentially constitutes the tread depth at any time during the lifetime of the car. Traction is especially important for good braking. Without such grooves, a layer or film of water would form between the wet roads and the tire surface, which would cause hydroplaning, substantially reducing traction.

The water from the rain would be compressed into the grooves by the vehicle's weight, providing better traction in the tire to road contact. These grooves are especially useful during weather with rain (or snow). The outer perimeter of the tire, often called the crown, has various designs of jagged shaped grooves in it. Fowler also notes that the altered spelling tyre originally met with resistance from conservative British institutions such as The Times newspaper.

According to the Oxford English Dictionary, quoted in Fowler's Modern English Usage, the word is a shortening of attire, and the British spelling tyre is a recent divergence from historical tradition. External link: Robert William Thomson. In 2005, Michelin was reported to be attempting to develop a tire and wheel combination, the Tweel, which does not use air. All modern car tires are now radial.

This type of tire uses parallel carcass plies for the sidewalls and crossed belts for the crown of the tire. The radial tire was invented by Michelin, a French company, in 1946, but did not see wide use in the United States, the largest market at that time, until the 1970s. Dunlop's company has since merged with the Bridgestone company, after a brief partnership with Pirelli. The invention quickly caught on for bicycles and was later adapted for use on cars.

Dunlop partnered with William Harvey du Cros to form a company which later became the Dunlop Rubber Company to produce his invention. By Dunlop's time, the bicycle had been fully developed (see Rover) and it proved a far more suitable application for pneumatic tires. Because neither bicycles nor automobiles had been invented when Thomson produced his tire, that tire was only applied to horse drawn carriages. It wasn't long before rubber inner tubes were invented.

Dunlop's tire had a modified leather hosepipe as an inner tube and rubber treads. John Dunlop re-invented the tire for his ten year old son's tricycle in 1887 and was awarded a patent for his tire in 1888 (rescinded 1890). The tire gave a good ride, but there were so many manufacturing and fitting problems that the idea had to be abandoned. This invention consisted of a canvas inner tube surrounded by a leather outer tire.

In 1845 the first pneumatic (inflatable) tire was patented by fellow Scotsman, the engineer Robert William Thomson as the Aerial Wheel. John Boyd Dunlop, a Scottish veterinary surgeon working in Belfast, Ireland, is widely recognized as the father of the modern tire, although he was not the first to come up with the idea. In 1844, Charles Goodyear invented vulcanization, the process that would later be used to produce cured rubber tires. The modern tire came about in stages in the 19th century.

For most of history wheels had very little in the way of shock absorption and journeys were very bumpy and uncomfortable. .
. spelling) or tyre (UK spelling) is a roughly toroidal piece of material placed on the circumference of a wheel, either for the purpose of cushioning or to protect the wheel from wear and tear.

A tire (U.S. The large lugs on mud tires tend to tear and chip on roads, because they are made from hard rubber compounds that do not bend easily. They can be noisy at highway speeds, and due to the open tread design, they have less of a contact area with the road, limiting traction. Depending on the composition and tread pattern, many mud terrain tires are not well suited to on-road use.

Mud terrain tires also tend to be wider than other tires, to spread the weight of the vehicle over a greater contact patch to prevent the vehicle from sinking too deep into the mud. The large open design also allows mud to clear more quickly from between the lugs. Mud terrain tires are characterized by large, chunky tread patterns designed to bite into muddy surfaces and provide grip. Mud tires