AUTOMOBILE REPAIR SHOPS

An automobile repair shop (also known as a garage) is a place where automobiles are repaired by auto mechanics and electricians.

Types

A Midas repair shop in Durham, North Carolina.

Some auto parts stores also maintain service operations. Examples include Pep Boys, Walmart, and Sears Auto Center.

There are also independently owned and operated businesses like Suchorski's Auto Repair in Milwaukee, WI or regional or national chains and franchises. Examples of chains and franchises include Midas and Firestone Complete Auto Care.

A third type of repair shop is the service departments of car dealerships. These shops are the only ones authorized to perform warranty and recall repairs by the manufacturers and distributors, excepting in the European Union.

Specialty

A shop specializing in mufflers, brakes, and shocks in Durham, North Carolina.

Automobile repair shops can be specialty shops like muffler shops, transmission specialists, body shop, tire shops and automobile electrification shops. Examples include MAACO and AAMCO. There are also independently-owned specialists who work only on specific makes of cars, such as European car specialists and BMW repair specialists.

Green Garages

Green garages are dedicated to electric vehicles.

WHAT IS A LUBE, OR LUBRICANT

A lubricant (sometimes referred to as "lube") is a substance (often a liquid) introduced between two moving surfaces to reduce the friction between them, improving efficiency and reducing wear. They may also have the function of dissolving or transporting foreign particles and of distributing heat.

One of the single largest applications for lubricants, in the form of motor oil, is to protect the internal combustion engines in motor vehicles and powered equipment.

Typically lubricants contain 90% base oil (most often petroleum fractions, called mineral oils) and less than 10% additives. Vegetable oils or synthetic liquids such as hydrogenated polyolefins, esters, silicone, fluorocarbons and many others are sometimes used as base oils. Additives deliver reduced friction and wear, increased viscosity, improved viscosity index, resistance to corrosion and oxidation, aging or contamination, etc.

Lubricants such as 2-cycle oil are also added to some fuels. Sulfur impurities in fuels also provide some lubrication properties, which has to be taken in account when switching to a low-sulfur diesel; biodiesel is a popular diesel fuel additive providing additional lubricity.

Non-liquid lubricants include grease, powders (dry graphite, PTFE, Molybdenum disulfide, tungsten disulfide, etc.), Teflon tape used in plumbing, air cushion and others. Dry lubricants such as graphite, molybdenum disulfide and tungsten disulfide also offer lubrication at temperatures (up to 350 °C) higher than liquid and oil-based lubricants are able to operate. Limited interest has been shown in low friction properties of compacted oxide glaze layers formed at several hundred degrees Celsius in metallic sliding systems, however, practical use is still many years away due to their physically unstable nature.

Another approach to reducing friction and wear is to use bearings such as ball bearings, roller bearings or air bearings, which in turn require internal lubrication themselves, or to use sound, in the case of acoustic lubrication.

In addition to industrial applications, lubricants are used for many other purposes. Other uses include biomedical applications (e.g. lubricants for artificial joints) and the use of personal lubricant for sexual purposes.

Purpose

Lubricants perform the following key functions.

• Keep moving parts apart
• Reduce friction
• Transfer heat
• Carry away contaminants & debris
• Transmit power
• Protect against wear
• Prevent corrosion
• Seal for gasses
• Stop the risk of smoke and fire of objects

Keep moving parts apart

Lubricants are typically used to separate moving parts in a system. This has the benefit of reducing friction and surface fatigue together with reduced heat generation, operating noise and vibrations. Lubricants achieve this by several ways. The most common is by forming a physical barrier i.e. a thin layer of lubricant separates the moving parts. This is termed hydrodynamic lubrication. In cases of high surface pressures or temperatures the fluid film is much thinner and some of the forces are transmitted between the surfaces through the lubricant. This is termed elasto-hydrodynamic lubrication.

Reduce friction

Typically the lubricant-to-surface friction is much less than surface-to-surface friction in a system without any lubrication. Thus use of a lubricant reduces the overall system friction. Reduced friction has the benefit of reducing heat generation and reduced formation of wear particles as well as improved efficiency. Lubricants may contain additives known as friction modifiers that chemically bind to metal surfaces to reduce surface friction even when there is insufficient bulk lubricant present for hydrodynamic lubrication, e.g. protecting the valve train in a car engine at startup.

Transfer heat

Both gas and liquid lubricants can transfer heat. However, liquid lubricants are much more effective on account of their high specific heat capacity. Typically the liquid lubricant is constantly circulated to and from a cooler part of the system, although lubricants may be used to warm as well as to cool when a regulated temperature is required. This circulating flow also determines the amount of heat that is carried away in any given unit of time. High flow systems can carry away a lot of heat and have the additional benefit of reducing the thermal stress on the lubricant. Thus lower cost liquid lubricants may be used. The primary drawback is that high flows typically require larger sumps and bigger cooling units. A secondary drawback is that a high flow system that relies on the flow rate to protect the lubricant from thermal stress is susceptible to catastrophic failure during sudden system shut downs. An automotive oil-cooled turbocharger is a typical example. Turbochargers get red hot during operation and the oil that is cooling them only survives as its residence time in the system is very short i.e. high flow rate. If the system is shut down suddenly (pulling into a service area after a high speed drive and stopping the engine) the oil that is in the turbo charger immediately oxidizes and will clog the oil ways with deposits. Over time these deposits can completely block the oil ways, reducing the cooling with the result that the turbo charger experiences total failure typically with seized bearings. Non-flowing lubricants such as greases & pastes are not effective at heat transfer although they do contribute by reducing the generation of heat in the first place.

Carry away contaminants and debris

Lubricant circulation systems have the benefit of carrying away internally generated debris and external contaminants that get introduced into the system to a filter where they can be removed. Lubricants for machines that regularly generate debris or contaminants such as automotive engines typically contain detergent and dispersant additives to assist in debris and contaminant transport to the filter and removal. Over time the filter will get clogged and require cleaning or replacement, hence the recommendation to change a car's oil filter at the same time as changing the oil. In closed systems such as gear boxes the filter may be supplemented by a magnet to attract any iron fines that get created.

It is apparent that in a circulatory system the oil will only be as clean as the filter can make it, thus it is unfortunate that there are no industry standards by which consumers can readily assess the filtering ability of various automotive filters. Poor filtration significantly reduces the life of the machine (engine) as well as making the system inefficient.

Transmit power

Pascal's law is at the heart of hydrostatic power transmission. Hydraulic fluids comprise a large portion of all lubricants produced in the world.

Protect against wear

Lubricants prevent wear by keeping the moving parts apart. Lubricants may also contain anti-wear or extreme pressure additives to boost their performance against wear and fatigue.

Prevent corrosion

Good quality lubricants are typically formulated with additives that form chemical bonds with surfaces to prevent corrosion and rust.

Seal for gasses

Lubricants will occupy the clearance between moving parts through the capillary force, thus sealing the clearance. This effect can be used to seal pistons and shafts.

History

Romans used rags dipped in animal fat to lubricate wagon wheels; however the science of lubrication (tribology) really only took off with the industrial revolution in the nineteenth century.

General composition

Lubricants are generally composed of a majority of base oil and a minority of additives to impart desirable characteristics.

Types of lubricants

• Liquid including emulsions and suspensions
• Solid
• Greases
• Adhesive

Liquid lubricants

Liquid lubricants may be characterized in many different ways. One of the most common ways is by the type of base oil used. Following are the most common types.

• Lanolin (wool grease, natural water repellent)
• Water
• Mineral oils
• Vegetable (natural oil)
• Synthetic oils
• Others

Note: although generally lubricants are based on one type of base oil or another, it is quite possible to use mixtures of the base oils to meet performance requirements.

Lanolin

A natural water repellent, lanolin is derived from sheep wool grease, and is an alternative to the more common petrochemical based lubricants. This lubricant is also a corrosion inhibitor, protecting against rust, salts, and acids.

Water

Water can be used on its own, or as a major component in combination with one of the other base oils. Commonly used in engineering processes, such as milling and lathe turning.

Mineral oil

This term is used to encompass lubricating base oil derived from crude oil. The American Petroleum Institute (API) designates several types of lubricant base oil identified as:

• Group I - Saturates <90% and/or sulfur >0.03%, and Society of Automotive Engineers (SAE) viscosity index (VI) = >80 to <120

- Manufactured by solvent extraction, solvent or catalytic dewaxing, and hydro-finishing processes. Common Group I base oil are 150SN (solvent neutral), 500SN, and 150BS (brightstok)

• Group II – Saturates >90% and sulfur <0.03%, and SAE viscosity index >80 to <120

- Manufactured by hydrocracking and solvent or catalytic dewaxing processes. Group II base oil has superior anti-oxidation properties since virtually all hydrocarbon molecules are saturated. It has water-white color.

• Group III – Saturates > 90%, sulfur <0.03%, and SAE viscosity index >120

- Manufactured by special processes such as isohydromerization. Can be manufactured from base oil or slax wax from dewaxing process.

• Group IV – Polyalphaolefins (PAO)
• Group V – All others not included above

Such as naphthenics, PAG, esters, and etc.

In North America, Groups III, IV and V are now described as synthetic lubricants, with group III frequently described as synthesized hydrocarbons, or SHCs. In Europe, only Groups IV and V may be classed as synthetics.

The lubricant industry commonly extends this group terminology to include:

• Group I+ with a Viscosity Index of 103 - 108
• Group II+ with a Viscosity Index of 113 - 119
• Group III+ with a Viscosity Index of >= 140

Can also be classified into three categories depending on the prevailing compositions: - Paraffinic - Naphthenic - Aromatic

While lubricants for use in internal combustion engines may solely consist of one of the above-mentioned oil groups, it is not desirable in practice. Additives to reduce oxidation, improve lubrication are added to the final product. The main constituent of such lubricant product is called the base oil, base stock. While it is advantageous to have a high-grade base oil in a lubricant, proper selection of the lubricant additives is equally as important. Thus some poorly selected formulation of PAO lubricant may not last as long as more expensive formulation of Group III+ lubricant.

Vegetable (natural) oils

These are primarily triglyceride esters derived from plants and animals. For lubricant base oil use the vegetable derived materials are preferred. Common ones include high oleic canola oil, castor oil, palm oil, sunflower seed oil and rapeseed oil from vegetable, and Tall oil from animal sources. Many vegetable oils are often hydrolyzed to yield the acids which are subsequently combined selectively to form specialist synthetic esters.

Synthetic oils

• Polyalpha-olefin (PAO)
• Synthetic esters
• Polyalkylene glycols (PAG)
• Phosphate esters
• Alkylated naphthalenes (AN)
• Silicate esters
• Ionic fluids

Solid lubricants

Teflon or PTFE

Teflon or PTFE is typically used as a coating layer on, for example, cooking utensils to provide a nonstick surface. Its usable temperature range up to 350°C and chemical inertness make it a useful additive in special greases. Under extreme pressures, Teflon powder or solids is of little value as it is soft and flows away from the area of contact. Ceramic or metal or alloy lubricants must be used then.

Mineral

Graphite, hexagonal Boron nitride, Molybdenum disulfide and Tungsten disulfide are examples of materials that can be used as solid lubricants, often to very high temperature. The use of some such materials is sometimes restricted by their poor resistance to oxidation (e.g., molybdenum disulfide can only be used up to 350°C in air, but 1100°C in reducing environments).

Metal/alloy

Metal alloys, composites and pure metals can be used as grease additives or the sole constituents of sliding surfaces and bearings. Cadmium and Gold are used for plating surfaces which gives them good corrosion resistance and sliding properties, Lead, Tin, Zinc alloys and various Bronze alloys are used as sliding bearings, or their powder can be used to lubricate sliding surfaces alone, or as additives to greases.

Other relevant phenomena

'Glaze' formation (high temperature wear)

A further phenomenon that has undergone investigation in relation to high temperature wear prevention and lubrication, is that of 'glaze' formation. This is the generation of a compacted oxide layer which sinters together to form a crystalline 'glaze' (not the amorphous layer seen in pottery) generally at high temperatures, from metallic surfaces sliding against each other (or a metallic surface against a ceramic surface). Due to the elimination of metallic contact and adhesion by the generation of oxide, friction and wear is reduced. Effectively, such a surface is self-lubricating.

As the 'glaze' is already an oxide, it can survive to very high temperatures in air or oxidizing environments. However, it is disadvantaged by it being necessary for the base metal (or ceramic) having to undergo some wear first to generate sufficient oxide debris.

Additives

A large number of additives are used to impart performance characteristics to the lubricants. The main families of additives are:

• Antioxidants
• Detergents
• Anti-wear
• Metal deactivators
• Corrosion inhibitors, Rust inhibitors
• Friction modifiers
• Extreme Pressure
• Anti-foaming agents
• Viscosity index improvers
• Demulsifying/Emulsifying
• Stickiness improver, provide adhesive property towards tool surface (in metalworking)
• Complexing agent (in case of greases)

Note that many of the basic chemical compounds used as detergents (example: calcium sulfonate) serve the purpose of the first seven items in the list as well. Usually it is not economically or technically feasible to use a single do-it-all additive compound. Oils for hypoid gear lubrication will contain high content of EP additives. Grease lubricants may contain large amount of solid particle friction modifiers, such as graphite, molybden sulfide, etc.

Application by fluid types

• Automotive
  • Engine oils
    • Petrol (Gasoline) engine oils
    • Diesel engine oils
  • Automatic transmission fluid
  • Gearbox fluids
  • Brake fluids
  • Hydraulic fluids
• Tractor (one lubricant for all systems)
  • Universal Tractor Transmission Oil - UTTO
  • Super Tractor Oil Universal - STOU - includes engine
• Other motors
  • 2-stroke engine oils
• Industrial
  • Hydraulic oils
  • Air compressor oils
  • Gas Compressor oils
  • Gear oils
  • Bearing and circulating system oils
  • Refrigerator compressor oils
  • Steam and gas turbine oils
• Aviation
  • Gas turbine engine oils
  • Piston engine oils
• Marine
  • Crosshead cylinder oils
  • Crosshead Crankcase oils
  • Trunk piston engine oils
  • Stern tube lubricants

Marketing

The global lubricant market is generally competitive with numerous manufacturers and marketers. Overall the western market may be considered mature with a flat to declining overall volumes while there is strong growth in the emerging economies. The lubricant marketers generally--- pursue one or more of the following strategies when pursuing business.

• Specification:

The lubricant is said to meet a certain specification. In the consumer market, this is often supported by a logo, symbol or words that inform the consumer that the lubricant marketer has obtained independent verification of conformance to the specification. Examples of these include the API’s donut logo or the NSF tick mark. The most widely perceived is SAE viscosity specification, like SAE 10W-40. Lubricity specifications are institute and manufacturer based. In the US institute: API S for petrol engines, API C for diesel engines. For 2007 the current specs are API SM and API CJ. Higher second letter marks better oil properties, like lower engine wear supported by tests. In EU the ACEA specifications are used. There are classes A,B,C,E with number following the letter. Japan introduced the JASO specification for motorbike engines. In the industrial market place the specification may take the form of a legal contract to supply a conforming fluid or purchasers may choose to buy on the basis of a manufacturers own published specification.

• Original equipment manufacturer (OEM) approval:

Specifications often denote a minimum acceptable performance levels. Thus many equipment manufacturers add on their own particular requirements or tighten the tolerance on a general specification to meet their particular needs (or doing a different set of tests or using different/own testbed engine). This gives the lubricant marketer an avenue to differentiate their product by designing it to meet an OEM specification. Often, the OEM carries out extensive testing and maintains an active list of approved products. This is a powerful marketing tool in the lubricant marketplace. Text on the back of the motor oil label usually has a list of conformity to some OEM specifications, such as MB, MAN, Volvo, Cummins, VW, BMW or others. Manufactures may have vastly different specifications for the range of engines they make; one may not be completely suitable for some other.

• Performance:

The lubricant marketer claims benefits for the customer based on the superior performance of the lubricant. Such marketing is supported by glamorous advertising, sponsorships of typically sporting events and endorsements. Unfortunately broad performance claims are common in the consumer marketplace, which are difficult or impossible for a typical consumer to verify. In the B2B market place the marketer is normally expected to show data that supports the claims, hence reducing the use of broad claims. Increasing performance, reducing wear and fuel consumption is also aim of the later API, ACEA and car manufacturer oil specifications, so lubricant marketers can back their claims by doing extensive (and expensive) testing.

• Longevity:

The marketer claims that their lubricant maintains its performance over a longer period of time. For example in the consumer market, a typical motor oil change interval is around the 3000-6000 miles (7500-15000 km). The lubricant marketer may offer a lubricant that lasts for 12000 (30000km) miles or more to convince a user to pay a premium. Typically, the consumer would need to check or balance the longer life and any warranties offered by the lubricant manufacturer with the possible loss of equipment manufacturer warranties by not following its schedule. Many car and engine manufacturers support extended drain intervals, but request extended drain interval certified oil used in that case; and sometimes a special oil filter. Example: In older Mercedes-Benz engines and in truck engines one can use engine oil MB 228.1 for basic drain interval. Engine oils conforming with higher specification MB 228.3 may be used twice as long, oil of MB 228.5 specification 3x longer. Note that the oil drain interval is valid for new engine with fuel conforming car manufacturer specification. When using lower grade fuel, or worn engine the oil change interval has to shorten accordingly. In general oils approved for extended use are of higher specification and reduce wear. In the industrial market place the longevity is generally measured in time units and the lubricant marketer can suffer large financial penalties if their claims are not substantiated.

• Efficiency:

The lubricant marketer claims improved equipment efficiency when compared to rival products or technologies, the claim is usually valid when comparing lubricant of higher specification with previous grade. Typically the efficiency is proved by showing a reduction in energy costs to operate the system. Guaranteeing improved efficiency is the goal of some oil test specifications such as API CI-4 Plus for diesel engines. Some car/engine manufacturers also specifically request certain higher efficiency level for lubricants for extended drain intervals.

• Operational tolerance:

The lubricant is claimed to cope with specific operational environment needs. Some common environments include dry, wet, cold, hot, fire risk, high load, high or low speed, chemical compatibility, atmospheric compatibility, pressure or vacuum and various combinations. The usual thermal characteristics is outlined with SAE viscosity given for 100°C, like SAE 30, SAE 40. For low temperature viscosity the SAE xxW mark is used. Both markings can be combined together to form a SAE 0W-60 for example. Viscosity index (VI) marks viscosity change with temperature, with higher VI numbers being more temperature stable.

• Economy:

The marketer offers a lubricant at a lower cost than rivals either in the same grade or a similar one that will fill the purpose for lesser price. (Stationary installations with short drain intervals.) Alternative may be offering a more expensive lubricant and promise return in lower wear, specific fuel consumption or longer drain intervals. (Expensive machinery, unaffordable downtimes.)

• Environment friendly:

The lubricant is said to be environmentally friendly. Typically this is supported by qualifying statements or conformance to generally accepted approvals. Several organizations, typically government sponsored, exist globally to qualify and approve such lubricants by evaluating their potential for environmental harm. Typically, the lubricant manufacturer is allowed to indicate such approval by showing some special mark. Examples include the German “Blue Angel”, European “Daisy” Eco label, Global Eco-Label “GEN mark”, Nordic, “White Swan”, Japanese “Earth friendly mark”; USA “Green Seal”, Canadian “Environmental Choice”, Chinese “Huan”, Singapore “Green Label” and the French “NF Environment mark”.

• Composition:

The marketer claims novel composition of the lubricant which improves some tangible performance over its rivals. Typically the technology is protected via formal patents or other intellectual property protection mechanism to prevent rivals from copying. Lot of claims in this area are simple marketing buzzwords, since most of them are related to a manufacturer specific process naming (which achieves similar results than other ones) but the competition is prohibited from using a trademark.

• Quality:

The marketer claims broad superior quality of its lubricant with no factual evidence. The quality is “proven” by references to famous brand, sporting figure, racing team, some professional endorsement or some similar subjective claim. All motor oil labels wear mark similar to "of outstanding quality" or "quality additives," the actual comparative evidence is always lacking.

Disposal and environmental issues

It is estimated that 40% of all lubricants are released into the environment. Disposal: Recycling, burning, landfill and discharge into water may achieve disposal of used lubricant. There are typically strict regulations in most countries regarding disposal in landfill and discharge into water as even small amount of lubricant can contaminate a large amount of water. Most regulations permit a threshold level of lubricant that may be present in waste streams and companies spend hundreds of millions of dollars annually in treating their waste waters to get to acceptable levels. Burning the lubricant as fuel, typically to generate electricity, is also governed by regulations mainly on account of the relatively high level of additives present. Burning generates both airborne pollutants and ash rich in toxic materials, mainly heavy metal compounds. Thus lubricant burning takes place in specialized facilities that have incorporated special scrubbers to remove airborne pollutants and have access to landfill sites with permits to handle the toxic ash. Unfortunately, most lubricant that ends up directly in the environment is due to general public discharging it onto the ground, into drains and directly into landfills as trash. Other direct contamination sources include runoff from roadways, accidental spillages, natural or man-made disasters and pipeline leakages. Improvement in filtration technologies and processes has now made recycling a viable option (with rising price of base stock and crude oil). Typically various filtration systems remove particulates, additives and oxidation products and recover the base oil. The oil may get refined during the process. This base oil is then treated much the same as virgin base oil however there is considerable reluctance to use recycled oils as they are generally considered inferior. Basestock fractionally vacuum distilled from used lubricants has superior properties to all natural oils, but cost effectiveness depends on many factors. Used lubricant may also be used as refinery feedstock to become part of crude oil. Again there is considerable reluctance to this use as the additives, soot and wear metals will seriously poison/deactivate the critical catalysts in the process. Cost prohibits carrying out both filtration (soot, additives removal) and re-refining (distilling, isomerisation, hydrocrack, etc.) however the primary hindrance to recycling still remains the collection of fluids as refineries need continuous supply in amounts measured in cisterns, rail tanks. Occasionally, unused lubricant requires disposal. The best course of action in such situations is to return it to the manufacturer where it can be processed as a part of fresh batches. Environment: Lubricants both fresh and used can cause considerable damage to the environment mainly due to their high potential of serious water pollution. Further the additives typically contained in lubricant can be toxic to flora and fauna. In used fluids the oxidation products can be toxic as well. Lubricant persistence in the environment largely depends upon the base fluid, however if very toxic additives are used they may negatively affect the persistence. Lanolin lubricants are nontoxic making them the environmental alternative which is safe for both users and the environment.

Societies and industry bodies

API

American Petroleum Institute

STLE

Society of Tribologists and Lubrication Engineers

NLGI

National Lubricating Grease institute

SAE

Society of Automotive Engineers

ILMA

Independent lubricant manufacturer association

European Automobile Manufacturers Association

ACEA

Japanese Automotive Standards Organization

JASO

Major publications

• Peer reviewed
  • Tribology Transactions
  • Journal of Synthetic Lubricants
• Trade periodicals
  • Tribology and Lubrication Technology
  • Fuels & Lubes International
  • Oiltrends
  • Lubes n’ Greases
  • Compoundings
  • Chemical Market Review
  • Machinery lubrication

ABOUT TIRES

Pneumatic automobile tire

An automobile tire failure showing a steel ply

Tires, or tyres (in American and British English, respectively), are ring-shaped parts, either pneumatic or solid (including rubber, metals and plastic composites), that fit around wheels to protect them and enhance their function.

Pneumatic tires are used on many types of vehicles, such as bicycles, motorcycles, cars, trucks, earthmovers, and aircraft. Tires enable better vehicle performance by providing traction and load support. Tires form a flexible cushion between the vehicle and the road, which smoothes out shock and makes for a more comfortable ride while keeping the wheel in more constant contact with the road.

History

The earliest tires were bands of iron (later steel), placed on wooden wheels, used on carts and wagons. The tire would be heated in a forge fire, placed over the wheel and quenched, causing the metal to contract and fit tightly on the wheel. A skilled worker, known as a wheelwright, carried out this work. The outer ring served to "attire" the wheel for use, providing a wear-resistant surface to the perimeter of the wheel. The word "tire" thus emerged as a variant spelling to refer to the metal bands used to dress wheels.

Tire is an older spelling than tyre, but both were used in the 15th and 16th centuries for a metal tire; tire became the settled spelling in the 17th century. In the UK, tyre was revived in the 19th century for pneumatic tyres, possibly because it was used in some patent documents, though many continued to use tire for the iron variety. The Times newspaper was still using tire as late as 1905.

The first practical pneumatic tire was made by the Scot, John Boyd Dunlop, in 1887 for his son's bicycle, in an effort to prevent the headaches his son had while riding on rough roads (Dunlop's patent was later declared invalid because of prior art by fellow Scot Robert William Thomson).

Pneumatic tires are made of a flexible elastomer material, such as rubber, with reinforcing materials such as fabric and wire. Tire companies were first started in the early 20th century, and grew in tandem with the auto industry. Today, over 1 billion tires are produced annually, in over 400 tire factories, with the three top tire makers commanding a 60% global market share.

Chronology

• 1843 – Charles Goodyear announces vulcanization
• 1846 – Robert William Thomson invented and patented the pneumatic tire
• 1888 – First commercial pneumatic bicycle tire produced by Dunlop
• 1889 – John Boyd Dunlop patented the pneumatic tire in the UK
• 1890 – Dunlop, and William Harvey Du Cros began production of pneumatic tires in Ireland
• 1890 – Bartlett Clincher rim introduced
• 1891 – Dunlop's patent invalidated in favor of Thomson’s patent
• 1892 – Beaded edge tires introduced in the U.S.
• 1894 – E.J. Pennington invents the first balloon tire
• 1895 – Michelin introduced pneumatic automobile tires
• 1898 – Schrader valve stem patented
• 1900 – Cord Tires introduced by Palmer (England) and BFGoodrich (US)
• 1903 – Goodyear Tire Company patented the first tubeless tire, however it was not introduced until 1954
• 1904 – Goodyear and Firestone started producing cord reinforced tires
• 1904 – Mountable rims were introduced that allowed drivers to fix their own flats
• 1906 – First pneumatic aircraft tire
• 1908 – Frank Seiberling invented grooved tires with improved road traction
• 1910 – BFGoodrich Company invented longer life tires by adding carbon black to the rubber
• 1919 – Goodyear and Dunlop announced pneumatic truck tires
• 1938 – Goodyear introduced the rayon cord tire
• 1940 – BFGoodrich introduced the first commercial synthetic rubber tire
• 1946 – Michelin introduced the radial tire
• 1947 – Goodyear introduced first nylon tires
• 1947 – BFGoodrich introduced the tubeless tire
• 1963 – Use of polyester cord introduced by Goodyear
• 1965 – Armstrong Rubber introduced the bias belted fiberglass tire
• 1965 – BFGoodrich offered the first radial available in North America
• 1967 – Poly/glass tires introduced by Firestone and Goodyear
• 1968 – United States Department of Transportation (DOT) numbers required on new tires in USA
• 1974 – Pirelli introduced the wide radial tire

Terms

Tread

The tread is the part of the tire which comes in contact with the road surface. The tread is a thick rubber, or rubber/composite compound formulated to provide an appropriate level of traction that does not wear away too quickly. The tread pattern is characterized by the geometrical shape of the grooves, lugs, voids and sipes. Grooves run circumferentially around the tire, and are needed to channel away water. Lugs are that portion of the tread design that contacts the road surface. Voids are spaces between lugs that allow the lugs to flex. Tread patterns feature non-symmetrical (or non-uniform) lug sizes circumferentially in order to minimize noise. Sipes are valleys cut across the tire, usually perpendicular to the grooves, which allow the water from the grooves to escape to the sides in an effort to prevent hydroplaning.

Treads are often designed to meet specific product marketing positions. High performance tires have small void ratios to provide more rubber in contact with the road for higher traction, but may be compounded with softer rubber that provides better traction, but wears quickly. Mud and snow (M&S) tires are designed with higher void ratios to channel away rain and mud, while providing better gripping performance.

Treadwear

The treadwear grade describes how long the tire manufacturers expects the tire to last. A Course Monitoring Tire (the standard tire that a test tire will be compared to) has a rating of "100". If a manufacturer assigns a treadwear rating of 200 to a new tire, they are indicating that they expect the new tire to have a useful life span that is 200% of the life of a Course Monitoring Tire. In general, manufacturers tend to overstate the treadwear of their tires in an effort to create the impression that their tires last a long time. The ability of manufacturers to report their own numbers makes comparison of treadwear ratings between companies useless. Ratings may still be useful within a manufacturer's own line of tires.

Tread lug

Tread lugs provide the contact surface necessary to provide traction. As the tread lug enters the road contact area, or footprint, it is compressed. As it rotates through the footprint it is deformed circumferentially. As it exits the footprint, it recovers to its original shape. During the deformation and recovery cycle the tire exerts variable forces into the vehicle. These forces are described as Force Variation.

Tread void

Tread voids provide space for the lug to flex and deform as it enters and exits the footprint. Voids also provide channels for rainwater, mud, and snow to be channeled away from the footprint. The void ratio is the void area of the tire divided by the entire tread area. Low void areas have high contact area and therefore higher traction on clean, dry pavement.

Rain groove

The rain groove is a design element of the tread pattern specifically arranged to channel water away from the footprint. Rain grooves are circumferential in most truck tires. Many high performance passenger tires feature rain grooves that are angled from the center toward the sides of the tire. Some tire manufacturers claim that their tread pattern is designed to actively pump water out from under the tire by the action of the tread flexing. This results in a smoother ride in different types of weather.

Sipe

Tread lugs often feature small narrow voids, or sipes, that improve the flexibility of the lug to deform as it traverses the footprint area. This reduces shear stress in the lug and reduces heat build up. Sipes also provide greater traction in wet or icy conditions.

Wear bar

Wear bars (or wear indicators) are raised features located at the bottom of the tread grooves that indicate the tire has reached its wear limit. When the tread lugs are worn to the point that the wear bars connect across the lugs, the tires are fully worn and should be taken out of service.

Contact patch

The contact patch, or footprint, of the tire, is merely the area of the tread which is in contact with the road surface. This is the area which transmits forces between the tire and the road via friction. The length-to-width ratio of the contact patch will affect steering and cornering behavior.

Bead

The bead is that part of the tire which contacts the rim on the wheel. The bead is reinforced with steel wire, and compounded of high strength, low flexibility rubber. The bead seats tightly against the two rims on the wheel to ensure that a tubeless tire holds air without leakage. The bead fit is tight, to ensure the tire does not shift circumferentially as the wheel rotates. The width of the rim in relationship to the tire is a factor in the handling characteristics of an automobile, because the rim supports the tire's profile.

Sidewall

Sidewall worn down to fabric plies due to significant under-inflation

The sidewall is that part of the tire that bridges between the tread and bead. The sidewall is reinforced with rubber and fabric plies that provide for strength and flexibility. The sidewall transmits the torque applied by the drive axle to the tread in order to create traction. The sidewall, in conjunction with the air inflation, also supports the load of the vehicle. Sidewalls are molded with manufacturer-specific detail, government mandated warning labels, and other consumer information, and sometimes decorative ornamentation.

Over time, rubber degrades. Ford has recommended that tires be replaced when they are 6 years old to prevent sudden failure, even if the tire looks undamaged. In tropical climates, such as Singapore, tires degrade sooner than in temperate climates. Tires on seldom-used trailers are at the greatest risk of age-failure, but some tires are built to withstand idleness, usually with nylon reinforcement. In the past rayon was used in tires, but it ages quite quickly.

Shoulder

The shoulder is that part of the tire at the edge of the tread as it makes transition to the sidewall.

Inner tube

Almost all bicycle tires, many motorcycle tires, and many tires for large vehicles such as buses, heavy trucks and tractors are designed for use with inner tubes. Inner tubes are torus-shaped balloons made from an impermeable material, such as soft, elastic synthetic rubber, to prevent air leakage. The inner tubes are inserted into the tire and inflated to retain air pressure.

Wheel

Tires are mounted to wheels that bolt to the hub. The beads of the tire are held on the wheel's rim largely by the internal tire force from the air pressure. Automotive wheels are typically made from pressed and welded steel, or a composite of lightweight metal alloys, such as aluminum or magnesium. These alloy wheels may be either cast or forged.

Valve stem

Valve stem with its cap removed

The valve stem is a tube made of steel or rubber with a metal valve used to inflate the tire with air. Valve stems usually protrude through the wheel for easy access for inflation. Tires are inflated through a valve, typically a Schrader valve on automobiles and most bicycle tires, or a Presta valve on high performance bicycles. The rubber in valve stems eventually degrades. Replacement of the valve stem at regular intervals reduces the chance of failure.

Tire pressure monitoring system

Tire pressure monitoring systems (TPMS) are electronic systems that monitor the tire pressures on individual wheels on a vehicle, and alert the driver when the pressure goes below a warning limit. There are several types of designs to monitor tire pressure. Some actually measure the air pressure, and some make indirect measurements, such as gauging when the relative size of the tire changes due to lower air pressure. These systems are becoming mandatory in countries such as the United States.

Inflation pressure

Tires are specified by the vehicle manufacturer with a recommended inflation pressure, which permits safe operation within the specified load rating and vehicle loading. Most tires are stamped with a maximum pressure rating (for USA only). For passenger vehicles and light trucks, the tires should be inflated to what the vehicle manufacturer recommends, which is usually located on a decal just inside the driver's door, or in the vehicle owners handbook. Tires should not be inflated to the pressure on the sidewall; this is the maximum pressure, rather than the recommended pressure.

If tire pressure is too high, the tire contact patch is reduced, which decreases rolling resistance. However, ride comfort is reduced, but traction is not always reduced, stopping distance is not always increased. Also, going above max sidewall pressure rarely results in the center of the tire wearing more than the shoulder.

If tire pressure is too low, the tire contact patch is increased, increasing rolling resistance, tire flexing and friction between the road and tire. This "under-inflation" can lead to tire overheating, premature tread wear, and tread separation in severe cases. Braking distance did not statistically change as tire pressure increased, suggesting that a larger contact patch from under-inflation may not be a significant contributor for the conditions explored in these specific tests.

Load rating

Tires are specified by the manufacturer with a maximum load rating. Loads exceeding the rating can result in unsafe conditions that can lead to steering instability and even rupture.

Replacing a tire on a vehicle with one with a lower load rating than originally specified by the vehicle manufacturer will often render the insurance invalid.

Speed rating

The speed rating denotes the maximum speed at which a tire is designed to be operated. For passenger vehicles these ratings range from 99 mph (160 km/h) to 186 mph (300 km/h).

Replacing a tire on a vehicle with one with a lower speed rating than originally specified by the vehicle manufacturer will often render the insurance invalid.

Service rating

Tires (especially in the USA) are often given service ratings, mainly used on bus and truck tires. Some ratings are for long-haul, and some for stop-start multi-drop type work. Tires designed to run 500+ miles per day carrying heavy loads require special specifications.

Rotation

Tires may exhibit irregular wear patterns once installed on a vehicle and partially worn. Furthermore, front-wheel drive vehicles will wear the front tires at a greater rate compared to the rears. Tire rotation is the procedure of moving tires to different car positions, such as front-to-rear, in order to even out the wear, thereby extending the life of the tire.

Wheel alignment

When mounted on the vehicle, the wheel and tire may not be perfectly aligned to the direction of travel, and therefore may exhibit irregular wear. If the discrepancy in alignment is large, then the irregular wear will become quite substantial if left uncorrected.

Wheel alignment is the procedure for checking and correcting this condition through adjustment of camber, caster and toe angles. These settings also affect the handling characteristics of the vehicle.

Retread

Tires that are fully worn can be re-manufactured to replace the worn tread. This is known as retreading or recapping, a process of buffing away the worn tread and applying a new tread. Retreading is economical for truck tires because the cost of replacing the tread is less than the price of a new tire. Retreading passenger tires is less economical because the cost of retreading is high compared to the price of a new tire. However, commercial truck drivers run the risk of "blowouts", separation, and tread peeling from the casing, due to reuse of the tire casing. To reduce these problems, tire technicians and the retread plant must ensure the casing is in the best condition possible. Tires or casings with problems such as capped tread, tread separation, corroded belts or sidewall damage, or any run-flat or skidded tires, will be rejected.

In most situations, retread tires can be driven under the same conditions and at the same speeds as new tires with no loss in safety or comfort. The percentage of retread failures should be about the same as for new tire failures, but many drivers, including truckers, are guilty of not maintaining proper air pressure on a regular basis and if a tire is abused (overloaded, under-inflated, or mismatched to the other tire on a set of duals), then that tire (new or recapped) will fail.

Many commercial trucking companies put retreads only on trailers, using only new tires on their steering and drive wheels. This procedure increases the driver's chance of maintaining control in case of problems with a re-treaded tire.

Flat

A flat tire

A flat tire occurs when a tire deflates to the point where the metal of the wheel rim comes to ground level. This can occur as a result of normal wear-and-tear, a leak, or more serious damage. A tire which has lost sufficient pressure to cause it to become distorted at the bottom will impair the stability of the vehicle and may damage the tire further if it is driven in this condition. The tire should be changed and/or repaired before it becomes completely flat. Continuing to drive a vehicle with a flat tire will damage the tire beyond repair, possibly damage the rim and vehicle, and put the occupants and other vehicles in danger. A flat tire or low-pressure tire should be considered an emergency situation, requiring immediate attention to rectify the problem. (Some tires, known as "run-flat" tires, have either extremely stiff sidewalls or a resilient filler to allow driving a limited distance while flat, usually at reduced speed, without permanent damage or hazard.)

Hydroplaning (or aquaplaning)

Hydroplaning, also known as aquaplaning, is the condition where a layer of water builds up between the tire and road surface. Hydroplaning occurs when the tread pattern cannot channel away enough water at an adequate rate to ensure a dry footprint area. When hydroplaning occurs, the tire effectively "floats" above the road surface on a cushion of water - and loses traction, braking and steering, creating a very unsafe driving condition. When hydroplaning occurs, there is considerably less responsiveness of the steering wheel. The correction of this unsafe condition is to gradually reduce speed, by merely lifting off the accelerator/gas pedal.

Hydroplaning becomes more prevalent with wider tires; it is of virtually no concern to bicycle tires under normal riding conditions, as the wheel would have to be turning far faster than any rider is capable of pedaling in order to experience the same phenomenon.

Markings

DOT Code

In the United States, the DOT Code is an alphanumeric character sequence molded into the sidewall of the tire for purposes of tire identification. The DOT Code is mandated by the US Department of Transportation. The DOT Code is useful in identifying tires in a product recall.

The DOT Code begins with the letters "DOT" followed by a plant code (two numbers or letters) that identifies where it was manufactured. The last four numbers represent the week and year the tire was built. A three-digit code was used for tires manufactured before the year 2000. For example, 178 means it was manufactured in the 17th week of 8th year of the decade. In this case it means 1988. For tires manufactured in the 1990s, the same code holds true, but there is a little triangle (?) after the DOT code. Thus, a tire manufactured in the 17th week of 1998 would have the code 178?. After 2000, the code was switched to a 4-digit code. Same rules apply, so for example, 3003 means the tire was manufactured in the 30th week of 2003.

Other numbers are marketing codes used at the manufacturer's discretion.

E-mark

All tires sold for road use in Europe after July 1997 must carry an E-mark. The mark itself is either an upper case "E" or lower case "e" - followed by a number in a circle or rectangle, followed by a further number. An (upper case) "E" indicates that the tire is certified to comply with the dimensional, performance and marking requirements of ECE regulation 30. A (lower case) "e" indicates that the tire is certified to comply with the dimensional, performance and marking requirements of Directive 92/33/EEC. The number in the circle or rectangle denotes the country code of the government that granted the type approval. The last number outside the circle or rectangle is the number of the type approval certificate issued for that particular tire size and type.

Mold serial number

Tire manufacturers usually embed a mold serial number into the sidewall area of the mold, so that the tire, once molded, can be traced back to the mold of original manufacture.

Use classifications

Tires are classified into several standard types, based on the type of vehicle they serve. Since the manufacturing process, raw materials, and equipment vary according to the tire type, it is common for tire factories to specialize in one or more tire types. In most markets, factories that manufacture passenger and light truck radial tires are separate and distinct from those that make aircraft or OTR tires.

Passenger and light truck types

High performance

High performance tires are designed for use at higher speeds, and more often, a more "sporty" driving style. They feature a softer rubber compound for improved traction, especially on high speed cornering. The trade off of this softer rubber is shorter tread life.

High performance street tires sometimes sacrifice wet weather handling by having shallower water channels to provide more actual rubber tread surface area for dry weather performance. The ability to provide a high level of performance on both wet and dry pavement varies widely among manufacturers, and even among tire models of the same manufacturer. This is an area of active research and development, as well as marketing.

Mud and Snow

Mud and Snow, (or M+S, or M&S), is a classification for specific winter tires designed to provide improved performance under low temperature conditions, compared to all-season tires. The tread compound is usually softer than that used in tires for summer conditions, thus providing better grip on ice and snow, but wears more quickly at higher temperatures. Tires may have well above average numbers of sipes in the tread pattern to grip the ice.

Dedicated winter tires will bear the "Mountain/Snowflake Pictograph" if designated as a winter/snow tire by the American Society for Testing & Materials. Winter tires will typically also carry the designation MS, M&S, or the words MUD AND SNOW (but see All-season tires, below).

Studded, highly-siped, winter tire

Some winter tires may be designed to accept the installation of metal studs for additional traction on icy roads. The studs also roughen the ice, thus providing better friction between the ice and the soft rubber in winter tires. Use of studs is regulated in most countries, and even prohibited in some locales due to the increased road wear caused by studs. Typically, studs are never used on heavier vehicles. Studded tires are used in the upper tier classes of ice racing and rallying.

Other winter tires rely on factors other than studding for traction on ice, e.g. highly porous or hydrophilic rubber that adheres to the wet film on the ice surface.

Some jurisdictions may from time to time require snow tires, or traction aids (e.g. tire chains) on vehicles driven in certain areas during extreme conditions.

Mud tires are specialty tires with large, chunky tread patterns designed to bite into muddy surfaces. The large, open design also allows mud to clear quickly from between the lugs. Mud terrain tires also tend to be wider than other tires, to spread the weight of the vehicle over a greater area to prevent the vehicle from sinking too deeply into the mud. However in reasonable amounts of mud and snow, tires should be thinner. Due to them having a thinner wheel base, the tire will have more pressure per square inch on the road surface, thus allowing the tires to penetrate the snow layer and grip harder snow or road surface beneath. This does not compensate when the snow is too deep for such penetration.

All Season

The All Season tire classification is a compromise between one developed for use on dry and wet roads during summer and one developed for use under winter conditions. The type of rubber and the tread pattern best suited for use under summer conditions cannot, for technical reasons, give good performance on snow and ice. The all-season tire is a compromise, and is neither an excellent summer tire nor an excellent winter tire. They have, however, become almost ubiquitous as original and replacement equipment on automobiles marketed in the United States, due to their convenience and their adequate performance in most situations. All-Season tires are also marked for mud and snow the same as winter tires but rarely with a snowflake. Owing to the compromise with performance during summer, winter performance is usually poorer than a winter tire.

All-terrain

All-terrain tires are typically used on SUVs and light trucks. These tires often have stiffer sidewalls for greater resistance against puncture when traveling off-road, the tread pattern offers wider spacing than all-season tires to remove mud from the tread. Many tires in the all-terrain category are designed primarily for on-road use, particularly all-terrain tires that are originally sold with the vehicle.

Spare

Some vehicles carry a spare tire, already mounted on a wheel, to be used in the event of flat tire or blowout. Mini-spare, or "space-saver spare" tires are smaller than normal tires to save on trunk/boot space, gas mileage, weight and cost. Mini-spares have a short life expectancy, and low speed rating.

Run-flat

Several innovative designs have been introduced that permit tires to run safely with no air for a limited range at a limited speed. These tires typically feature strong, load-supporting sidewalls. An infamous example of an alternate run flat technology has plastic load-bearing inserts attached to the rim instead of the reinforced sidewalls.

Heavy duty truck

Heavy duty tires are also referred to as Truck/Bus tires. These are the tire sizes used on vehicles such as commercial freight trucks, dump trucks, and passenger buses. Truck tires are subcategorized into specialties according to vehicle position such as steering, drive axle, and trailer. Each type is designed with the reinforcements, material compounds, and tread patterns that best optimize the tire performance.

Off-the-road (OTR)

OTR tires being transported

The OTR tire classification includes tires for construction vehicles such as wheel loaders, backhoes, graders, trenchers, and the like; as well as large mining trucks. OTR tires can be of either bias or radial construction although the industry is trending toward increasing use of radial. Bias OTR tires are built with a large number of reinforcing plies to withstand severe service conditions and high loads.

Dramatically increasing commodity prices has led to shortages of new tires. As a consequence, multi-million dollar trucks can be idled for lack of tires, costing mines millions of dollars in lost productivity. This has led to a stronger effort to recycle old OTR tires. As of 2008, a new OTR tire can cost up to $50,000; retread tires are sold at half the price of new tires, and last 80% as long. Retreading an OTR tire is labor intensive. First, the retreading technician must place the old tire in a buffing machine to remove what remains of the old tread; "skiving" follows this, which is the removal, by hand, of material the buffing misses. Next, the technician must inspect the tire, repairing defects. Lastly, the technician fills holes in the tire with rubber, applies a cement gum adhesive, and places the tire on a machine which will apply a new tread.

Agricultural

The agricultural tire classification includes tires used on farm vehicles, typically tractors and specialty vehicles like harvesters. High flotation tires are used in swampy environments and feature large footprints at low inflation pressures.

Racing

NASCAR tires

Racing tires are highly specialized according to vehicle and race track conditions. This classification includes tires for top-fuel dragsters, drift racers, extreme off-road racing, oval-track racers, jet-powered trucks, and monster trucks - as well as the large-market race tires for Formula One, NASCAR, rallying, MotoGP and the like. Tires are specially engineered for specific race tracks according to surface conditions, cornering loads, and track temperature. Tires also have been specially engineered for "drifting" in which vehicles engage in exaggerated skids and slides. Racing tires often are engineered to minimum weight targets, so tires for a 500 mile race may run only 100 miles before a tire change. Some tire makers invest heavily in race tire development as part of the company's marketing strategy and a means of advertising to attract customers with racing dreams.

Racing tires often are not legal for normal highway use.

Industrial

Airless tire

The Industrial tire classification is a bit of a catchall category and includes pneumatic and non-pneumatic tires for specialty industrial and construction equipment such as skid loaders and fork lift trucks.

Bicycle

A Cheng Shin brand bicycle tire in the style of a cruiser bicycle

This classification includes all forms of bicycle tires, including road racing tires, mountain bike tires, snow tires, and tubular tires.

Aircraft

Changing a tire on a P-3C Orion aircraft

Aircraft tires are designed to withstand extremely heavy loads for short durations. The number of tires required for aircraft increases with the weight of the plane (because the weight of the airplane is distributed better). Aircraft tire tread patterns are designed to facilitate stability in high crosswind conditions, to channel water away to prevent hydroplaning, and for braking effect. Aircraft tires are usually inflated with nitrogen or helium in order to minimize expansion and contraction from extreme changes in ambient temperature and pressure experienced during flight. Dry nitrogen expands at the same rate as other dry atmospheric gases, but common compressed air sources may contain moisture, which increases the expansion rate with temperature. Aircraft tires generally operate at high pressures, up to 200 psi (13.8 bar) for airliners, and even higher for business jets. Tests of airline aircraft tires have shown that they are able to sustain pressures of maximum 800 psi (55.2 bar) before bursting. During the test the tires have to be filled with water, instead of helium or nitrogen which is the common content of aircraft tires, to prevent the test room being blown apart by the pressure when the tire bursts.

Aircraft tires also include heat fuses, designed to melt at a certain temperature. Tires often overheat if maximum braking is applied during a rejected takeoff or an emergency landing. The fuses provide a safer failure mode that prevents tire explosions by deflating in a controlled manner, thus minimizing damage to aircraft and objects in the surrounding environment.

The main purpose of requiring that an inert gas, such as nitrogen, be used instead of air, for inflation of tires on certain transport category airplanes is prompted by at least three cases in which the oxygen in air-filled tires combined with volatile gases given off by a severely overheated tire and exploded upon reaching auto-ignition temperature. The use of an inert gas for tire inflation will eliminate the possibility of a tire explosion.

Motorcycle

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