BRIEF TIMELINE of the History of the TYRE A tyre's DNA as we know it today can be traced back to when Robert Thompson invented the first pneumatic tyre in 1845, he received little attention due to the problems experienced with the use of natural rubbers, which aged and cracked rapidly allowing for the air to pass through easily and in turn deflate. A quick snapshot of the major turning points will show some key milestones in the tyres DNA
The future direction is unknown, but one thing for sure, it will be exciting as it develops
1844 - Charles GOODYEAR develops and patents “vulcanised rubber”
1970 - saw the introduction of the SLICK tyre into racing, this soon led to lower profile tyres that were growing wider by the week. Thought to be outrageous at the time, the wide low profile tyre now commonplace on most cars offering better grip and higher safety.
1888 - John Boyd DUNLOP patents the first Pneumatic tyre for a bicycle
1891 - Edouard & Andre MICHELIN develop the first pneumatic demountable tyre and used on bicycle.
1895 - First use of a Pneumatic tyre on a motor vehicle the “Éclair” by the Michelin brothers
1937 - Patent granted to Michelin for the “METALIC” tyre, which saw 1 layer of steel replace up to 20 plies of cotton. Due to the advent WW II it was decided to hold this technology back until they were certain of the outcome
1951 - Michelin introduces the Metalic tyre at Le Mans 24 Hr race
TYRE PRODUCTION Any tyre manufacturing starts with many kinds of raw materials, including pigments, chemicals, some 30 different kinds of rubber, both natural and synthetic, tyre cord fabrics, bead wire, etc. The production process begins with the mixing of basic kinds of rubber with process oils, carbon black, pigments, antioxidants, accelerators and other additives, each of which contributes certain properties to what is called the master batch compound. Natural rubber is harvested from Rubber trees for their sap or raw latex, this is then processed with additives to allow mixing and also to add to its stability and compatibility with the many other ingredients involved with making a tyre.
The mills feed the rubber between massive pairs of rollers, over and over, mixing and blending the material to prepare the different compounds for the feed mills, where they are slit into strips to become sidewalls, treads, or other parts of the tyre. Still another kind of rubber coats the fabric that will be used to make up the tyre's body. The fabrics come in huge rolls, and they are as specialised and critical as the rubber blends. Several kinds of fabrics are used: polyester, rayon, nylon or more recently Kevlar®. The vast majority of today’s passenger tyres have polyester cord bodies. Another key component is the tyre’s bead. Shaped like a hoop, the bead’s backbone is formed from high-tensile steel wire, which will fit against the car's wheel rim. The strands are aligned into a ribbon and coated with rubber for adhesion, then wound into loops that are wrapped together to secure them until they are assembled with the rest of the tyre. This section of the tyre is very strong, effectively the backbone of a tyres construction.
These ingredients are mixed in giant blenders called Banbury’s. They blend the many ingredients together, producing a black, gum-like material that will be milled again later to allow for air to be forced out of the rubber compound under immense pressure, then run through an extruder to allow a shape for handling to be formed for the future use then in the tyres various components
This rubber material can take several forms. Most often it is processed into identified slabs that will be passed through an extruder, and then located to different tyre component areas of the manufacturing plant. By this it means that even though a tyre is perceived as a rubber tyre, there are various and different rubber compounds used in different parts of the tyre, ie the tread compound, the sidewall, the underlay and also the bead
Radial tyres which account for approx 92% of tyre production today are built on a round drum or cylinder that is part of a tyre-building machine. This tyre-building machine pre-shapes radial tyres into a form very close to their final dimension to make sure the many components are in the proper position before the tyre goes into the mould to be cured or vulcanised.
When building a tyre, the tyre builder starts with a double layer of synthetic gum rubber called the inner liner. The inner liner makes it possible to seal air in a tyre and eliminates the need for an inner tube that once came inside each tire, these are now termed Tubeless tyres.
Next come two layers of ply fabric, which are sometimes referred to as the cords. Two strips called apexes stiffen the area just above the bead. Next, a pair of chafer strips are added. They are this because they resist chafing from the wheel rim when mounted on a car.
Now the tyre builder adds the steel belts that resist punctures and hold the tread firmly against the road. The tread is the last part to go on the tyre.
After automatic rollers press all the parts firmly together, the radial tyre, now called a green tire, is ready for inspection and curing.
Passenger tyres are cured at over 300 degrees for 12 to 25 minutes, sometimes much longer as in the case of large earthmover tyres. As the press swings open, the tyres are popped from their moulds onto a long conveyor that carries them to final finish and inspection.
This is how all the parts come together: the tread and sidewall, supported by the body, and held to the wheel by the rubber-coated steel bead. But whatever the details, the basics are fundamentally the same: steel, fabric, rubber, and lots of work, care, design and engineering.
The curing press is where the tyre will get its final shape and tread pattern. Hot moulds like giant waffle irons shape and vulcanise the tyre. The moulds are engraved with the tread pattern, the sidewall markings of the manufacturer and those required by law. Each press cures two tyres at a time; they usually operate around the clock, twenty-four hours a day.
Inspection is both visual and internal. Some tyres are pulled from the production line and X-rayed. Additionally, quality control engineers regularly cut apart randomly chosen tires and study every detail of their construction that affects performance, ride or safety.
THE BASIC TYRE INGREDIENTS Fabric: steel, nylon, aramid fibre, rayon, fibreglass, or polyester (usually a combination, e.g., polyester fabric in the body plies and steel and fabric in the belts and beads of most radial passenger tyres) Rubber: natural and synthetic (hundreds of polymer types) Other: Reinforcing chemicals carbon black, silica, resins Anti-degradants antioxidants/ozonants paraffin waxes Adhesion promoters cobalt salts, brass on wire, resins on fabrics Curatives cure accelerators, activators, sulphur Processing aids oils, tackifiers, peptisers, softeners As an example a P215/60R16 passenger tyre, a popular size today, weighs in at about 12 kg and has approximately 3 kgs. of 5 different types of synthetic rubber 2.6 kgs. of 8 types of natural rubber together with 1.7 kgs of 8 types of carbon black 1 kgs. of steel cord for belt 0.75 kgs. of polyester and nylon 1.5 kgs. of steel bead wire 1.5 kgs. of 40 different kinds of chemicals, waxes, oils, pigments, etc. Typical percentages of the rubber mix in various types of tyres: Synthetic Rubber vs Natural Rubber as a percentage Passenger Tyre 55% / 45% Racing Tyre 65% / 35% Earthmover Tyre 20% / 80% Light Truck Tyre 50% / 50% FAQ why do they use carbon black ? because natural rubber is a dull yellow colour why do new tyres have painted lines around the tread ? this allow quick identification in the factory as to which tread compound is for which carcass what are all the coloured dots on a tyres sidewall ? balance markers when fitted to a rim
GLOSSARY what does it all mean ?? ALL WHEEL DRIVE System whereby all 4 wheels are constantly engaged ALIGNMENT The caster, camber and toe angles in a vehicle's suspension geometry that are set to a specification by the vehicle manufacturer for handling & wear. ASPECT RATIO The relationship between the section height and section width of a tyre expressed as a percentage of section width ASSYMETRIC TREAD The design of the tread pattern changes from one side of the tread face to the other, in order to have two or more different types of tread patterns on one tyre for better overall performance. AQUAPLANING The accumulation of water in a film under the tread face footprint which causes a tyre to lift from the road surface, losing traction. Aquaplaning is affected by vehicle speed, tread pattern, and water depth. ( also see Hydroplaning) BALANCE The equal distribution of the mass of the tyre and wheel assembly for
smooth driving. Balance is achieved by fitting weights to the wheel to offset uneven weight distribution of the tyre &/or wheel combination.
BEAD An inextensible hoop of high tensile steel wires which effectively forms the backbone of the tyre to allows the tyre to hold onto the rim. BEAD SEAT The inner ledge portion of the wheel rim where the tyre bead rests adjacent to the flange. BELTS The layers of tyre cords usually of rubberised steel wires beneath the tread and stabilises the tread from distortion when cornering, braking, and overall centrifugal forces. BIAS-PLY A type of tyre construction utilising plies (usually rubberised fabric cords) that run diagonally from one bead to the other. One ply is set on a bias in one direction, and following plies are set alternately in opposing directions crossing each other, hence the "cross-ply" tyre. CAMBER The angle between the centreline of the tyre and a vertical line as viewed from the front. CAMBER THRUST A cornering force generated by the tyre's camber. CASING / CARCASS The tyre body, layered plies which form the tyre's structure and give it shape. CASTOR The angle between the vehicle's steering axis and a vertical line, as viewed from the side. COMPOUNDING The combining of five basic ingredients: rubber, carbon black, plasticizers, curing materials, and ozone retardants to form the tread and other "rubber" components of a tyre. CONTACT PATCH The area of the tyre's tread that is in actual contact with the road. CORNERING FORCE The lateral G force generated by a tyre once steered off a straight line, acting in opposition to the centrifugal forces at play.
CROWN The centre area of a tyre's tread. DEFLECTION The difference between a tyre's unloaded or free radius and the loaded radius. DIRECTIONAL The desired directional control for a tyre to roll in it's steered STABILITY direction rather than follow road contours. DIRECTIONAL A tyre designed to rotate in only one direction for maximum TREAD performance, especially on wet roads. INNERLINER Also known as a SAFETY SPARE, developed by Goodyear in 1964, the concept of a tyre within a tyre to act as a safety device in the case of dramatic air loss. FOOTPRINT The area of the tyre's tread that is in actual contact with the ground. FORCE VARIATION Process at manufacturing level to establish the optimum BALANCE balance position of the tyre &/or rim combination
( see Harmonic Marking) FOUR WHEEL DRIVE Drive System whereby either all 4 wheels are engaged for drive or in some cases you can engage or dis-engage the number of wheels that are driving or transmitting power to the ground FWD Front Wheel Drive is a drive system whereby the front axle delivers all the driving function of the wheels HARMONIC MARKING Markings on wheels and tyres that allow match mounting to cancel tyre and wheel runout, minimising vibration. Usually marked in either red, yellow or white HOOP STRENGTH The retention strength inherent in the belt construction of a tyre that provides dimensional stability. HYDROPLANING The accumulation of water in a film under the tread face footprint which causes a tyre to lift from the road surface, losing traction. Aquaplaning is affected by vehicle speed, tread pattern, and water depth. ( also see Aquaplaning) IMBALANCE The condition that exists when a tyre's mass is not evenly distributed around the rolling axis and centreline, causing bounce (static imbalance) or shake (dynamic imbalance). INFLATION PRESSURE The pressure of air inside a tyre, which allows them to carry the vehicle's load. KPA Kilograms per cubic centimetre - used to measure air pressure in a tyre.( also see Psi) KEVLAR Developed by DuPont® for many military applications, used in tyre since the 1980's as a strengthening component LINER OR The thin layer of halo butyl rubber inside a tyre that retains the INNER-LINER inflation air, sometimes called the inner-liner. The vast majority (basically all TUBELESS) of passenger tyres are manufactured with an inner-liner.
LOAD INDEX A numerical code associated with the maximum load a tyre can carry at the speed indicated by its speed symbol. LOAD RANGE A term which is gradually replacing the term "Ply Rating" and which is indicated as Standard Load (SL) and Extra Load (XL) for passenger tyres and Load Range C, D etc. for RV/4WD/light truck tyres. (The carrying capacity of the tyre at specific air inflation pressures.) MIXING TYRES Fitting tyres of different sizes, ratings, or constructions to a vehicle. Mixing should be avoided. Some performance vehicles, however, specify different size tyres on front and rear axles. MOUNTING TYRES The act of fitting tyres to wheel rims. MUD & SNOW TREAD Usually marked as "M&S", this is a tyre with a heavy bar or block tread element design to provide maximum traction in mud or snow conditions. The tyre will be marked M+S on the sidewall. NON DIRECTIONAL A tread pattern designed to rotate in either direction without loss in performance. ( see Uni Directional) NYLON Material used in the construction of a tyre carcass. OVERALL DIAMETER The diameter of an unloaded, inflated tyre measured from the crown of the tread on one side to the opposite side. Also called the outside diameter or OD. OVERINFLATION The condition that exists when a tyre is inflated beyond the pressure that would carry the actual load. OVERLAY Usually of a Nylon fabric, material laid over tyre carcass to ensure tighter packaging and also used to "shrink" the carcass in high performance tyres OVERSTEER Occurs when cornering where the rear of a vehicle tends to slip/skid before the front and rotate in the original direction of travel. POLYESTER Material first used in the early 1960's as Nylon replacement to create better ride qualities PLIES Used to reinforce a tyre's construction, comprising of layers of cord fabric and rubber to provide the strength to needed to support a load and resist deflection. PLY The number of cotton fabric layers used in the construction of a tyre PLY RATING The number of plies used in a tyre's construction that has the same strength qualities as a particular number of cotton fabric plies it replaces PSI Pounds per square inch - used to measure air pressure in a tyre.
( also see KPA) RADIAL The tyre construction utilising plies where the cords run radially from bead to bead under the tread.
RAYON Like Polyester and Nylon, used as a material to add strength and smoothness REVOLUTIONS The measured number of revolutions made by a tyre travelling PER MILE one mile/ kilometre. Noted as RPM RIM The wheel which incorporates the well, seats & flange on which a tyre is mounted. RIM DIAMETER The diameter of the rim bead seats, normally indicated in whole numbers in inches for passenger cars. ROLLOVER Occurs during hard cornering where a tyre sidewall contacts the road surface. ROTATION The systematic movement of tyres from one vehicle position to another to maximise tread life and minimise irregular wear. Usually every 5-10,000 klms RUNOUT The out of roundness of the tyre causing a vibration which cannot be balanced. RUN FLAT A tyre designed to operate with little or no air pressure once punctured. Developed initially in the 1960's with a myriad of versions and styles, the latest fashion is for a tyre designed with a relatively stiff sidewall to allow for the weight of the vehicle to be supported by the tyre. Both distance range
and speed limited while under use. Also of note, vast majority can not be repaired once punctured RIM WIDTH The distance between rim flanges. RWD Rear Wheel Drive where the actual drive of the vehicle is via the rear axle drive system whereby the rear axle delivers all the driving function of the wheels SECTION HEIGHT The vertical distance from the bead edge to centre of the crown in an unloaded tyre. (refer aspect ratio to determine height for each tyre) SECTION WIDTH The distance between a tyre's sidewalls measured at the widest part of the tyre when inflated to a prescribed Psi. measured on a specific rim width. SERIAL NUMBER Combination of letters and numbers moulded into the sidewall of the tyre to allow identification at any time in the future, some are even bar-coded as well SERIES A designation of a tyre's aspect ratio. A tyre with an aspect ratio of 60% is a 60 series tire. SERVICE DESCRIPTION A marking consisting of the load index & speed symbol, ie. 87 S. SHOULDER The edge of a tyre's tread where it joins the sidewall. SIDEWALL The portion of the tyre between the bead and the tread. It is flexible to soak up bumps yet stiff enough to limit tyre rollover. SIPE A small cut in the tread face to encourage water displacement & therefore Improved wet weather use grip
SLICK Generally found in the racing environment, but also fork lifts and some mining applications, where the tread face is smooth with no pattern on it apart from tread depth indicators SLIP ANGLE The variation in degrees between the direction in which a steering wheel is turned and the actual direction of tyre / vehicle under a cornering force. SILICA An additive introduced at the Banbury Mixing process as part of the compound mixture. It's advantages are increased grip and also durability SPEED RATING A letter designation identifying the tyre's high speed durability capabilities. SPIRAL OVERLAY A manufacturing system developed by Dunlop for the carcass of the tyre whereby the wrapping of the radial belts etc are in one continuous strip, and wound on to the tyre carcass in a spiral manner. First developed at Le Mans to ensure the tyres held together at the enormous speeds they encountered, now commonplace in high performance tyres STATIC LOADED Distance from the centre of the wheel and tyre assembly RADIUS when fitted to the vehicle and under load TOE SETTING The difference between the front to rear centreline of a tyre mounted on the same axle. Toe-in means the front centreline have less distance between it and the rear centreline therefore and tyres point inward. Toe-out means the
front centreline distance is greater than the rear centreline therefore the tyres will point outward.
TREAD The face of a tyre designed and compounded for high traction and low wear. TREAD DEPTH The moulded rubber groove in the tread measured in either mm or 32nds / inch from the tread face to the bottom of the tread grooves. TREAD PATTERN The arrangement of blocks, grooves, sipes, and channels designed into the tread to enhance its grip and evacuate water / snow/ mud TREAD VOID The land to sea ratio or tread to groove ratio. Areas in the tread, such as grooves and channels, that encourage water to drain away from the footprint or for mud & dirt to displace under centrifugal force. TREADWEAR The measured life of a tyre's tread. TREADWEAR Moulded as "TWI" on a tyres sidewall, narrow rubber bar moulded into the INDICATOR tread pattern at a height of 1.5 mm indicating when the legal limit of tread life has been reached TUBELESS Part of the tyre's construction, which uses a butyl inner-liner to prevent air leakage into the tyre carcass and eliminates the need for a tube.
UNDER-INFLATION The condition that exists when there is not sufficient air pressure in a tyre to support a specific load. This causes the tyre to operate with excessive deflection, mechanical flexing and generates excessive heat and premature wear rates. UNDERSTEER The effect when cornering where the front of a vehicle tends to slide in the direction you were heading before you turned the steering wheel. UNIDIRECTIONAL A tyre that can be fitted either way on a rim with no adverse effect on grip or performance ( also see Non Directional) "UTQG" Acronym for "Uniform Tyre Quality Grading" a quality rating system developed by the U.S. Department of Transportation (DOT) in the late 1970's to create some system whereby tyres could be compared to each other within a individual manufacturer, not brand to brand WHEEL ALIGNMENT The measuring, analysing, and setting of angles to a predetermined geometric specification to ensure maximum tyre service life, vehicle handling, and safety.
TYRE GRADES : Uniform Tyre Quality Grading System or UTQG Except for snow tyres, the American DOT system requires all manufacturers selling into the US market to grade passenger car and some RV tyres based on three performance factors: tread wear, traction, and temperature resistance. The UTQG rating of each passenger car and RV tyre is listed in a manufacturers Car/Light Truck Tyre Catalogue. Tread Wear More Than 100 - Better 100 - Baseline Less Than 100 - Poorer ( usually only seen on race & competition tyres The tread wear grade is a comparative rating based on the wear rate of the tyre when tested under controlled conditions on a specified government test track. The initial base tyre was rated at "100" therefore a tyre graded 200 would wear twice as long on the government test track as one graded 100. The actual tyre mileage will depend upon their conditions of use and will vary due to driving habits, service practices, differences in road characteristics, speed, load, air pressure and climatic. Note: Tread wear grades are valid only for comparisons within a manufacturer's product line. They are not valid for comparisons between manufacturers. To be used as a guide ONLY. Traction A A - Best B B - Intermediate C C - Acceptable Traction grades represent the tyre's ability to stop on wet surface as measured under the controlled conditions on the specified government test track. The Traction grade is based upon "straight ahead" braking tests; it does not indicate cornering ability or steering response. Temperature A A - Best. B B - Intermediate C C - Acceptable The temperature grades represent the tyre's resistance to the generation of heat when tested under controlled conditions on a specified indoor laboratory test wheel. Sustained high temperatures can cause materials within the tyre's construction to degenerate faster and thus reduce tyre life. Excessive temperatures can usually lead to tyre failure. Also of note is that due to weather conditions experienced in the Northern Hemisphere ie snow, black ice etc, many tyres are developed for that climatic conditions and would usually fail rapidly here in Australia due to the compound and construction requirements of a tyre of this kind. Typically they will have a obvious indicator marked on the sidewall of the tyre to ensure they are used only in the conditions they were intended for ie M&S with a very low tread wear rating ie 80 or lower.
Indicators of Various Wear modes Tread Wear On Both Edges UNDER INFLATION For a tyre, to have too little inflation pressure will reduce tread life through increased tread wear on the outside edges (or shoulders) of the tyre. It also can generate excessive heat which reduces tyre durability. It will also reduce braking efficiency together with an adverse effect on fuel economy through increased rolling resistance with low Psi tyres Tead Wear In Centre OVER INFLATION When a tyre is over inflated, the centre of the tread bears most of the load and wears out faster than the outside edges. Uneven wear reduces the useful life of a tyre. Tread has Cups or Dips WORN PARTS ie shock absorbers, ball joints, springs etc Cupping (also called dipping or scalloping) is more common on front tyres, though rear tyres on FWD can cup as well. Usually a sign that wheels are out of balance or that suspension or steering system parts are worn out. Sawtooth Edges MISALIGNMENT Edges of the tread taking on a sawtooth or feathered appearance is usually caused by erratic scrubbing against the road. Adequate tread depth is essential for proper tyre performance. If you notice a loss or change in wet traction, you may not have enough tread left on your tyres. Once the tread depth reaches 1.5 mm it have lost its effective water displacement capabilities and should therefore be replaced. Tread Wear on One Edge MISALIGNMNET This will be created by either too much toe in (outside face) or toe out (inside face) or the camber being set to extreme negative or positive readings. These will be very noisy and also effect initial steering response and adversely affect the braking efficiency of the vehicle, immediate attention should be given if you notice any of these signs or symptoms
SIZE All tyres must meet the size standards for bead shape, width, diameter and other parameters established by a recognised standardising organisation. World leaders among such organisations are the European Tyre and Rim Technical Organisation (ETRTO) and the U.S.Tyre and Rim Association (T&RA). Both use a partially metric based system. Virtually all passenger tyres on the market today use the rim and tyre sizing, load and inflation system established by these bodies. The several tyre size designations in use today depend on when a vehicle was manufactured and whether it was local production or imported. All tyre- sizing systems used today provide information about a tyre's dimensions.
Among the most important for proper fitment is height, width and load carrying capacity.
P-metric This is the United States version of a metric sizing system established in 1976. P-Metric passenger car tyre sizes begin with "P", which simply means "Passenger". Metric The European tyre sizing system is similar to P-Metric but does not use the "P" designator. Alpha-numeric This system was established in 1968 and is based on the tyre's load carrying capacity, correlated to its overall size. The tyre's capacity and size are indicated by letter designations from "Y" (smallest tyre, lowest capacity) then through the alphabet Z,A,B,C etc to "N" (largest tyre, highest capacity). An example of an Alphanumeric tyre size is BR78-13. "B" shows size/load, "R" indicates radial construction, "78" is the aspect ratio, and "13" is the wheel size in inches. Numeric This is the oldest standardized tyre sizing system for passenger car tyres. When this system was adopted, tyre aspect ratios were either 92 or 82. For example, a 7.00-14 tire has a section width of 7 inches, a rim diameter of 14 inches and an aspect ratio of 92. The low profile equivalent size tyre with an aspect ratio of 82 would be 7.35-14. P PASSENGER This indicates a passenger car tyre. If the first character in the size designation is a "P", the tyre is a "P-Metric" tyre and is engineered to standards set by the T&RA (Tyre and Rim Association). If there is no "P", the tyre is engineered to ETRTO (European Tyre and Rim Technical Organization) standards and is a metric tyre. The standards set by T&RA and ETRTO have evolved together and are virtually interchangeable. SECTION WIDTH These numbers indicate the tyre section width in millimetres. This is the dimension from sidewall to sidewall when inflated. A tyre's section width will vary depending on the rim to which it is fitted. The section width will be larger on a wide rim and smaller on a narrow rim. Therefore, each tyre is measured to specific rim width.
(To convert millimetres into inches, divide by 25.4.)
ASPECT RATIO This two-digit number indicates the tyre's aspect ratio. It compares the tyre's inflated section height, which is the distance from the bead to the tread, to its section width (maximum). An aspect ratio of 65 means that the tyre's section height is 65% of the tyre's section width. For clarity, the section width in millimetres is separated from the aspect ratio by a slash (/). R CONSTRUCTION This letter indicates the type of ply construction in the tyre's casing or carcass. "R" means radial. "D" means diagonal, referring to bias ply tyres. "B" means belted for bias belted ply tyres. RIM DIAMETER The "15" indicates the rim diameter in inches. This is the diameter of the tyre bead, most tyres are built to inch standards for rim diameters. However, some tyres are built to millimetric rim dimensions. Always match the tyre's rim diameter to the wheel rim diameter.
NOTE: A millimetric rim has a different shape than an inch rim. THEY ARE NOT INTERCHANGABLE.
SERVICE The service description is an alphanumeric combination, consisting of two DESCRPTION parts, a number and a letter. In this example "89" is the load index, which represents the load carrying capacity. (All passenger car tyres for sale in the US are marked with their actual load limit in pounds, in Australia this is in
Kgs.). The letter part is the speed symbol, 'H,' in this example. This is the maximum speed for which the tyre is rated at the load specified by the load index.
TYRE PLACARD Tyre speed ratings must exceed the maximum speed capability of the vehicle to which they are fitted. Modern vehicles are equipped with a placard which lists the tyre size fitted to the vehicle during production, plus any options available which would be of equivalent speed & load rating as a minimum. It is important to work within these parameters when replacing the tyres on the vehicle. SERVICE Some tyres carry additional markings related to service. An INDICATORS M&S or M+S designation means the tyre is rated suitable by the manufacturer for mud and snow use. These guidelines and definitions are found in the T&RA manual ALL-SEASON Is a marking which means that the tyre meets M&S/M+S requirements DESIGNATION requirements without the drawbacks of noise and rolling resistance associated with the traditional deep-lug winter tyres. The M&S/M+S designation means that the tyre is suitable for normal all-weather driving applications. Tyres that meet the requirements of the M&S designation have better winter traction compared to those without the M&S symbol. SERIAL NUMBER The serial number moulded into the sidewall can designate amongst other things the manufacturer and plant where the tyre was produced, the tyre line and size, and the week and year the tyre was manufactured. MAXIMUM All passenger tyres are marked on the sidewalls to indicate maximum PRESSURE/LOAD load capacity and maximum inflation pressure. Truck tyres will indicate recommended pressure for maximum loads for both dual and single application.
Additional Information on Light Truck Tyres Tyres for light trucks have other markings besides those found on the sidewalls of passenger tyres. ie "LT" The "LT" indicates the tyre is for light trucks. Max. Load is for Dual Axles and single Axles rated in either Lbs or kg at kPa(psi) Cold This information indicates the maximum load and tyre pressure when the tyre is used either as a single application or as a dual, that is, when four tyres are put on each rear axle (a total of six or more tyres on the vehicle). Naturally this also applies for the maximum load and tyre pressure when the tyre is used as a single. Load Range This information identifies the tyre's load-carrying capabilities and its inflation limits. Snow Tyres In some heavy snow areas, local governments may require true snow tyres, those with very deeply cut tread. These tyres should only be used in pairs or placed on all four wheels. Although these types of tyres rarely come to this country it is wise to understand how they work and also how to recognise them to ensure proper application on the vehicle in question. SPEED RATING TABLE Rating Maximum Speed Q 99 mph or 158 kph S 112 mph or 179 kph T 118 mph or 189 kph U 124 mph or 198 kph H 130 mph or 210 kph V 149 mph or 240 kph W 168 mph or 270 kph Y 186 mph or 300 kph Z Above 149 mph or 240 kph The key to this table is the reading the terminology correctly, while a W and Y speed rated at first glance appear to be higher than the Z rated tyre, they are in fact a lower top speed rated tyre. They are speed limited on their rating, W = max 270KPH and the Y = max 300 KPH, while the Z rated tyre is "above 240 KPH" this is a higher rating as it has no upper limit therefore you will usually find this speed rated designation on vehicles that are capable of speed above 300 KPH.
If for example you are trying to find the correct tyre fitment for a vehicle upgrade then the accepted rule is as follows: minimum requirement is the original equipment fitment, you can increase the load index rating but you can not decrease it under any circumstances CALCULATIONS There are times when you will need to calculate certain parameters of a tyre to ensure you do not exceed vehicle manufacturers +/- percentage allowances for certain systems currently running on the vehicle, ie ABS, Traction Control, 4WD and AWD systems : For the examples below we will use a 205/65R15 as the base tyre size with full tread rated at 8.5 mm tread depth OD (overall diameter) 205mm (section width) multiplied by the aspect ratio (65%) = 133.25 mm Multiply by 2 ( for both sidewalls) = 266.50 mm Divided by 25.4 to convert to inches = 10.49" Add the rim diameter ( 15" ) = 25.49" Multiply by 25.4 to convert back to metric = 647.44 mm OD = 647 mm ( or 25.49") Circumference ( roll out of tyre or distance of 1 revolution) Once you know the OD you simply multiply it by 3.14 = 2033 mm or you can multiply the OD by pie (22/7) Static Loaded Radius SLR (OD of the tyre while under load ) A tyre's static (non moving) radius is only accurate while the vehicle is stopped. A static loaded radius is typically about 44% of the actual tyre's diameter. As the vehicle speed increases, centrifugal force causes the tyre to grow taller. This force will increase the tyre's dynamic (changes while moving) radius. At 70 kph for example, most tyres will have a radius that is very close to 48% tyre's static loaded diameter. This growth will increase further with vehicle speed and can actually exceed half of the tyres static loaded diameter. The static loaded diameter is NOT the same thing as an static unloaded diameter. This is a difficult number to give as speed and load will determine that a different result will be achieved therefore on a individual case by case situation the calculation can be done, but accuracy is limited. Obviously this is an area of much confusion and difficulty in establishing the correct information, usually best left to the in house testing team with each manufacture to generate and publish.
Gearing Change Simply put, this is the variation between one tyre of a certain OD and another tyre of a different OD and the resulting percentage difference. Most vehicle manufacturers work on a maximum of approx 4% variation to allow for transmission, final drive ratios, ABS and Traction Control to operate properly and cater for relatively small tyre OD variations. The aim is to stay within this parameter. SIDEWALL MARKINGS / DESCRIPTIONS Sidewall Marking Description BCS BLACK CIRCUMFERENCIAL SERRATION
RBL RAISED BLACK LETTERS
BL BLACK LETTERS
RWL RAISED WHITE LETTERS BSL BLACK SERRATED LETTERS RRBL RECESSED RAISED BLACK LETTERS BSB BROKEN SERRATED BAND SBL SERRATED BLACK LETTERS ENWL EXTRA NARROW WHITE LETTERS SRBL SERRATED RAISED BLACK LETTERS ROBL RAISED OUTLINED BLACK LETTERS SOWL SLANTED OUTLINED WHITE LETTERS OWL OUTLINED WHITE LETTERS SVSB SLANTED VERTICAL SERRATED BAND OBL OUTLINED BLACK LETTERS VSB VERTICAL SERRATED BAND OGL OUTLINED GOLD LETTERS WL WHITE LETTERS ORBL OUTLINED RAISED BLACK LETTERS WS WHITE STRIPE ORWL OUTLINED RAISED WHITE LETTERS WW WHITE WALL OWL OUTLINED WHITE LETTERS RYL RAISED YELLOW LETTERS
CONSTRUCTION There are many varied and differing construction available in today's marketplace. There are some very good reason for these variations, due to either performance levels and application. With time, we will see more and more specialised construction styles becoming more commonplace in our markets. The forces that will drive this are based around the direction the vehicle manufacturers are taking into the future. 25 years ago front wheel dive was an oddity, today its commonplace, 4WD's were seen on the farm, now they are passenger vehicles. A Falcon/Holden sized car in FWD was unheard of, now it is where the manufacturers are concentrating their efforts to allow better ergonomics inside the vehicle. We find that in the marketplace there are some wild and wonderful concepts out there. There are three basic constructions, Bias, Bias Belted and Radial. Bias belts are laid at 45 degrees on the carcass, similar to an X,hence the normal term "cross ply" Radial The belts are laid at 90 degrees to the carcass, giving a radial appearance Bias Belted Comprising of 2 belts laid as bias or cross ply at 45 deg and 2 belts laid at 90 deg as per a radial At this junction it must be pointed out that it does not stop there, we find that engineers are always designing better ways to ensure better performance from any product and tyres are no exception. Taking this one step further we find that within the main groups for tyre construction, there are a number of sub groups.
o Unidirectional
o Directional
o Asymmetrical
o Directional / Asymmetrical It should also be pointed out that these differing tyre constructions are not new as they were often used as early as the late 1930's early 1940's. Some would say they are out to reinvent the wheel but these concepts have been around for decades, and due to many varied reasons, were used once, if at all, then shelved. Today's motor vehicle demands a higher level of comfort, performance and mileage, amazingly, some of the "latest available technology today" was there all the time, they had just forgotten about it. The constructions that are in the marketplace today are a culmination of years of development, technical know how, and sometimes just good luck. Computer analysis, simulation and fluid dynamic packages allow for greater in house R&D without ever making the tyre in the first place, whereas until say the late 1980's all new tyres were basically trial and error time consuming tests.
To bring a new tyre to the market took back then 4-5 years of development, today this is now in the order of 1-2 years maximum. In this day and age we find that we can have a directional asymmetrical tyre which is positional and axle dependant and also a run flat tyre. The combinations are growing by the day, therefore we must be aware of these development to ensure that tyres are fitted on a vehicle only as intended. Vehicle engineers are develop suspension systems that allow for low profile tyre, for better handling and steering response and decreased braking distances, therefore the suspension is modified to retain the ride comfort demanded by the motoring public. As this trend increases, the low profile tyre will be become more common place, but together with the varying tyre constructions we will see more and more of these unique tyres. Both tyre dealers and the consumer must be vigilant in their recognition of these variations with the tyres and fitments. The tyre suppliers themselves have recognised this and have now with certain tyres in their range decreed that only qualified people can fit them, and then only with a specific machine to ensure total compliance for the tyres application. The basics are as follows:
� be aware of which construction you are fitting to your vehicle
� if in doubt - ask. You can not afford to get it wrong
� be aware of the performance gains / loses on any particular vehicle
� some vehicles suspension is designed around a particular tyre construction
� in changing the basic construction the overall ride quality and vehicle dynamics will change, sometimes this is for the better sometimes it can have an adverse effect
� ensuring the tyre is fitted correctly in accordance with any manufactures
instructions Vehicle manufacturers and engineers are continually striving to create smoother, quieter, better handling cars, tyre manufacturers work hand in hand to achieve this goal, we must all be aware of this technology, the developments, the advancements and any possible disadvantages to ensure you do not detract from the vehicle's engineers overall performance parameters and intentions By far the latest trend we are seeing is the broader application of asymmetrical patterned tyres. These have the advantage of offering two ( sometimes 3) different tread patterns on the same tyre. We are also seeing in Europe in the colder temperatures, twin compound tyres as well, however, there are some pitfalls form this technology in our country that you must be aware of.
Asymmetric tyres come in a few varying forms : Full Asymmetrical tyre Asymmetrical tread Asymmetrical construction Therefore it is usually directional and also has an inside and outside sidewall, usually there is a moulded indicator on the sidewall of the tyre. A full asymmetrical tyre construction has in effect an offset internal tyre construction, working like a hinge as the vehicle enters a corner, to maximise the amount of tread face contact on the road surface. This is to counter the extra forces via load transferred to the tyre as the vehicle enters a corners or changes direction Asymmetrical Treaded tyre Only has an asymmetrical tread pattern Normal case construction Generally used to gain the most amount of traction for the different forces at play while a tyre is rotating versus cornering, however, it still reacts like a "normal" tyre under cornering loads, the biggest advantage of this style of tyre is the improved grip levels say in wet conditions and also minimising noise levels generated by the tyre while in motion Directional Patterned tyre Generally in the shape of a "V" to gain the maximum effect for displacing water offers increased grip factor in the wet, allows for harder compounds to be used while not forgoing grip factors, however, noise levels tend to be higher. Asymmetrical Directional / Positional Tyres At the top end, the UHP range for the seriously fast cars some manufacturers build tyres that are asymmetrical, directional and positional, these are as you would imagine very expensive due to the volume produced, but the advantages for this combination is it allows both the tyre manufacturer and the car manufacturer to be very specific in the specification and make out of the tyre to get the best grip ratios from the design. OVERVIEW The advent of the latest tread and constructional designs are becoming a highly specialised area within the automotive industry. Endeavouring that all end users are aware of which tyre is which, what combinations and constructions can go with each other and primarily to ensure that the vehicle is fitted with the correct tyre to ensure total safety for you, the driver, is our goal.
