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
1844 - Charles GOODYEAR develops and
patents “vulcanised rubber”
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
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.
The future direction is unknown, but one thing for sure, it will be exciting as it develops
©NORTH TERRACE TYRES® 2008
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.
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
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.
©NORTH TERRACE TYRES® 2008
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.
©NORTH TERRACE TYRES® 2008
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, twentyfour hours a day.
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.
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.
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.
©NORTH TERRACE TYRES® 2008
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
Anti-degradants
Adhesion promoters
Curatives
Processing aids
carbon black, silica, resins
antioxidants/ozonants paraffin waxes
cobalt salts, brass on wire, resins on fabrics
cure accelerators, activators, sulphur
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
©NORTH TERRACE TYRES® 2008
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.
©NORTH TERRACE TYRES® 2008
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
STABILITY
The desired directional control for a tyre to roll in it's steered
direction rather than follow road contours.
DIRECTIONAL
TREAD
A tyre designed to rotate in only one direction for maximum
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
INNER-LINER
The thin layer of halo butyl rubber inside a tyre that retains the
inflation air, sometimes called the inner-liner. The vast majority
(basically all TUBELESS) of passenger tyres are manufactured
with an inner-liner.
©NORTH TERRACE TYRES® 2008
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.
©NORTH TERRACE TYRES® 2008
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
SHOULDER
A marking consisting of the load index & speed symbol, ie. 87 S.
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
©NORTH TERRACE TYRES® 2008
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
A letter designation identifying the tyre's high speed durability capabilities.
SPEED RATING
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
TREAD DEPTH
The face of a tyre designed and compounded for high traction and low wear.
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
TREAD VOID
The arrangement of blocks, grooves, sipes, and channels designed
into the tread to enhance its grip and evacuate water / snow/ mud
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.
©NORTH TERRACE TYRES® 2008
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.
©NORTH TERRACE TYRES® 2008
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
B
C
A - Best
B - Intermediate
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
B
C
A - Best.
B - Intermediate
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.
©NORTH TERRACE TYRES® 2008
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
©NORTH TERRACE TYRES® 2008
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 tyresizing 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.)
©NORTH TERRACE TYRES® 2008
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.
©NORTH TERRACE TYRES® 2008
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
Q
S
T
U
H
V
W
Y
Z
Maximum Speed
99 mph or 158 kph
112 mph or 179 kph
118 mph or 189 kph
124 mph or 198 kph
130 mph or 210 kph
149 mph or 240 kph
168 mph or 270 kph
186 mph or 300 kph
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.
©NORTH TERRACE TYRES® 2008
LOAD INDEX TABLE
Load
Index
Pounds
(lbs)
Kilograms
(kgs)
Load
Index
Pounds
(lbs)
Kilograms
(kgs)
60
551
250
93
1433
650
61
567
257
94
1477
670
62
584
265
95
1521
690
63
600
272
96
1565
710
64
617
280
97
1609
730
65
639
290
98
1653
750
66
662
300
99
1708
775
67
677
307
100
1764
800
68
695
315
101
1819
825
69
717
325
102
1874
850
70
739
335
103
1929
875
71
761
345
104
1984
900
72
783
355
105
2039
925
73
805
365
106
2095
950
74
827
375
107
2149
975
75
853
387
108
2205
1000
76
882
400
109
2271
1030
77
908
412
110
2337
1060
78
937
425
111
2403
1090
79
964
437
112
2469
1120
80
990
450
113
2535
1150
81
1018
462
114
2601
1180
82
1047
475
115
2679
1215
83
1074
487
116
2750
1250
84
1102
500
117
2833
1285
85
1135
515
118
2911
1320
86
1168
530
119
2999
1360
87
1201
545
120
3080
1400
88
1234
560
121
3197
1450
89
1278
580
122
3308
1500
90
1323
600
123
3410
1550
91
1356
615
124
3528
1600
92
1389
630
125
3638
1650
rated @ 36 psi Cold inflation
©NORTH TERRACE TYRES® 2008
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
= 25.49"
( 15" )
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.
©NORTH TERRACE TYRES® 2008
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
©NORTH TERRACE TYRES® 2008
The different sidewalls applications for various or different tyres as an example :
The different sidewalls applications for various or different tyres as an example :
BSL - Black Serrated Letters
The distinctive three-dimensional design makes it evident you care about
the look of your tyres.
B01 - Broken Serrated Band
This sidewall accents the sleek styling of the tyre.
B02 - Broken Serrated Band (EMT)
This sidewall accents the sleek styling of the tyre with the EMT logo.
B07 - Solid Black Letters With Angled Serrated Evenly Broken Band
Provides a sophisticated and refined look.
OWL - Outlined White Letters
The noticeable brightness enhances the overall appearance of the tyre.
RBL - Recessed Black Letters
Gives the tyre a subdued elegance.
RWL - Raised White Letters
Vivid bold lettering highlights the aesthetics of the tyre.
RGL - Raised Gold Letters
This design gives the tyre a sportier look.
SBL - Smooth Black Letters
This sidewall places an emphasis on your tyre’s exceptional performance.
VSB - Vertical Serrated Band
Tastefully arranged to look good on any vehicle.
XNW - Extra Narrow White Width 11-18 MM
Attractive sidewall in tune with today’s automobile.
W17 - Outline White Letters With Full Angled Serrated Evenly Broken
Band
Prominent large lettering portrays a superior appearance.
©NORTH TERRACE TYRES® 2008
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.
©NORTH TERRACE TYRES® 2008
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.
©NORTH TERRACE TYRES® 2008
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.
©NORTH TERRACE TYRES® 2008