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Automobile tires perform two basic functions:
They act as soft cushion between the road and the metal
wheel.
They provide adequate traction (friction) with the road
surface.
Tires must transmit driving, braking, and cornering forces
to the road in both good and bad weather.
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The tires on early vehicles were solid rubber.
Today’s automotive tires are pneumatic, which means they
are filled with air.
Internal air pressure pushes out on the inside of the tire to
support the weight of the vehicle.
Tubeless tires - do not have a separate inner tube. The tire
and wheel form an airtight seal.
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Inner tubes (soft, thin, leak proof rubber liner) that fit
inside the tire and wheel assemblies.
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Beads- two rings that are made of steel wire and encased
in rubber. They hold tire sidewalls snugly against wheel
rim.
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Body Plies- Rubberized fabric and cords wrapped around
beads. They form the carcass, or body of the tire.
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Tread- Outer surface of the tire that contacts the road.
Sidewall- Outer part of the tire that extends from the bead
to the tread. Markings on the sidewall provide information
about the tire.
Belts- Sometimes used to strengthen the body plies and
stiffen the tread. They lie between the tread and plies.
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It is measurement of the amount of friction produced as
the tire operates on the road surface.
A high rolling resistance would increase fuel consumption
and wear.
Rolling resistance can be reduced by higher inflation
pressure, proper tire design, and lighter vehicle.
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Three types of tires that are found on late-model vehicles:
Bias Ply tire – the plies run at an angle from bead to bead.
The angle is reversed from ply to ply. The tread is bonded
directly to the top of the ply.
Bias ply is one of the oldest designs and does not use
belts.
The position of the cords allows the body of the tire to
flex easily. A bias ply tire provides a very smooth ride on
rough roads.
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Is a bias ply tire with belts added to increase tread
stiffness. The plies and belts normally run at different
angles.
The belts do not run around to the sidewalls- they lie
under the tread area only.
Belted bias tire provides a smooth ride and good
traction. It also offers some reduction in rolling
resistance over a bias ply tire.
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Has plies running straight across from bead to bead, with
stabilizer belts directly beneath the tread.
The belts can be made of steel, fiber-glass, or other
materials.
It has very flexible sidewall and a stiff tread, giving it a
very stable footprint(shape and amount of tread touching
road surface). This improves safety, wear , cornering , and
braking.
The tread area does not give or flex as much on rough
roads.
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The sidewall of a tire gives information about tire size, tire model,
load-carrying ability, inflation pressure, number of plies, speed
rating, manufacturer. E.G. P185/45R18
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Tire size- Given in alpha numeric sequence (e.g P 185 or LT 185)
The letter “P” indicates that it is used on passenger car.
The first number 185 gives section width in millimeters.
Notice the next three-digit number: 185.. This number means that
the tire is 185 mm at its section width--that is, from the outside of
the tire wall all the way across to the outside of the opposite wall
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The second Number 80 is the aspect ratio or height to width ratio.
The smaller the number the more squat (wider and shorter).
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This the comparison of the tire’s height (bead to tread distance) and
width (sidewall to sidewall distance).
A 80– series tire, for example, has an aspect ratio of 80; the height of
the tire is 80% of the width. A 70- series tire would be “shorter and
wider”
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The “R” indicates radial tire B indicates belted bias ply
and D indicates bias ply
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The last Number P225/45R18 shows the rim diameter in
inches
14” 15” 16” rim
(not metric value)
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Load rating indicates the amount of weight a tire can carry
at the recommended inflation pressure. Most alpha
numeric tires are load range B. which is a 4 ply tire.
Load
Range
B
Ply
Rating
4
C
6
D
8
E
10
F
12
Abbrevia Max Load
ted
Pressure
B
35 psi (240
kPa)***
C
50 psi (350
kPa)***
D
65 psi (450
kPa)***
E
80 psi (550
kPa)***
F
95 psi (650
kPa)***
***Selected large LT sizes are designed with
reduced maximum load pressures
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Is the maximum allowable sustained road speed a tire can
safely withstand without failure. Speed ratings range from
B ( 50 KM/H) to Z (238 KM/H).
It is important that the speed rating of a tire be higher than
the speed at which it will be driven. It too low of a speed
rating is used, the tire could fail and cause a fatal accident.
Note: automotive industry added W- and Y-speed ratings
for vehicles that have extremely high top-speed
capabilities.
W 168 mph 270 km/h
Y 186 mph 300 km/h
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Are used to indicate a critical amount of tread wear. When
too much tread has worn from the tires, solid rubber bars
will show up across the tread. This means tire replacement
is needed. Legal limit 2/32nds of tread.
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Is an extra wheel and tire assemble that can be installed if
the vehicle has a flat tire.
The spare can be a full size tire or a compact tire.
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Full size spare- is a tire of the same size and type used on
the other 4 wheels of the vehicle. It can be mounted and
used like any other tire.
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Compact spare or space saver- is much smaller than the
normal tire used on the vehicle. It saves space in the trunk
or storage area.
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These tires have a coating of sealing compound applied to
there liners. If an object (nail, screw) punctures the tire, air
pressure will push the soft compound into the hole to stop
air leakage.
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Can detect both high and low tire pressure. In these
systems, wheel sensors are mounted on each wheel.
If tire pressure is not correct, the wheel sensor produces a
radio signal. The signal is picked up by a small receiver
that turns on a dash warning light to inform the driver.
The sensors can be mounted by a band that wraps around
the rim or attached to the valve stem.
Note: be careful when dismounting a tire that has a tire
monitoring sensor. The tire machine can damage the
sensor
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Are design to support the tire while withstanding
loads from acceleration, braking, and cornering. The
can be made from steel, cast aluminum or
magnesium.
Mag. wheels or mags, is a nickname for aluminum or
magnesium wheels
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Commonly used on passenger vehicles because it allows
for easier installation and removal of the tire.
Since the centre of the wheel is smaller or (dropped) than
the rim, the tire bead can fall into the recess.
The other side of the tire bead can be forced over the rim
for removal.
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Has small ridges that hold the tire beads on the wheel
during a tire blowout.(instant rupture and air loss).
Small raised lips around the rim keep the tire beads from
sliding into the drop-centre section.
This improves safety by keeping the tire from coming off
the wheel.
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Vale stem is pressed into a hole in the wheel of a tubeless
tire to allow inflation and deflation. The stem is made from
rubber.
A threaded metal tube is formed into the end of the stem.
The valve core is a spring-loaded air valve that is threaded
into the valve stem. The valve core allows air to be added
to the tire using an air chuck.
When the chuck is removed from the valve stem spring
pressure pushes the valve closed to prevent air leakage.
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They hold the wheel and tire assembly on the vehicle.
They fasten to a special wheel stud. The inner face of the
lug nut is tapered to help centre the wheel on the hub.
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Metric nut- metric threads will be identified with an M or
the word metric on the lug nut.
Left hand nuts- These will be marked with a L on the nut
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Question what manufacture used left hand lug nuts?
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They are small lead weights that are attached to the wheel
rim to balance the wheel-and-tire assembly.
This weights prevent vibration by offsetting a heavy area
of the wheel and tire. They are used in ounces or grams
e.g. 50 grams
Stick-on Mag.
Steel
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Static Balance tire is placed
in its vertical axis on a nonrotating spindle tool. The spot
on the tire where the mass is
greatest is acted on by gravity
to deflect the tooling
downward
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Dynamic Balance These
forces are resolved into static
and couple values for the
inner and outer planes of the
wheel, and compared to the
unbalance tolerance.