Tyre Notes Ae

8/11/2019 Tyre Notes Ae

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Wheels and Tyres

Topics covered in this presentation:

Tyres

Wheels


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Terminology

Steel WheelsA very popular

design of wheel. Very strong

and cheap to produce.

Alloy WheelsAttractive and

light weight, but can be difficult

to clean.

Spoked WheelsUsed on

older sports vehicles, butcannot be fitted with tubeless

tyres.

Divided rimsthe rims are

made in two halves which are

bolted together, the rims must

never be separated while the

tyre is inflated.

Split rimsthe tyre is held in

place by a large circlip, do not

remove the tyre unless you

have been properly trained

Radial Ply Tyrethe main

plies of the tyre run at 90

degrees from one bead to the

other.

Cross Ply Tyrethe main

plies of the tyre run at 45

degrees from one bead to the

other.

Plies

Layers of strong fabricwhich are built up to give the

tyre its strength and shape

Beadloops of steel which

are the anchorage point for the

plies. Treadthis provides the grip

with the road surface, the

pattern assists in clearing any

water away

Side Wall

this connects thebeads to the tread of the tyre.


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Wheel - Basics

Some vehicles are fitted with alloy

wheels that are made of

magnesium or aluminium.

The pilot bore fits to the hub.

Most standard wheels are made of steel.

The rimholds the tyre.

The wellof the wheel allows the

tyre to be removed and refitted

The centre section iswelded to the rim.

Centre mounting section

Rim

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Valve Stems and Cores Three functionsIt retains the air, it

allows inflation and deflation.

The rubber stem of the valve is

pulled into the wheel.

The valve core contains aspring loaded air valve insert.

The valve core also has a sealing

washer and a seat washer.

The valve cap keeps out

dust and helps keep air in.

Valve caps

Sealing

washer

Seat

washer

Valve stemValve core

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Tyre pressures must only be checked and

adjusted when the tyre is cold


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Wheel studs usually have a

right-hand thread.

If it is a left-hand thread, it can be

marked with L.

Metric threads can be marked with M

or METRIC.

The wheel studs press through

the hub or axle flange.

The taper on the wheel nuts

secures and centres the wheel.

Wheel Fixings

Wheel studs and nuts attach the

wheel to the hub. Taper

Hub flange

Wheel mounting

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Torque

wrench

Wheel Nut Torque

Correct torque of wheel fixing is

vital for all vehicles, and nearly

all require the use of a

torque wrench.

Excessive torque can lead towheel or hub distortion, causing

runout and vibration.

Low torque may allow wheel

nuts to work loose and wheels

to come off.

Nuts should be tightened in a

diagonal pattern.


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Wheel Sizes


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Tyres (Introduction)

Basis Functions The tyre acts as the primary suspension,

cushioning the vehicle from the effects of a

rough surface.

It also provides frictional contact with the road

surface.

This allows the driving wheels to move the

vehicle. The front tyres allows the wheels to steer .

The tyres allow the brakes to slow or stop the

vehicle


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Pneumatic Tyres

The tyre is a flexible casing, which contains air.

Tyres are manufactured from reinforced syntheticrubber.

The tyre is made from an inner layer of fabric plies,

which are wrapped around bead wires at the inneredges.

The bead wires hold the tyre in position on the wheelrim.

The fabric plies are coated with rubber, which is mouldedto form the side walls and tread of the tyre. Behind thetread is a reinforcing band, usually made ofsteel,rayon,or glass fibre. Modern tyres are mostlytubeless, so they have a thin layer of rubber coating

inside to act as a seal.


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Tyre Construction

Cross

ply tyres are not usedon any mass produced modern

cars. However, theconstruction details are usefulto show how tyre technologyhas developed.

Several textile plies are laidacross each other, runningfrom bead to bead in alternatedirections.

The number of plies dependson the size of the tyre and theload it has to carry.

The same number of plies isused on the crown and thesidewalls.


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Tyre Construction

RadialPly tyres consist of a

carcass ply formed by textile

arcs running from one bead to

the other.

Each ply which is laid in an arc

at an angle of 90 degrees to

the direction the tyre rolls.

At the top of the tyre crown

(under the tread), there is a

belt made up of several plies

reinforced with metal wire, laid

on top of the carcass ply.

These crown plies, laid one on

top of the other, overlap at an

angle determined by the type

of the tyre.


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TyreSpecifications

P 205/55 V R 16

TYPEP - PASSENGER

T - TEMPORARY

LT - LIGHT TRUCK

C - COMMERCIAL

WIDTH

(MILLIMETERS)

145-315

ASPECT RATIO

(HEIGHT/WIDTH %)

55, 60, 65 70 ETC

TYPE

B - BIAS-BELTED

D - DIAGONAL BIAS

R - RADIAL

RIM DIAMETER

(INCHES) 13, 14 ETC

P205/55 V R 16P 205/55 V R 16P 205/55 V R 16P 205/55 V R 16P 205/55 V R 16P 205/55 V R 16P 205/55 V R 16

SPEED RATING

B (31 MPH) -

V (150 MPH) -

Z (OVER 150 MPH)

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Special Service Tyre

This is a space-saver spare tyre.

Used to replace flat tyre.

It is not used for rotation(swapping).

It uses a special wheel.

It has no hub caps or wheel covers.

Speed and pressurerestrictions apply.

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Remember the tyre tread depth must be not less than 1.6mm over thecentral three-quarters of the tyre and must go all the way round thecircumference in an continuous unbroken band with no bald patchesanywhere on the tyre tread.

If radial and crossply tyres are fitted to the same vehicle, the radial-plytyres must only be fitted to the rear.

Cross-ply and radial ply tyres must never be fitted to the same axle.

Tyre pressures must be set to the manufactures recommendations

The tread and side wall must be free from large cuts, abrasions or

bubbles


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Wheel imbalance causes wheel

tramp, or hop, makes the tyre

vibrate up and down.

Balance

Centrifugal forces try to throw

heavy areas outward when thewheel is spinning.

Weight must be evenly distributed

around the axis of rotation.

Imbalance can be rectified in one of two

ways by Static Balancing(stationary)

or Dynamic Balancing(spinning).


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Rotation

A system of rotation is used to even out tyre

wear and reduce the need for re-balancing.

(b)5-wheel rotation (including spare).

Radial tyres must be kept on the same

side of the car.

(d)5-wheel radials (including spare).

(a)4-wheel bias (cross-ply) tyre rotation.

(c)4-wheel radial tyre rotation.

(a) (b)

(c) (d)

Care must be taken with spare as some

modern tyres are directional.

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Tyre Notes Ae