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Tyre
Structure
• This section will help you identify the main components in a tyre's structure.
• The inner liner is a special air-tight rubber lining attached to the inside
of the tyre, used instead of a tube.
• The tyre sidewall adds rigity yo to the structure, protecting the carcass
and improving ride quality by allowing the tyre to expand and compress with the
terrain.
• The apex helps to minimise bead distortion and reduce impacts to it.
• The tread is the part of the tyre in contact with the road. It not only
has to provide grip and cornering stability but must resist abrasion, cutting,
and impacts, as well as withstand high temperatures.
• The bead fixes the tyre to the rim and secures the end of the cord. It
is coposed of a bead wire and rubber core.
• A tyre groove is a channel within the tread that improves driving stability,
pulling ability, and braking ability.
• A tyre belt is made of steel wire or textile fabric. It acts as a reinforcement,
reducing the impacts sustained from the the road and helping to maintain stability
by widening the tread in contact with the road.
• The tyre shoulder is the section from the edge of the tread to the upper
[art of the sidewall. It needs to offer good heat dispersal
• The tyre carcass is the inner cord of the tyre that supports the weight
and absorbs impact. As such it has to resist fatigue caused by the constant flexing
and compression.
• The chafer prevents direct contact between the wheel rim and the cord to
protect the cord.
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Tyre Tread Design
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Groove
A groove is the sunken part of a tyre's tread. Notably grooves are the fundamental
components in deciding a tyre's quality. The groove improves the braking performance
and driving power of a tyre. Groove depth and design also effects road noise and
the rate of a tyre's treadwear. |
• Sipe
A sipe is a fine groove in the tread pattern. The function of a sipe is to enhance
braking and driving performance, and to provide driving stability and comfort.
In the case of winter tyres it allows grip on icy conditions through the biting
effect of the edge, and also improves braking control wet roads.
• Rib shape : The pattern along the circumference of the tyre
 |
Good
points : Lower rolling resistance. Good directional stability and steering
control thanks to lateral resistance. Suitable for sustained high speeds thanks
to low heat generation.
Bad points : Poor braking & acceleration grip on wet roads. Stress caused
by flex means tread is more susceptible to cracking.
Use : For paved road surfaces and the steering wheels of trucks or buses
|
• Lug shape : The groove pattern perpendicular to the circumference
of the tyre
 |
Good
points : Excellent braking & driving power. Superior traction
Bad points : Noisy at high speed. It's not suitable for high speed driving
because of high rolling resistance.
Use : For dirt roads, rear wheels of buses, industrial vehicles and dump
trucks. |
• Rib-Lug shape : The combination of Rib-shape & Lug-shape
 |
Features
: The rib in the centre provides directional control whilst the shoulder lug
gives good braking & driving power
Use : Good for both paved and dirt roads. Usually used in both front &
rear wheels of trucks and buses. |
• Block-shape : The pattern of independent block, which the groove
is connected with each other
 |
Good points
: Good steering control and stability on snow covered and wet roads. Good
water dispersal properties on wet roads.
Bad points : Tyre wear is heavy as tread blocks are finer.
Use : Suitable for winter or all-season passenger car tyres. Suitable for
back-wheel of Radial tyre of ordinary car |
• Asymmetric pattern : Tread pattern differs on each side
 |
Good
points : Good for high speed cornering thanks to greater contact area. Reduces
treadwear on outside of tyre.
Bad points : You must position them the right way around.
Use : High performance and motorsport tyres |
• Directional pattern : Lateral grooves on both sides point the same
direction
 |
Good
points : Good driving force and braking performance. Good water dispersal
means good stability on wet roads. Correct choice for fast driving styles.
Features : mounted in direction of tread pattern
Use : the passenger car tyre for high speed usage. |
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Tyre
Sidewall Markings
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A.
Manufacturer
B. Indication of American certification, load
and speed
C. Product Name
D. Tube or tubeless
E. Tyre size
F. Indication of structure, load and air pressure
G. Indication of country of origin |
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Tyre Size markings
P 205/75R 15 84 H
| P |
P - Identifies
a tyre designed primarily intended for service on passenger vehicles
T- Identifies a tyre intended for one position "temporary use" as a
spare only. |
| 205 |
Nominal
Section Width (mm) |
| / |
|
| 75 |
Nominal
Aspect Ratio |
| R |
Construction
Code: R-Radial D- Diagonal |
| 15 |
Rim Diameter
Code |
| 84 |
Load Index |
| H |
Symbol Speed |
31 x 10.50 R 15 LT C 109 Q
| 31 |
Nominal
Overall Diameter (Inches) |
| x |
|
| 10.50 |
Nominal
Section Width (Inches) |
| R |
Construction
Code
"-" - Diagonal, "R" - Radial |
| 15 |
Rim
Diameter Code |
| LT |
Light Truck
Tyre |
| C |
Load Range |
| 109 |
Load
index |
| Q |
Speed Symbol |
315
/ 75 R 22.5 154/149 L
| 315 |
Nominal Section
width or Width Code |
| / |
|
| 75 |
Nominal Aspect
ratio (ar=H/S) |
| R |
Construction Code |
| 22.5 |
Nominal rim Diameter
Code |
| 154/149 |
Load Indices (Single/Dual) |
| L |
Speed Symbol |
11.00
R 20 149/146 J
| 11.00 |
Nominal Section
Width or Width Code |
| R |
Construction Code |
| 20 |
Nomnial Rim Diameter
Code |
| 149/146 |
Load Indices (Single/Dual) |
| J |
Speed Symbol |
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Aspect Ratio
| Aspect
Ratio (%) = |
| H |
 |
| W |
|
x 100 |
|
A.
Section Width
B. Rim Diameter
C. Overall diameter
D. Height
E. Product Name
F. Tyre Size
H. Manufacturer name |
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Speed
Ratings
| Tyre
Speed Symbol |
Tyre
Speed Rating |
| km/h |
mph |
| S |
180 |
112 |
| T |
190 |
118 |
| U |
200 |
125 |
| H |
210 |
130 |
| V |
240 |
149 |
| W
(ZR) |
270 |
168 |
| Y
(ZR) |
300 |
186 |
| ZR |
Above
240 |
Above
149 |
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Tyre Choice by Season
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Summer tyres
The main characteristic of the summer tyre is excellent driving and braking performance
on both dry and wet roads, in temperatures above freezing throughout the spring,
summer, autumn and winter. A simple block-shape tread pattern ensures the tyre's
contact area remains as rigid as possible, ensuring maximium grip at all times
by optimising friction with the road surface. If the tyre has any special indication
on it, it means this tyre is for summer usage. |
 |
Winter Tyres
This type of tyre is suitable for snow and ice covered roads. The tread pattern
features a heavily siped, fine-block design with grooves that are deep and wide,
providing excellent driving traction and braking performance on winter road surfaces.
The tread rubber used in winter tyres provides good friction characteristics and
suppleness even in low temperatures. At present, winter tyre design is focused
toward braking performance and driving control on icy roads. Recent developments
in tyre pattern design and rubber technology have greatly improved winter tyre
performance.. |
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All-season
Tyres
These tyres are designed to be used all year round to save having to change the
tyres to suit the season. All-season tyre patterns are more complicated than those
of the summer tyre because of the longer block-edge for winter usage. More sipes
appear in the all-season tyre than summer tyre to improve the braking and driving
performance by maximising the effect of edge. It is important to remember that
in regions where winter temperatures are very low and heavy snow falls are frequent,
braking performance will rarely be 100 percent so it is safer to use winter tyres.
All-season tread designs will provide good all-around traction for varing road
conditions, but still provide good treadwear and tyre noise characteristics.
|
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Tyre
Maintenance
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Tyre Rotation
Tyre wear differs depending on the position where the tyre is located, so to extend
the life of your tyres it is important that you change their positions on a regular
basis. Different tyre manufacturers may recommend different rotation periods,
though as a general rule you should rotate them every 2000 - 3000 miles (approximately
3,000 - 5,000 km.) |
 |
Tread Wear
Indicator
A tyre is a wearing part that will need replacement after a period of time. When
the groove depth reaches 1.6mm you are required by law to replace the tyres. It
is advisable to replace them before they have reached this limit, to benefit from
deeper tread in adverse conditions. |
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Tyre
Catagory
| Radial
tyres are designed so that cord of the carcass is perpendicular to the centre
line, and a strong belt is attached it above for added stability even at high
speed. |
Bias tyres feature
a carcass where the angle of the cord to the centre line is 35 degrees. |
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Tyre
Safety
• You must
not use a tyre which has a tread under 1.6 mm
Tyres with tread under this limit will slide easily, suffer from extended braking
distances and will be more susceptible to rupturing. In wet conditions the vehicle
will aquaplane, making braking and handling almost impossible. Tyres with tread
under this limit are illegal and may lead to a fine or disqualification.
• Incorrect air pressure shortens the life of the tyre
If you drive with low air pressure in your tyre, heat is generated in the tyre.
This can result in the rubber and cord separating, which in turn leads to the
cord becoming cut and puncturing the tyre. Low pressure can wear the edge of tyre
which will shorten the tyre's life.
Excessive pressure results in the tyre becoming unpredictable. If the tyre suffers
an impact, it is easily ruptured and cut. If you brake hard, the tyre may skid,
which reduces tyre life as the centre of the tread becomes worn.
• A damaged tyre can rupture during operation
If you drive with materials such as stone in the tread groove, or with a nail
stuck in the tyre, the tyre can become punctured or ruptured. You should change
the tyre immediately on discovering any damage to avoid any further damage to
the carcass.
• Abnormal tyre wear should be treated instantly
In absence of good maintenance, abnormal wear may occur due to sudden braking.
You should check air pressures, alignment and rotate the tyres regularly. In addition
you should avoid bad driving habits such as sudden acceleration, braking and cornering.
• Check the spare tyre
Make sure you regularly check the spare tyre's air pressure, existence/non existence
of damage and the depth of remaining grooves regularly.
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