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What Is Tyre ?
Tyre is that significant part of the vehicle which carries complete load of it & is made of rubber mixed with other chemicals and vulcanized. The tyre is fitted with steel plies & cords that provide strength to it. The main parts of the tyre body are:

Spine is that part of the tyre which is directly in contact with the ground.

Shoulder is the thicker part of tyre where the spine & side wall joins.

Bead Wire
Bead wire is that rigid part which is inelastic & inflexible and provides strength to the fitment of tire on the rim. The type of tyre and structure of bead rings used, determines the size of bead wire.

Side Wall
As the name suggests tire’s sidewall is that area of the tire which is not in contact with the ground & is in between Shoulder & Bead wire.

The plies construct the body of the tyre, they are made up of several layers of fabrics. The most commonly used fabric is polyester cord. In case of Radial tyres the plies run perpendicularly to the tread whereas in case of Bias tyres they are placed diagonally. Nowadays Radial tyres use steel belt plies for more strength & rigidity. The plies are covered with rubber so that they can easily bond with other components & seal the air. More the number of plies more is the strength of tire counted.

Heel is that part of the tire which is in touch with the rim & it helps tire to be tied right to the rim.

Main Functions Of Tyre
The most important functions performed by the tire are as follows:

Tyre Manufacturing
Raw Material
The main raw materials of the tyre consist of natural rubber, synthetic rubber, carbon black & oil. Natural rubber comprises more than 80% of the raw material used. The rest of the material includes various kinds of reinforced material, which includes compounds of filler substances, oil used as plasticizer, some hardening & vulcanizing agents, various booster chemicals & protective agents. On an average the tyre is being manufactured from 20-30 different components.

All the above mentioned raw materials are properly mixed in an internal mixer, known as Banbury Mixer, at about 120 degree Celsius. The mixing of all the components & chemicals enhances the rubber characteristics.

The compounding of rubber used in the passenger car tyre is different from that used in truck tyre. Similarly the compound used for agricultural & OTR tyres is also different.

The steel cord or textile fabric is woven to create a complex textile which is coated with the rubber film on both sides. Textiles like rayon, nylon and polyester are used for making plies & casing. Steel cord is used for introducing belts.

Tread & Sidewall Extrusion
The tread and sidewalls are constructed by forming two (or more) different and specifically designed compounds into profiles by feeding the rubber through an extruder. Extruders produce continuous lengths of tread rubber, or sidewall rubber, which are then cooled and cut to specific lengths.

Bead Construction
The bead core is constructed by coating plated steel wires, which are wound on a bead former by a given number of turns to provide a specific diameter and strength for a particular tyre.

Tyre Building
Tyre makers assemble the components into green tyres using assembly machinery or commonly called tyre building machine. Tyre building is traditionally a two-stage process. Although modern tyre factories now use a certain number of single-stage building machines, two-stage building is still widely used, particularly for the more standard sizes.

When the components have been drawn onto the belt drum of an assembly machine and the frame of a tyre has been set on the bulkheads of the stretching machine, the machine’s loading wheel transfers the unity formed by the surface and the belt onto the frame.

The frame is then pressurized and stretched to fuse with the above-mentioned unity. This is how a green tyre is manufactured.

The "green tyre" has no tread pattern, no markings. It is simply a bare rubber casing.

“Green Tyre” made is vulcanized at 120-200 degree Celsius in curing press called Bagomatic curing Press. The high steam pressure conducted into the curing pad inside the curing press presses the elastic green tyre against the tread pattern and side texts inside the moulds, giving the tyre its final appearance.

Rice pulp is used to generate steam for this process, and curing process is carried on for 20-70 minutes depending upon the size of tyre being cured.

This is the process of removal of excess rubber from the cured tyre on the trimming machine.

Before the tyre is allowed to go to the dispatch warehouse, it is inspected both visually and electronically for quality and uniformity.

Attention is paid to any faults and defects with the appearance of the tyre in the visual inspection. The machine measures the pattern as well as radial throw and lateral force variation of the tyre.When a tyre has been inspected, it will be tested, labeled and transferred to the warehouse for delivery.

Reading Tyres
The information on the sidewalls of your existing tyres is the first important step in selecting new tyres for your vehicle. It looks something like 195/65R14 82 V. Having this information will make the selection of your next set of tyres a lot quicker and easier.

Typical example: P195/65R14 82 V *A standard tyre has a sidewall height, which is 82% of tyre nominal section width.
*Reducing the % of sidewall height to tread nominal section width (the 'aspect ratio') enables tyres to be wider and put more tread on the road.
*Aspect Ratio is the ratio of sidewall height to nominal section width.

What do all signs mean ?
Tyre Type
The ‘P’ written along with the size of the tyre signifies tyre for ‘Passenger Car’. Similarly ‘LT’ for ‘Light Truck’

Tyre Width
‘195’ in the above mentioned example signifies the tyre section width in millimeters (mm) measured from sidewall to sidewall.

Aspect Ratio
Aspect ratio is defined as the ratio of section height of the tire to section width.

“R” on the tyre sidewall denotes the Radial type of tyre. Similarly “B” denotes the BIAS construction of tyre.

Rim Diameter
The value written after “R” is the wheel/rim diameter in inches.

In some tyres ‘M+S’ is Mud & Snow pattern.

Load Index
This signifies the maximum load in Pounds or Kilograms that a tyre can support when properly inflated. Also the max load (Single/dual) is also mentioned elsewhere on the tyre sidewall.

Code Pounds Kilograms Code Pounds Kilograms Code Pounds Kilograms
60 551 250 82 1047 475 104 1984 900
61 567 257 83 1074 487 105 2039 925
62 584 265 84 1102 500 106 2094 950
63 600 272 85 1135 515 107 2149 975
64 617 280 86 1168 530 108 2205 1000
65 640 290 87 1201 545 109 2271 1030
66 661 300 88 1235 560 110 2337 1060
67 677 307 89 1279 580 111 2403 1090
68 695 315 90 1323 600 112 2470 1120
69 717 325 91 1356 615 113 2536 1150
70 738 335 92 1389 630 114 2601 1180
71 761 345 93 1433 650 115 2679 1215
72 783 355 94 1477 670 116 2756 1250
73 805 365 95 1521 690 117 2833 1285
74 827 375 96 1565 710 118 2910 1320
75 853 387 97 1609 730 119 2999 1360
76 882 400 98 1653 750 120 3087 1400
77 908 412 99 1709 775 121 3197 1450
78 937 425 100 1764 800 122 3306 1500
79 963 437 101 1819 825 123 3418 1550
80 992 450 102 1874 850 124 3528 1600
81 1019 462 103 1929 875 125 3638 1650

Speed Index
The speed index is an alphabetical coding that represents the maximum speed to be acquired by the vehicle. For example: ‘H’ means that the tyre has the maximum speed of 130mph. One should note that it is NOT recommended to exceed the speed limit of the vehicle beyond the speed rating of the tyre. It may prove fatal.

Code mph km/h Code mph km/h
A1 3 5 L 75 120
A2 6 10 M 81 130
A3 9 15 N 87 140
A4 12 20 P 94 150
A5 16 25 Q 100 160
A6 19 30 R 106 170
A7 22 35 S 112 180
A8 25 40 T 118 190
B 31 50 U 124 200
C 37 60 H 130 210
D 40 65 V 149 240
E 43 70 Z over 149 over 240
F 50 80 W 168 270
G 56 90 (W) over 168 over 270
J 62 100 Y 186 300
K 68 110 (Y) over 186 over 300

Tread wear Indicator (TWI) It is the marking located where the tread meets the sidewall. When the tread wears & matches the TWI sign, it is strongly recommended to replace the tyres of the vehicle or re-groove them in time.

Other signs Tyre Age
Before 2000, in 1990’s it was believed that the tyre is manufactured for the life of ten years, hence the old system follows the three digit system in which the first 2 digits represents the week & the 3rd digit represents the year. For example: ‘427’ means 42nd week of 7th year of 1990’s (1997).

Since 2000, this 3 digit coding is replaced by 4 digit coding, whose first 2 digits represent the week & the next 2 digits represent the year. For example: ‘4206’ means 42nd week of the year 2006

“DOT” means the tyre is complaint with all applicable safety standards established by the U.S. Department Of Transportation (DOT). A unique 12 digit serial number is followed by the DOT mark, which is a combination of numbers and letters.

“UTQG” stands for Uniform Tyre Quality Grading, a quality rating system developed by the Department of transportation (DOT). DOT requires the manufacturer to grade tyres based on three performance factors: Tread wear, Traction and Temperature resistance.

Tread Wear
Better – More than 100
Baseline – 100
Poorer – Less than 100

The tread wear grade is based on a 7,200-mile wear test conducted under controlled conditions on a specified government test track. The higher the grade, the longer the expected tire life. Tread wear gradings are given in numbers. For example: A tyre graded 200 would wear twice as long on the government test track as one graded 100. The relative performance of tires depends upon the actual conditions of their use, and may vary due to driving habits, service practices, difference in road characteristics and climate.

A – Best
B – Intermediate
C – Acceptable

The rating is decided at the speed of 40 mph and represents the tyre ability to stop on wet pavement as measured on specific government test surfaces of asphalt and concrete. Due to rough surface & low speed, the tread pattern does not play the vital role in test results. This test neither indicates concerning ability of tyre, nor to resist hydroplaning.

The temperature grades are also described in the same way as that for traction. A (highest) grade, B being the intermediate & C being acceptable. The rating represents the tyre’s resistance to the generation of heat when tested under controlled conditions on a specified indoor laboratory test wheel. Sustained high temperature can cause the material of the tyre to degenerate tyre life and thus reduces tyre life. Excessive tire temperature can lead to fatal tyre failure. The grade C corresponds to a level of performance that all passenger car tires must meet under the Federal Motor Vehicle Safety Standard No. 109. Grades A and B represent higher levels of performance on the laboratory test wheel than the minimum required by law.

Tyre Care & Safety

1). Road Conditions
Following operating conditions significantly influence tyre life both in terms of wear & tear and structural durability.
2). Driving Habits
Careful driving habits will ensure optimum tyre life, unavoidable damages besides avoiding serious road accidents.

Over Speeding – This is the most common habit to drive at high speed and sometimes over the recommended speed rating of the tyre. This results in excessive heating of the tyre, faster wear & hence decrease in life of tyre.

Quick acceleration & braking – Panic start & stop of vehicle also decreases the life of tyre. Sudden acceleration builds up excessive heat & sudden braking results in scrub off a good amount of tread rubber causing faster wear of tyres.

Sharp turns around the corner – Excessive wear can happen from one side of the tyre. One should slow down and take a smooth & slow turn.

Riding over stones & other piercing items – This is bad for the tire structure and causes damage to the tyre plies inside. Try to avoid as much as you can.

Parking on rough surface (pointed stone or bricks) – Always take care of the surface where you are parking your vehicle. Long parking of tyres on such surface causes damage to tyre. Be careful & try to avoid these type of objects to come under the tyre.

Speeding over bad roads & speed breakers – Speeding your vehicle over bad rough surface or over speed breakers causes serious damage to tyre structure and ply. One should slow down on bad roads & speed breakers.

3). Seasonal Effect
1)A country experiences various climatic & weather conditions from region to region, somewhere it is very dry & somewhere it is wet, hot & cold, etc. This variation influences the tyre life in terms of mileage & structural durability.

4). Tyre Pressure
Below shown is the effect of over & under inflated tyre & accurate inflated tyre conditions.

Inflated Tyre

5). Wheel Alignment
1) Wheel alignment is the adjustment of the wheel angles in such a way that all the four wheels are parallel to each other & perpendicular to the ground. The primary function of wheel alignment is to enhance tyre performance & its life. (Wheel alignment is completely different from wheel balancing. Wheel balancing is the condition when weight of the wheel is evenly distributed whereas wheel alignment is the condition when all the four wheels are parallel to each other & perpendicular to the ground. If wheel is not properly balanced, it causes vibration in the vehicle at high speed, whereas if the wheel is not properly aligned it causes wear & tear of tyres.)

To notice if the wheels are not aligned, one should concentrate on following factors:
Alignment involves the adjustment of vehicle’s suspension along with wheels & tyres. There are many factors which are responsible for the hampering of alignment. They are as follows:

Caster is the inclination of the steering pivot in the front or behind direction, to adjust steerability. If the angle is in front then the caster is positive and if it is behind then it is negative caster. Rear wheel drive cars have positive caster and front wheel drive cars have negative caster. Caster is there only for front wheels as only the front wheels steer.

Inflated Tyre

Camber is the inward or outward inclination of the tyres when viewed from front. If the top of the wheel is leaning inwards then the camber is negative and if it is leaning outwards then the camber is positive. The positive camber is present on the front tyres for them to stay in a straight line when driving on a straight road. Rear tyres have zero camber.

Toe measurement is the difference of the lateral distance between the front end of the front tyres and the rear end of the front tyres. Toe-in means front end of the tyre is closer and in toe-out means front end of the tyre is apart.

Inflated Tyre

Ride Height
Ride height is the distance between the vehicle’s frame and the road. During customization any change of measurement in the ride height can hamper the alignment of the suspension and reduce tyre life as well as performance. The chassis height of rear side is always kept more than that on the vehicle’s front side.

Types of Wheel Alignment
There are basically three types of wheel alignment offered for the modern wheels, which are as follows:

Front End Alignment: In this type, only the front wheels are aligned & adjusted.

Thrust End Alignment: Here the alignment of rear wheels is done in accordance to the centre line of the vehicle. If the thrust angle is zero the steering wheel will not be centered and to adjust this thing first the rear toe should be adjusted to the center line and then the front toe.

Four-Wheel Alignment: This is the most common type of alignment in which all the four wheels are aligned & adjusted with respect to the suspension.

Advantages of Wheel Alignment

6). Tyre Rotation
Tire rotation is vital to achieve even tread wear and long tread life. With the front tyres having some positive camber angle, the inner edge of the tyre wears faster, hence swapping a front tyre with the diagonally opposite rear tyre will increase the life of the tyre; the tyre which is now at the rear will wear from the centre as the rear end has no camber. Rotate tires at the vehicle manufacturer’s recommended intervals or at 5,000 - 7,000 miles if not specified.

Tyre Rotation

7). Cleaning Tyres
To ensure that Hamilton Tyres give their best performance and look their best, the user must use a mild soap or detergent and a semi-soft bristle brush. To rinse use clean & plain water.

8). Tire Mounting
1)As tire mounting is a difficult process, it needs to be handled with great care & by professional only. Kindly make sure that the tire diameter matches the rim diameter. Note that the tire being mounted on the rim is of the suitable application. There are some recommendations from HAMILTON which are to be taken care while tire mounting:
9). Tyre Sizing
We strongly recommend that the tyres should be fitted as per the recommendations mentioned on the vehicle manual. For best handling do not mix radial tires with non radials. Mounting tires of different speed ratings, sizes or construction could result in tyre failure. However if tires of different profiles are to be used then note that the wider tires fits to the rear of vehicle.

10). Tyre Wear
It is strongly recommended that the tyre needs replacement when only 2/32” tread depth is remaining. All DOT approved tires in production have a tread wear indicator molded into the tread pattern. This small piece of rubber appears to be a bridge between two tire grooves, but is only 2/32” in height. When the top of this indicator is even with the plain of the tread pattern, the tires should be replaced. Failure to replace tires with tread depths less than 2/32” could result in accidents due to loss of traction.

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