How a Tyre is Made

8/8/2019 How a Tyre is Made

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How a Tyre is Made

Tyre manufacturing is a complex technical process, which, for the sake of simplicity can be broken downinto eight manufacturing stages:1) MixingVarious grades of natural and synthetic rubber are blended in an internal mixer (commonly known as aBanbury) and mixed with carbon black and other chemical products. This blend is called the"masterbatch" and its make-up is carefully constructed according to the desired performance parametersof the tyre

2) CalenderingTextile fabric or steel cord is coated with a film of rubber on both sides. Calendered textiles such asrayon, nylon and polyester are used for the casing and the cap plies. Steel cord is used for the belts.3) Tread and Sidewall ExtrusionThe tread and sidewalls are constructed by forming two different and specifically designed compoundsinto tread profiles by feeding the rubber through an extruder. Extruders produce continuous lengths oftread rubber which are then cooled and cut to specific lengths.4) Bead ConstructionThe bead core is constructed by coating plated steel wires, which are wound on a bead former by a givennumber of turns to provide a specific diameter and strength for a particular tyre.5) Tyre BuildingTyre building is traditionally a two-stage process. Although modern tyre factories now use a certainnumber of single-stage building machines, two-stage building is still widely used, particularly for the more

standard sizes. In the first stage, the innerliner, the body plies and the sidewalls are placed on a buildingdrum. The beads are they positioned, the ply edges are turned around the bead core and the sidewallsare simultaneously moved into position. In the second tyre building stage, the tyre is shaped by inflationwith two belts, a cap ply and the tread being added. At the end of this stage the tyre is now known as a"green tyre".6) CuringThe green tyre is now placed in a mould inside a curing press and cured for a specific length of time at aspecific pressure and temperature. The finished tyre is then ejected from the mould.7) TrimmingExcess rubber is removed from the cured tyre on a trimming machine.8) InspectionBefore the tyre is allowed to go to the despatch warehouse, it is inspected both visually and electronicallyfor quality and uniformity.

Tread Pattern Types and Functions

Rib shape : Tread patterns dominated by multiple circumferential grooves.

Advantages include lower rolling resistance plus good directional stability andsteering control thanks to lateral resistance. Rib type patterns are suitable forsustained high speeds thanks to their low levels of heat generation.

Key disadvantages are poor braking & acceleration grip on wet roads.

Application: For paved road surfaces and truck or bus steer axles

Lug shape : Tread patterns with the groove arrangement perpendicular to the circumference of the tyre

The main advantage of lug patterns is excellent braking power and traction.

The biggest disadvantage is a tendency towards high noise when driven at highspeed. Indeed, lug patterns are not suitable for high speed driving due to theirhigh rolling resistance.


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Application: For dirt roads, rear wheels of buses, industrial vehicles and dumptrucks .

Rib-Lug shape : A combination of Rib and Lug designs

Key features are a rib in the centre providing directional control whilst a shoulderlug gives good braking & driving power.

Application: Good for both paved and dirt roads. Usually used in both front &rear wheels of trucks and buses.

Block-shape : Patterns consisting of independent blocks divided by circumferential and lateral grooves.

Block patterns provide good steering control and stability on snow covered andwet roads as well as good water dispersal properties in the wet.

However, because the tread blocks are smaller, tyre wear tends to be heavy.

Application: Suitable for winter or all-season passenger car tyres as well as forthe rear wheel use in ordinary applications.

Asymmetric pattern : Tread patterns which differ on either side of the tyre.

Asymmetric tyres have been designed to optimise the opposing requirements ofdry grip and water dispersal. They are good for high speed cornering due to thegreater contact area which helps reduce treadwear on outside of tyre.

Asymmetric tyres must be positioned them the right way around.

Application: High performance and motorsport tyres.Directional pattern : Tread patterns characterised by lateral grooves on both sides of the tyre which

point in the same direction.

Advantages of directional tread patterns are good driving force and brakingperformance. In particular directional patterns provide good water dispersalmeaning stability on wet roads.

Directional tyres must be mounted in the direction of the tread pattern.

Applications: Passenger car tyre for high speed use


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Load Indices

The load-index figure imprinted on the sidewall of thetyre denotes the maximum load capacity of a tyrewhen driven at maximum speed. A list of load indicesand maximum weights is give below:Li kg Li kg65 290 94 67066 300 95 690

67 307 96 71068 315 97 73069 325 98 75070 335 99 77571 345 100 80072 355 101 82573 365 102 85074 375 103 87575 387 104 90076 400 105 92577 412 106 95078 425 107 97579 237 108 1000

80 450 109 103081 462 110 106082 475 111 109083 487 112 112084 500 113 115085 515 114 118086 530 115 121587 545 116 125088 560 117 128589 580 118 132090 600 119 136091 61592 630

93 650

Speed Ratings

All tyres carry a speed symbol in the form of a letter indicating the maximum speed for which the tyre isintended. The table below shows which speed goes with each letter.

Speed symbol Maximum speedkm/h mph

N 140 87

P 150 93

Q 160 99

R 170 106

S 180 112T 190 118

H 210 130

V 240 149

W 270 168

Y 300 186

Speed categoryMaximum speedkm/h mph

ZR 240 149

and above


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Sidewall Markings

On the sidewall of a tyre you will find various codes and markings. The list below aims to simplify thecoding system and allow you, the user, to understand the valuable information imprinted on the sidewall.Tyre SizesTyre sizes are made up of a number of different numbers and letters. For example tyre size 175/70 R 1382 T is made up of the following information:175 The tyre section width in millimetres

70The aspect ratio in % (the height of the sidewall divided by thetyres width)

R Denotes the tyres construction type - in this case its a radial13 Rim diameter in inches82 Load IndexT Speed RatingTyre AgeTyres carry a three digit age code on the sidewall indicating the month and year of manufacture. Forexample 129 means the tyre was manufactured in December 1999.Other MarkingsM&S- Identifies Mud and Snow tyresDOT Codes- Coding satisfying the requirements of the US Department of Transportation contain amixture of letters and numbers such as DOT DVDE MTA 129

E-Marks- Tyres for sale in the European Community must carry an E -Mark in accordance with ECE Reg30 - eg E4 027550

Aspect Ratio

Aspect ratio is the ratio of a tyres width to its height. A 70 series tyre, therefore, is a tyre whose height isequal to 70% of its width. Lower Profile Tyres hence have lower series numbers.

Low Profile Tyres - Performance Characteristics

Compared to conventional passenger car tyres, low profile car tyres have greater width ratio to cope withthe demands of higher performance vehicles.The key performance advantages are:

Improved handling and grip

More traction and braking powerDisadvantages are:

Increased road noise

A harsher ride


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Less resistance to aquaplaning due to the amount of rubber on the road

Low Profile Tyres - Performance Characteristics

Compared to conventional passenger car tyres, low profile car tyres have greater width ratio to cope withthe demands of higher performance vehicles.The key performance advantages are:

Improved handling and grip

More traction and braking powerDisadvantages are:

Increased road noise

A harsher ride

Less resistance to aquaplaning due to the amount of rubber on the road

Summer Tyres

The main characteristic of the summer tyre is excellent driving and braking performance on both dry andwet roads, in temperatures above freezing throughout the spring, summer, autumn and winter. A simpleblock-shape tread pattern ensures the tyres contact area remains as rigid as possible, ensuringmaximium 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 brakingperformance on winter road surfaces. The tread rubber used in winter tyres provides good friction


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characteristics and suppleness even in low temperatures. At present, winter tyre design is focused towardbraking performance and driving control on icy roads. Recent developments in tyre pattern design andrubber technology have greatly improved winter tyre performance.

All-season TyresThese 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 longerblock-edge for winter usage. More sipes appear in the all-season tyre than summer tyre to improve thebraking and driving performance by maximising the effect of edge. It is important to remember that inregions where winter temperatures are very low and heavy snow falls are frequent, braking performancewill 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.

Tyre Rotation

Tyre wear rates differ depending on the axle on which the tyres are fitted and whether the vehicle is

front or rear wheel drive. To extend the life of your tyres it is advisable to change tyre positions on aregular basis. Different tyre manufacturers may recommend different rotation periods, ranging from 2-6,000 miles. It is advisable to switch tyres from left to right periodically as well as from the back to thefront of the vehicle.Certain high performance tyres are position specific and should not be rotated. If indoubt, contact a specialist tyre dealer.If you are replacing two worn tyres, the new tyres should be fitted on the rear of the vehicle.


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"Up-Stepping" by Fitting Low Profile Tyres

Vehicle performance can be improved without the necessity of changing wheelssimply by selecting a tyre with a lower profile. This means maintaining overall

diameter while lowering aspect ratio and correspondingly increasing the tyre width.Put simply, a tyre with a lower section height and wider tread has better corneringforce and grip, thus improving steering stability.In order to attain the maximum performance out of your vehicle, larger and widerwheels are recommended. Although high performance is our goal, there are certainsafety guidelines that must be observed. This means that wheel size and type, andtyre height and width must fall within certain limits. When selecting a highperformance tyre the following must be observed.ClearanceWheel well clearance must be maintained. Failure to do so would most likelyseverely cut the tyre when turning, if not lead to a puncture. The vehiclemanufacturer can provide the maximum tyre width permissible. Otherwise consult aspecialist high performance tyre dealer.Speedometer ErrorWith a constant wheel diameter, overall tyre diameter will decrease proportionatelywith aspect ratio. This smaller overall diameter will result in speedometer error.Wheel SelectionIt is often the case that new wheels are required. This can be because either alarger rim width and/or larger rim diameter is called for. When choosing highperformance wheels ensure that they have the correct offset and pitch circlediameter (P.C.D.) for your vehicle.Up Stepping to High PerformanceMaximizing your cars performance by selecting a lower profile tyre/larger size rimcombination is referred to as "up-stepping." Plus-one or plus-two tells you how muchlarger the rim size is. This "up-step" approach to improving performance came intobeing because, although it is possible to get higher performance without changingrims, it is often necessary to increase tyre width to the point that steering geometry

is affected, with the result that a change in driving style or habits becomesnecessary.So to fully maximise your vehicles performance (which includes preserving thesteering geometry) the "up-step" approach is highly recommended. By fitting a largerrim, increases in tyre section width are properly managed while correct overalldiameter is maintained. This maximizes cornering force and grip without sacrificingany other handling parameters.

Tyre Safety Tips

1. Do not use tyres with a tread depth of less than 1.6mm. Apart from being illegal, tyres with low levels oftread will slide easily, suffer from extended braking distances and will be more susceptible to rupturing. Inwet conditions the vehicle will aquaplane making braking and handling almost impossible.


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2. Make sure your air pressures are correct. Low air pressure generates heat which can result in therubber and cord separating, which in turn leads to the cord becoming cut and puncturing the tyre. Lowpressure also results in excessive wear on the edge of the tyre, shortening the tyres life. Excessivepressure, meanwhile, results in unpredictable handling in addition to which, if the tyre suffers an impact,its easily ruptured and cut. If you brake hard, the tyre may skid, which reduces tyre life as the centre ofthe tread becomes worn. Check tyre inflation pressures at least twice a month. Always check pressureswhen tyres are cool and maintain the pressure recommended by the vehicle manufacturer.3. Dont drive with damaged tyres. If you drive with materials such as stone in the tread groove, or with anail 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.4. Treat abnormal tyre wear immediately. To assure normal wear you should check air pressures andalignment and rotate the tyres regularly. In addition you should avoid bad driving habits such as suddenacceleration, braking and cornering.5. Check the spare tyre. Make sure you regularly check the spare tyres air pressure, existence/nonexistence of damage and the depth of remaining groove regularly.6. Never mount radial tyres on the same axle as non-radial tyres or radial tyres on the front axle whennon-radial tyres are mounted on the rear axle. These conditions are likely to cause vehicle instabilityresulting in a sudden loss of control and serious injury.7. Check regularly that wheel nuts are securely tightened.8. Never overload your tyres. The maximum load and inflation pressure of the tyres are moulded into thesidewall. Also, remember; the tyre is capable of carrying the maximum load only if it is inflated to itsmaximum air pressure.

9. Do not use detergents or chemicals containing petroleum products for cleaning or polishing your tyres.10. Avoid prolonged use on bad surfaces.11. Never fit used tyres unless you are sure of their past history. Tyres age even if they have not beenused or have only been used occasionally. Cracks in the tread or in the sidewall rubber, sometimesaccompanied by deformation of the carcass, are a sure sign of aging. Have your old tyres checked by atyre specialist so that you can be certain they are still suitable for further use.12. If you get a puncture, stop as soon as possible and change the tyre. Besides the obvious safetyconsiderations, continuing to drive on an under-inflated tyre can cause structural deterioration. Puncturedtyres must always be removed from the wheel to check for secondary damage13. If it is necessary and feasible to repair a tyre, it must be carried out by a tyre specialist as soon aspossible to avoid any structural deterioration. All tyre repairs must be entrusted to a tyre repair specialist .Wheel and Tyre Fitting Check List

Before fitting tyres on aftermarket wheels check:1. that the stud/bolt hole pattern is correct.2. that the wheel fits freely onto the hub withoutinterference and that there are no screws, rivets orretaining clips which may interfere with a firm, flatlocation of the hub against the wheel mountingface.3. that the wheel rotates freely and truly on bothfront and ear hubs

4. when fastened to the hub, that no part of the wheel can make contact withthe brake drums or calipers or any other part of the steering orsuspensionCheck nuts and bolts. Correct fitting is vital. Be sure1. that thethread form is correct (fit nuts without wheels).2. that the nut/bolt seating is


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correct.3. that the stud length is adequate for minimum thread penetration ofapproximately 1 x stud diameter and not too long as to permit "bottoming" ofthe stud in the nut.4. that the threads are rust free and not over-lubricated5.when sleeve nuts are used, that the shank diameter is correct and that thebearing washers are always used.When fitting the tyre

1. make sure that the rim size is compatible withtyre size.2. be wary of scratching the protective lacquercoating (on aluminium wheels and some chrome

wheels). Aluminium corrodes very easily onceexposed to atmosphere, water or chemicals.3. where possible always use the adhesive type ofbalance weight, as these help to avoid scratchingof the wheel finish.Finally Check1. that the wheel and tyre assembly does not contact any part of thesuspension or body work by carrying out full bump and lock to lock testsbefore driving the vehicle away from the fitting bay.Do not take risks. Wheelsecurity is vital. Check with experts if you have any doubt.(

Wheel and Tyre Fitting Check ListBefore fitting tyres on aftermarket wheels check:

1. that the stud/bolt hole pattern is correct.2. that the wheel fits freely onto the hub withoutinterference and that there are no screws, rivets orretaining clips which may interfere with a firm, flatlocation of the hub against the wheel mountingface.3. that the wheel rotates freely and truly on bothfront and ear hubs

4. when fastened to the hub, that no part of the wheel can make contact withthe brake drums or calipers or any other part of the steering orsuspensionCheck nuts and bolts. Correct fitting is vital. Be sure1. that thethread form is correct (fit nuts without wheels).2. that the nut/bolt seating iscorrect.3. that the stud length is adequate for minimum thread penetration of


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approximately 1 x stud diameter and not too long as to permit "bottoming" ofthe stud in the nut.4. that the threads are rust free and not over-lubricated5.when sleeve nuts are used, that the shank diameter is correct and that thebearing washers are always used.When fitting the tyre

1. make sure that the rim size is compatible withtyre size.2. be wary of scratching the protective lacquercoating (on aluminium wheels and some chromewheels). Aluminium corrodes very easily once

exposed to atmosphere, water or chemicals.3. where possible always use the adhesive type ofbalance weight, as these help to avoid scratchingof the wheel finish.Finally Check1. that the wheel and tyre assembly does not contact any part of thesuspension or body work by carrying out full bump and lock to lock testsbefore driving the vehicle away from the fitting bay.Do not take risks. Wheelsecurity is vital. Check with experts if you have any doubt.(

Technical Aspects of Alloy Wheels

Wheel Size


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Two measurements, the Rim Diameter and the Rim Width, normally determine the wheel size. This isbest explained with reference to the diagram shown on the right:

Cross Section of WheelOffset

The Offset of a wheel measures the distance between the wheel centreline and the wheel mountingface and is measured in millimetres. It is extremely important that wheels of the correct offset are used inorder to maintain the correct track of the vehicles.Offset can be Positive or Negative and is best illustrated in the two diagrams on the left. Most Modernvehicles are front-wheel drive, and as such generally require positive offset wheels. The main exceptionto this rule is 4x4 vehicles, which often use negative offset wheels.

ClearanceIt is, of course, extremely important that the clearance of both the vehicle body work andsteering/suspension components are maintained. Failure to do so would most likely cause damage toboth the tyre/wheel assembly as well as the body of the vehicles. Clearance is achieved by selecting awheel of the correct size and type of tyre. Quality alloy wheel suppliers can give such information.

Pitch Circle Diameter (PCD)

The P.C.D. can be defined as the diameter (in millimetres) of an imaginary circle drawn through the

centre of the stud holes on the wheel and/or the vehicle wheel hub.

When new wheels are required, it is essential that they have the correct P.C.D. for the vehicle concerned.

Wheel Location on Hub


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Motor vehicle manufacturers use a central location collar on the stub axle hub in order to accuratelylocate the wheel. The wheel collar diameter varies, depending on the make of vehicle.Many replacement allow wheel manufacturers use an adapter (spigot ring) to vary the diameter of thelocating hole. In this way, a particular wheel can, by changing the spigot ring, be used on a variety ofvehicles.

The adapter/spigot ring arrangement is illustrated in the diagrams to the left.

As an example, TSW Spigot rings should always be fitted without he tapered edge facing the vehicle hub.

This is to allow easy and accurate location of the ring onto the hub collar.

Upstepping to High PerformanceVehicle performance can be maximised by selecting a lower profile tyre and larger wheel diametercombination. Care must be taken to select the appropriate replacement wheel / tyre combination to avoidproblems.For example, it is a legal requirements that the tyre and wheel assemblies stay within the body of the car.

The fitting of larger diameter replacement wheels is referred to as up-stepping. Plus One or Plus Twodenotes how much larger the wheel diameter is.

This approach of up-stepping allows the tyre section width to be increased whilst maintaining the correctoverall diameter. This allows the optimisation of cornering force and grip whilst maintaining the original

gearing of the vehicle. One example of this is:

195/60 R 1414 inch diameterOriginal size

205/50 R 1515 inch diameterPlus One

205/45 R 1616 inch diameterPlus Two

205/40 R 1717 inch diameterPlus Three

All of the above have an overall rolling diameter which is within an acceptable tolerance.

Aspect Ratio


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Aspect ratio is the ratio of section height to section width. It should be noted that in general, tyres with alower section height (i.e. where the aspect ratio is lowered) have a higher cornering force and thereforeimproved performance-handling characteristics.

How a Tyre is Made

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