The tyre was first invented and patented by R W Thomson.  He patented the Pneumatic Tyre in 1845. His first design used a number of thin inflated tubes inside a leather cover. This design actually had its advantages over later designs. It would take more than one puncture to deflate the whole tyre, and varying the pressures could alter the ride conditions.

 

 

 

 

RW Thomson - Tyre Invention 1845

 

 

It was not until the late nineteenth century, 1888, that John Boyd Dunlop invented the Rubber Pneumatic Tyre. Despite these technological breakthroughs the solid rubber tyre continued to be the dominant tyre and it was not until 1889 that the pneumatic tyre caught on.

 

In 1888, Scottish-born John Boyd Dunlop, a prosperous Veterinary Surgeon in practice in Belfast, Ireland, invented the Pneumatic Bicycle Tyre. A group of Irish businessmen from Dublin, realised the potential of the tyre, and, in 1889, together with Mr. Dunlop, formed a syndicate to float what was to become "THE DUNLOP PNEUMATIC TYRE COMPANY."

 

The first pneumatic bicycle tyres to reach Australia arrived in Melbourne in 1889, and within 2 years, the Dunlop Company was established in Europe & North America ( the first pneumatic bicycle tyres to reach North America arrived in New York on Christmas Day, 1890).

In 1893, the Dublin Company opened a Branch Office and Factory in Melbourne, Australia, right in the heart of Melbourne's Chinatown district.

 

 


Since the bicycle was the popular form of transport, and Cycle Racing the most popular sport, the introduction of the pneumatic tyre was an unqualified success. In spite of this, the Dunlop Company ran into financial difficulties and decided to sell its overseas holdings.

 

In 1899, a Canadian syndicate purchased the Australasian interests and floated "THE DUNLOP PNEUMATIC TYRE COMPANY OF AUSTRALASIA LTD as an Australian company, with a capital of 170, 000 Pounds ( $A 340, 000).

 

In 1905, the Company made the first of its many acquisitions with the purchase of its main rival the Barnet Glass Rubber Company.

 

In 1889, John Boyd Dunlop founded the Pneumatic Tyre Company and Booth's Cycle Agency, which were to become the Dunlop Rubber Company Limited.

The company became involved in aviation in 1910, when Dunlop Rubber Company introduced a wire-spoked wheel with a beaded tyre specifically designed for the aviation market.

In 1925, Dunlop formed a separate Aviation Division to produce

 

Dunlop was a Scottish vet living in Belfast. His son Johnny complained that when he rode his bicycle to school the cobbled streets made his bottom sore. Dunlop solved his son's problem by inventing a pneumatic tyre, but then it became clear that this tyre was faster - the lad kept winning cycle races. There was a famous cycle race on the Queen's College playing fields on 18 May 1889 and Dunlop persuaded the cycle champion Willie Hume to use the new tyres. Willie won the race and everybody wanted the tyres, and so the Dunlop Rubber Company was formed.

 

 

 

What Dunlop did not realise was that 43 years earlier another Scot had patented almost the same thing. Robert Thomson, who had been to America, returned to Britain and was given a workshop by his father where he invented all sorts of things. In 1845 Thomson patented what he called aerial wheels. There were no bicycles then, so it would not have been a bicycle tyre that he invented. There were no internal combustion engines either, just a few steam carriages, and otherwise horse-drawn carriages and carts. However, Thomson did some elegant experiments. 

 

He fitted his tyres to a carriage and, in Regent's Park in London, had it pulled side by side with an ordinary carriage. He showed it was much easier to pull the one with pneumatic tyres. All the watching journalists thought it would be slower because the tyres were soft. It was easier to pull and also silent - it did not make the noise of a carriage. The pneumatic tyres were a huge success but there was no market at the time - rubber was very expensive in the 1840s.

 

Robert Thomson is much under-rated. He invented a whole range of things including a fountain pen - possibly the first fountain pen, though there are other claimants. He never became rich and famous, perhaps because he was so far ahead of his time.

 

Dunlop first advertised his tyres in December 1888 in The Irish Cyclist, and in May of the following year the Tyre had its first breakthrough. A Belfast Cycle Race was won on pneumatic rubber tyres, and by now the public were starting to take note.

 

Unfortunately the original tyre had its drawbacks. The inner tube was difficult to get at because the tyre was stuck to the wheel. In 1890 CK Welsh patented the design of a wheel rim and outer cover with inextensible lip. By now we had the basics for today’s tyre. Over the years the tyre has developed into today’s high technology offerings. Two of the most important technical developments include Michelin’s creation of the radial tyre with its vastly superior grip in 1948, and when Dunlop did away with the inner tube on car tyres in 1972.

 

 

 

RW Thomson - Tyre Invention 1845

 

 

Time has given the motor industry tyres capable of many different applications. This ranges from High Speed Racing such as Formula One to Heavy Plant Usage on vehicles as large as a house. All tyres deliver a comfortable ride, relative puncture resistance, wear and performance. The importance of a tyre must not be taken for granted. After all a tyre is your vehicles only point of contact with the road.

 

 

 


 

 

 

TYRE INFLATION PRESSURES

 

Although cars are manufactured to give trouble free motoring over long distances, the tyres should still be checked weekly. Tyres expand when they heat up, and this happens when you start driving, so the best time to check your tyre pressures is first thing in the morning before you leave home. If you do check the pressures during a journey, and they read higher than the normal recommended pressure, do not reduce the pressure. It is less dangerous to drive with over-inflated tyres than it is to do so with under inflated ones. However, the best solution is regular checking to establish the correct pressure at all times.

 

 

Too much

 

If the front tyres on a front wheel drive vehicle are over-inflated, the tyre becomes hard, and the area of tyre in contact with the road is reduced. This then means that the grip of the tyre is also reduced. In bad weather, the steering becomes less positive, and the tyre will wear more in the centre, because of the over-inflation. The same applies on the rear tyres of a rear wheel drive vehicle.

 

 

Too little

 

As we mentioned earlier, it is actually most dangerous to drive a car with under-inflated tyres. The main reason for this is that under-inflation causes the tyre to become less rigid, and consequently offers inferior control to the steering functions, and ironically can cause less of the tyre to be in contact with the road surface. It is equally dangerous to both front and rear tyres to have them under-inflated. Continued use under these circumstances increases the likelihood of the tyre casing breaking, as the internal heat of the tyre will increase due to the lack of sufficient air inside the tyre.

 

Finally, given the increasing environmental concerns facing us all, under-inflated tyres lead to increased fuel consumption.

 

On the side of your tyre, you will see a code. This is an international code, which shows the type of tyre and the specification. Those numbers and letters tell you exactly about your tyre.

 

 

 

 

 

This is what they stand for (from left to right):

 

155 - is the nominal tyre width in millimetres.

 

70 - is the height as a percentage of width, the Profile. In this case (from rim flange to tread) it is 70% of 155mm, or 108mm. 

 

R - means that it is a radial tyre.

 

13 - is the wheel diameter in inches.

 

75 - is the code for the carrying capacity per wheel of the car. Code 75 = 387kg.

 

T - is the maximum speed rating for the tyre. This tyre is rated at 118mph. The full table is below.

 

Never put two different types of tyres on the same axle. Indeed, fitting a radial and a cross ply tyre on the same axle is illegal. It is possible to have radials on the rear and cross ply on the front axles, but not the other way round, and is not recommended. The only exception to this is in the case of temporary use spare tyres.

 

 

 


 

 

WHAT IS THE  'OFFSET'

 

One of the most asked questions, what's the offset closely followed by what is the biggest wheel that can I fit onto my car? The offset is a gauge of how much a wheel will stick out from the arch of a car or how far it will recess into the arch of the car. If the offset is wrong, the wheels will stick out too far and will almost be a like a beach buggy!

 

If you take a wheel and cut it in half and draw a line down the centre of the width of a wheel, the offset would be the distance between the back face (mounting face) of the wheel and the centre line that you have just drawn (shown as a dotted line in the diagram below.

 

 

 

 

 

 

It is very important not to deviate too far from the offset of the wheel originally fitted to the vehicle. In this case Vauxhall engineers developed the 'Negative Scrub Geometry". This gave a offset of -49mm (et49). A wheel of radically different offset can cause serious clearance and handling problems along with accelerated tyre and bearing wear.

 

 

The offset is commonly shown as a et number, i.e.et49. This means the offset is 49mm. The offset is always measured in millimetre's and can normally be found at the back of the wheel or stamped behind the centre cap (if fitted).

 

 

Negative scrub geometry had the intention that if you got a flat tyre you were still able to control the car (so long as you weren't going motorway speeds). So its best to keep as close to the et49 figure as possible.

 

However the bigger the alloy wheel goes, the more difficult it becomes to stay close to the et49. The reason being is that as wheel gets bigger in diameter, it also becomes wider, and so does the tyre that fits it. This is when other items in the wheel arch can begin to foul with the alloy wheel or the tyre. Namely the arch lip of the car and the suspension strut. When this happens the offset must change for the bigger wheel and tyre to fit in the arch. Plus if the car has been lowered, this will have to be considered too as the wheel is now tucked further up in the arch.

 

 

Tips on keeping safe and being prepared

 

Changing a tyre can be a daunting prospect. Here are a few hints that can make life easier when changing a tyre.

  • Gloves – Keep a pair in the car at all times.

  • Bin Liner – Something to put a muddy tyre into. Keeps your car clean.

  • Sturdy Board – If the ground is soft the jack may sink. Use as a stand.

  • Wheel Nuts – Grease threads lightly to allow easy removal.

  • Wheel Nuts – Make sure these are tightened correctly.

  • Wheel Nuts – Correct tightening will allow easier removal next time.

  • Wheel Balancing – Always have this done after repair.

  • Tyre Pressure – Never drive too far or too fast after replacing a tyre until the pressure is checked and at the correct level. Refer to Owners Manual.

  • Spare Tyre – Check and examine condition regularly. 

 

PUNCTURES


It is not always necessary to replace a tyre when punctured. In some cases the tyre can be repaired. 
Here are some basic guidelines.

 

What can be repaired?


(In accordance with British Standards (BSAU 159))
Only certain areas of the tyre can be repaired. This is demonstrated below by Area’T’

Repairable Area - Definition of Area'T' 

 

 

Tread repair areas


 
 
The repairable area 'T' is defined as a percentage of the tyre's nominal section width and this is dependant on the type and size of the tyre.

 

 

 

Radial Ply tyres – Minor Repairs to Radial Tyres for Cars, Vans, and Commercial Vehicles

 

 

AREA T Defined as Percentage of Nominal Section Width

CAR

Up to and including 155mm

60%

Above 155mm to 200mm

65%

Above 200mm

70%

Commercial Vehicle

Up to and Including 225mm

60%

Above 225mm to 305mm

65%

Above 305mm

70%


 

Radial Tyre Limitations: Straight Penetration Damage (After Preparation)

Type Of Tyre

Maximum size of damage at base of injury in Area T

Car

6mm

Commercial Vehicle

10mm


Cross Ply tyres – Minor repairs to Cross Ply tyres for Cars, Vans, and Commercial Vehicles

 

 

AREA T Defined as Percentage of Nominal Section Width

CAR

Up to and including 155mm

60%

Above 155mm to 200mm

65%

Above 200mm

70%

Commercial Vehicle

Up to and Including 225mm

60%

Above 225mm to 305mm

65%

Above 305mm

70%


Diagonal (Crossply) Injury Limitations: Straight Penetration Damage (After Preparation)

Type Of Tyre

Maximum size of damage at base of injury in Area T

Car

6mm

Commercial Vehicle

10mm

 

 

Motorcycle & Scooter Cross Ply tyres – Minor Repairs for Tyres Motorcycles and Scooters

 

 

Area T is defined as 50% of Nominal Section width

Injury Limitations: Straight Penetration Damage

Tyre

Max. Size of Damage

Max. no. of repairs

Up to J Speed Rating

6mm

2

Above J up to V Speed Rating

3mm

1

Above V Speed Rating

-

0

 

 


WHEN CAN A TYRE BE REPAIRED

 

The following checks are mandatory before repairing any tyre. (General Requirements of BSAU159f.) This ensures whether a tyre is suitable for repair.

 

  • Minimum Tread Depth Requirement. (Cars 1.6mm, Truck & Motorcycle 1.0mm)

  • Run-flat Damage

  • Contamination

  • Ageing/deterioration of the rubber

  • Bead/Liner Damage

  • Previous repairs not in accordance with BS159

If any of the above is evident it is recommended that tyre is not suitable for repair. Do not repair it. These are only guidelines, and not an exhaustive list. Basic principles of common sense must be adhered to when deciding upon puncture repair.

 

 

TYRE SIDEWALL INFORMATION - WHAT DOES IT MEAN

 

 

 

 

 

205/50 R15 91V E4 DOT

 

 

At first glance the lettering on the side of the tyre may look complicated. It is not meant to be that way. The lettering explains the exact specification of the tyre you have. In short it tells you anything that you may need to know about your tyre.

 

 

Sidewall Marking

Explanation

205

Width of the tyre in millimetres

50

Height of the tyre sidewall as a percentage of the width. In this case 50% of 205mm. Also know as the aspect ratio.

R

Radial Construction.

15

The diameter of the tyre's inner rim in inches

91

Load Capacity of Tyre (See Load Table). In this case its 615kg

V

 

Speed Symbol. Indicates the max. speed for the tyre at full load. In this case 149.1mph.

E4

ECE type approval mark, which demonstrates the tyre has been tested as high quality by the European Regulatory Authorities. All Tyres sold by Black Circles carry this mark.

 

 

 

SPEED RATING

 

It is IMPORTANT that you check your speed rating before buying your tyres - as choosing a lower tyre speed rating could INVALIDATE your INSURANCE.

 

This is indicated by the speed symbol on the tyre sidewall, and represents the maximum speed that this tyre can sustain at full load. Consult your vehicle manufacturer to check which speed rating your vehicle requires. It is of the utmost importance that you stick to the manufacturer's guidelines. 

 

The tyre speed rating (i.e. S) is the maximum speed for which the tyre is rated. For example, the S rating identifies speeds up to 112 mph.

 

Speed ratings are based on scientific tests where the tyre is run at speeds in 6.2 mph steps in 10 minute increments until the required speed has been met.

 

You will find your speed rating on the side of your tyre at the end of a series of numbers - as follows:

 

 

 

Speed Symbol

Speed Kph

Speed Mph

Car

S

180

111.8

T

190

118.1

U

200

124.3

H

210

130.5

V

240

149.1

W

270

167.8

Y

300

186.4

VR

210+

130+

ZR

240+

150+

Speed Symbol

 

Speed Kph

Speed Mph

Winter/Reinforced

Q

160

99.4

R

150

105.6

Van

N

140

87.0

P

150

93.2

Truck

J

100

62.1

K

110

68.4

L

120

74.6

M

130

80.8

 

 

What is a tyre load rating?

 

The Load capacity of a tyre determines what payload each tyre can carry. It is vital that you check with your manufacturer what capacity should be put on your car. Again in cases insurance can be void if you select the incorrect tyres. The following table shows what Index specification can carry.

 

 

Load index

Load in kg

62

265

63

272

64

280

65

290

66

300

67

307

68

315

69

325

70

335

71

345

72

355

73

365

74

375

75

387

76

400

77

412

78

425

79

437

80

450

81

462

82

475

83

487

Load index

Load in kg

84

500

85

515

86

530

87

545

88

560

89

580

90

600

91

615

92

630

93

650

94

670

95

690

96

710

97

730

98

750

99

775

100

800

101

825

102

850

103

875

104

900

105

925

Load index

Load in kg

106