HISTORY OF TYRES
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."
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 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.
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.
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.
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.
What can be repaired?
Repairable Area - Definition of Area'T'
Tread repair areas
Radial Ply tyres – Minor Repairs to Radial Tyres for Cars, Vans, and Commercial Vehicles
Cross Ply tyres – Minor repairs to Cross Ply tyres for Cars, Vans, and Commercial Vehicles
Motorcycle & Scooter Cross Ply tyres – Minor Repairs for Tyres Motorcycles and Scooters
The following checks are mandatory before repairing any tyre. (General Requirements of BSAU159f.) This ensures whether a tyre is suitable for repair.
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
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.
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:
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.
How do I know if my tyres are Trading Standards approved?
Check your tyre for an "E" Number. E.g. E4 0213760. This is an ECE type approval mark and number that shows if the tyre has been tested and passed as high quality by the European regulatory authorities.
The very earliest of tyre designs were called Type I and were referred to only by their outside diameter eg 27" which is a common fitment to aircraft such as Harvards or P51 Mustangs.
General Aviation tyres are generally Type III designs and include the most widely used sizes such as 5.00-5 and 6.00-6. These measurements refer to the section width of a tyre and also the rim ledge diameter (or the hole in the middle) hence a 6.00-6 is 6 inches wide and sits on 6 inch wheel.
Three Part Name Sizes cover most of today’s designs and typically describe the Outside Diameter, Section Width and Rim Ledge Diameter. Eg, 15x6.00-6, the tyre is 15 inches tall, 6 inches wide and sits on a 6 inch wheel. Some tyres in this classification are preceded with an ‘H’ which identifies the tyre as having a higher percentage deflection.
Metric sizes are the same as three part name sizes but the Overall Diameter and Section Width are replaced with millimeters but the rim sizes remains in inches, eg 380x150-5, it’s imperial equivalent is a 15x6.00-5.
Radial tyres are also the same as three part name sizes but the dash preceding the rim diameter is replaced with the letter ‘R’ eg 32x8.8R16
RUN FLAT TECHNOLOGY
Flat Tyres Explained
1.Reinforced Tyre Sidewall manufacturers of this include Bridgestone, Dunlop, Goodyear and Pirelli.
2.Rubber clip to your rim manufacturers of this include Michelin. All Run flat technology must operate in tandem with tyre pressure warning systems.
1.Reinforced Tyre Sidewall
Dunlop DSST Tyre
Tyres that carry this technology include the Bridgestone RFT series, Dunlop DSST series, Goodyear EMT series, and the Pirelli Euphori @ series.
2. Rubber Clip to your tyre rim
The rubber clip prevents the tyre rim cutting into your tyre when you experience a loss of pressure. This system has been developed by Michelin and is known as the PAX System. Like the reinforced sidewall it operates in tandem with automated tyre pressure monitors.
WHY DO SOME PEOPLE USE NITROGEN instead of AIR ?
Nitrogen has long been the accepted gas medium for filling aircraft tyres, racing tyres and heavy mining and construction vehicle tyres. Nitrogen is used for safety reasons and to ensure that tyres are always at a constant pressure. Compressed air, the traditional medium for inflating car tyres, contains both oxygen (21%) and nitrogen (78%).
MORE ON WHEELS and TYRES
H up to 130mph
T up to 118mph
V inside tyre size markings (225/50 VR 16) over 130mph
V outside tyre size markings (185/55 R 15 v) up to 150mph
W up to 168mph
Y up to 186mph
Z inside tyre size markings (225/40 ZR 17) over 150 mph
LIST OF POPULAR WHEELS and TYRES:
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