Posts filed under ‘When to Replace your Tyres’

Punctures and “Run-Flats”

I hope that it’s been raining where you are. We needed it.

However, one side effect that can get us involved, is the greater risk of a puncture.

Why? Because wet rubber cuts easier, and is pierced easier, than dry rubber. When the tread rubber is almost gone, then the incidence of punctures increases markedly. A fair statement is that the rate of punctures doubles when there is only the last ten percent of the tread thickness left.

So it’s only flat at the bottom, you are told by unsympathetic observers, while you struggle with over- tightened wheel nuts, and having to unload the boot to find that long neglected spare wheel. And of course, it’s still raining.

So what do you do about it? An ounce of prevention, and all that.

First- is there a spare wheel in the wheel well. Is there a wheel well? Good question. Many modern cars/SUV’s don’t have a spare. They supply a can of gunk to seal the tyre, and get you home. Supposedly.

Not much use though when confronted by the tyre ‘failure’ in the accompanying photographs.
Tyre Puncture

This is what is known as a “run flat failure”. The tyre invariably is on a rear wheel, and has been run in a straight line, deflated, at speed for a considerable distance. The sidewall “knuckles under” midwall where the rotating tyre hits the ground, and the heat and distortion actually melts the reinforcing cords in the tyre casing. So after around 10 km, it fails, disastrously. As the driver of this utility explained, “it happened on the freeway, mate”.
Tyre Puncture

You’d need a pretty big can of gunk to fix that, mate!

Then they started the unenviable task of finding a replacement tyre. Being a utility, it was shod with commercial (or L.T.) tyres, which even though it was a Holden, aren’t always carried by retail tyre stores. Took the whole afternoon.

So make sure that your vehicle has a spare, that it’s got air in it, and can be accessed. It doesn’t matter if your new car has a steel wheel, with a different sized tyre on it, when all the rest are spiffy low profiles on mag wheels- it has been matched and approved for rolling diameter ,and load carrying capacity, and it’s legal.

If it’s a used car, make sure that it’s got a spare. Period!

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May 25, 2010 at 5:55 am 6 comments

Tubeless Tyre Valves

The little rubber and brass valve that holds the air in your tyre, and admits new air, is one of the world’s most successful inventions. William Schraeder designed its fundamentals nearly 120 years ago.

The little “springy thingy”, called the “valve core”, that screws into the brass valve really hasn’t altered all that much in that time, and all you need to remove it and let the air out, is a slotted valve cap. Or you can just depress the little button in the centre and you get the same effect, only slower.

Yet when you buy a new tyre, the fitter always replaces the valve. Why does he bother?

The modern tubeless snap-in valve is compressed into a hole in the rim to provide a seal. A brass stem is adhered to a rubber skin, with a domed shape on the inside of the wheel to prevent it being blown through the hole by the air pressure.

 Over time, the degree of compression is lowered (it doesn’t fit as tightly). It may even crack around the groove in the rubber which lodges in the rim hole due to flexing.

The valve actually flexes as the wheel revolves, particularly if it is a long one designed to protrude past the wheel trim. Ultra-high-speed photographs have shown the valve actually touching the rim at right angles at very high speeds. Also the heat during service causes the bond of the brass to the rubber to deteriorate, and if this bond ruptures, the stem blows out, and the tyre goes down quickly.

So reliability is what it’s all about. It’s much better in the long run to replace it after one tyre life.

You can contribute by using dust caps or valve caps, and giving a blast of air around the valve before you clamp on the air chuck, which you should do monthly. If you suspect a leaking valve, a “dob of spittle” on the end of your finger into the brass stem is the tried and true method. If it bubbles, first check the valve core is tight. If it is, loosen it, let some air our, then retighten to dislodge any dirt that might be there.

If it still leaks, replace the core. Unscrewing the core right out will let all the air out, and coincidentally clean the seat that the “springy thingy” seals on. To do this, you need a slotted metal valve cap, or a valve tool, and a kindly service station operator to assist if needed.

The metal clamp-in valves are different. These are used in some alloy wheels, where the thickness of the metal around the hole is too great for a snap-in type. But they are even more desirable when high speeds are the norm. Unlike a snap-in, they do not flex, and they sandwich two air seal washers under compression to get the air seal. So even though they cost more, they last longer, because it is not as necessary to replace them after every tyre life.

Want to know more? See our “All about tyres” section or our “Inflating Tyres Safely” post.

November 9, 2009 at 9:29 am 2 comments

Good Tyres, Bad Tyres, What’s the Difference anyway?

Because so much of the detail of a tyre is hidden from view, and it doesn’t mean much to the average tyre buyer anyway, the customer feels quite entitled to ask “Why does this tyre cost more than that tyre, and what does the difference mean to me anyway?”

Because more often than not, the tyre is presented in a vertical stack alongside other tyres, the salesperson is quite likely to launch into a comparison of tread and buttress design and width, tread pattern design, accompanied by claims of superior mileage, roadholding, reliability, and “it’s on special this week only” sales presentation. The reason is that either the customer can see these things for themselves, or can conceptualise, or are prepared to accept because the salesman obviously knows more than they do.

The question remains though – “why does this tyre cost more than that tyre?” It’s a valid question from the customer’s point of view. Why do some tyres cost more than others, and is it worth it to buy the more expensive tyre?

So start with “how recent is the design?” Most new tyre designs (sizes, patterns, constructions) are brought into production to meet the requirements of the design engineers of new cars. If they didn’t ask for particular improved tyre attributes, then the design process would stagnate. They drive the improvements, to meet design parameters that they want to incorporate in their new car design. This process goes on worldwide, all the time.

The tyre company, needing their business, designs, qualifies, tests extensively, government certifies their new tyre design, and submit prototypes to the car company for evaluation on their new design car. To this stage, this has cost a great deal of money in technical resources, tooling costs, mould manufacture, and qualifying testing. Then they wait while the car company engineers evaluate their tyres against others from competing tyre companies. So there is no certainty that these prototype tyres will ever see enough of a production run to amortise their development costs.

Remember, each new car has at least 4 new tyres, possibly 5.

So hurrah, at last the car company accepts the tyre for production, and contracts for supply at a particular rate at 12 hour’s notice is arranged, at a price that is barely adequate.

Then, after two to three years, replacement tyres are required by the car buyer from a retail tyre store, in competition with tyres from all over the world in the same size. This is possible because of currency alignments, and because tyres are all made to conform to the same standards regarding size dimensions, speed and load carrying capacity.

But there emerge major differences in appearance, because the car engineers may have specified a quiet riding tyre for a saloon, whereas more eye-appealing tyres from say Europe in the same size may have been designed for a more sporty vehicle; or advertising campaigns, consumer reviews may influence both retailer and buyer; the reputation of the brand definitely carries weight; word of mouth approval; bulk package deals from wholesaler to the retailer; or simply the skill of the salesman in influencing the customer’s choice, based on questioning the customer as to the application of the tyre. Always in the background, is the appeal of low price.

Another 3 years on, another 60000 kilometres, time’s moved on, probably the car’s changed hands, the pattern is no longer available (the moulds do wear out), fashion has changed, tooling costs have been recovered, so the price of the product has been lowered to meet competition and retain market share. Besides, 18 inch wheels have superseded 15 inch- that wasn’t so long ago, was it! Your once newly developed tyre has now become the price leader into the tyre shop so that hopefully you will buy something better, more modern, better performing, more costly.

Tyres are all fat and black, look the same from the outside, they’re almost all truly round these days, and the detail of the construction differences are inside the casing. However, small differences inside add up to small improvements in braking, handling, cornering, steering response (lane changing ability), quietness, and harshness over concrete road joins, durability under high speed/high load conditions, and other measurable improvements. All carry a cost, improvements are small, but when it comes to the crunch, may make a difference to your comfort or wellbeing. Just the design of the tread pattern, the scrambling of the tread elements to break up the noise generated, can add considerably to the cost of the mould. Then you have to have the I.T. expertise to be able to produce the noises the pattern makes on a computer first.

If you buy a bad tyre, it will be with you for a long time.

Tread life isn’t the be all and end all. A survey of Australian motorists some years ago showed that the quality most desired in a tyre was the ability to stop, and handle, in the wet. Perhaps the average motorist is more discerning than they are given credit for!

If you would like to know more, have a look at the blog on www.carbonblack.com.au, and the “All About Tyres” section too.

November 2, 2009 at 4:10 am Leave a comment

Wire Failure – from Ipods to Tyres

FAILURE – not a pretty word is it? Yet I had two failures this week, both due to FATIGUE.

My steam iron cord failed just where it comes out of the rubber tube at the end of the handle, and my I-pod just where the ear bud cord comes out of the plastic.

Why there? The iron had a long rubber tube, and a spring shaped thingy as well wound around it. Yet it still “failed” there. The wires inside were charred, but very fine. The I-pod wires were just fine, and broken, if you get my drift.

Why do they make them out of such fine wire, you were going to ask. Well if they made these flexible leads out of a thicker wire, they would not last long at all. Witness when you want to bend a coat-hanger till it breaks. It doesn’t take long, and it gets quite hot to hold where you’re bending it.

But like the iron and the I-pod, it will always break first where it is being flexed the most. This needs a bit of explanation.

So it is with tyres. If nothing else destroys it, such as road damage, the tyre will fail where it flexes the most. Wrong! It fails first where the greatest differences between flexibility (the tyre sidewall) and rigidity (the bead/lower sidewall); or upper sidewall to tread and belt area exists. It fails due to fatigue because by then, it will have rotated and flexed at these parts of the tyre, on average 30 to 45 million times for a passenger tyre, and 100 to 130 million times for a truck tyre.  Truck tyres go further because they’re inflated harder, so don’t flex as much, though they may have worn out three tread lives by then- tyre speak for been retreaded twice.

After that, the carcass of the tyre is not worth retreading because it is approaching the unreliable stage due to fatigue. Reliability is highly prized- and highly priced you might say.

Passenger tyres go at least twice as far as they used to 30 years ago, so a large chunk of the fatigue life built into the tyre is consumed in the first tread life. This is why retreading of passenger tyres has declined to such an extent. It is also why the motorist should look after his tyre pressures. The flatter or more overloaded the tyre, the more the tyre deflects as it rotates, and eats into its reserves against the ultimate failure- fatigue.

Incidentally, the wires in the steel belts of tyres are cables of wire made up if strands of fine wire, just like in the steam iron. The wires in the bead, which locks the tyre on the rim, don’t flex, so they are more like a coathanger wire. The iron had lasted quite well really- at least the fatigue beat the corrosion inside the steam chamber!

October 27, 2009 at 9:21 am Leave a comment

Here’s the plug! Stuckey Tyre Service

Stuckey Tyre Service is one of Australia’s premier suppliers of car tyres, whether for vintage or motorsport application, or everyday road use. We supply all the major premium tyres. Our sales office and warehouse are located at 828 Sydney Road Brunswick, Australia.

Servicing the demands of Australia’s leading motor racing teams has provided us with unrivalled knowledge of the best performance tyre and wheel combination for every application, road or track. From the most exotic European sports car to the average family sedan, we at Stuckey Tyre Service have a carefully selected range of tyres and alloy wheels to enhance the road performance, safety and appearance of your car.

At Stuckey Tyre Service you can take advantage of the ultimate precision fitting and balancing service where the utmost care is taken with your valuable tyre and wheel purchase. In particular we take great pride in being able to balance a wide variety of specialty wheels including wire wheels for historic applications. The most advanced fitting and balancing equipment is used by skilled technicians whose work is trusted by Australia’s top race drivers at speeds over 300Kpm.

We at CarbonBlack love sending customers to the Stuckey team.

October 22, 2009 at 5:25 am Leave a comment

Should Tyres have a use-By Date?

Channel 7’s “Today Tonight” program on Friday 5th December, picked up on earlier publicity originating from an American T.V. program “Twenty-twenty”. An aggrieved customer in South Australia complained that he had been sold Light Truck tyres that were already 14 years old when fitted. One tyre had separated its steel belts from the tread ring, causing damage to his mudguard, and raised the risk of an accident.

The British Rubber Manufacturers have recommended that tyres more than six years old should not be sold, but there is no law requiring this anywhere in the world at present. The American Rubber Manufacturers Association states that there is no scientific evidence to support a six-year limitation on the life of a tyre.

The Channel 7 program cut pieces from the sidewall of the tyre, and did a “tensile test”, pulling on the test piece till it broke. Pieces cut from the (used) 14 year old tyre broke at a lower tensile than from a new tyre. Why they tested the sidewalls, which are a different rubber compound to the tread/steel belt area, it is not known, but it is not surprising that testing two tyres made 14 years apart would give different test results. The reason? The tyres were different!

Tyres are warranted for their life by the manufacturer. Occasionally tyres, like many products, are subjected to a recall program. To enable identification of these, a code is branded into the sidewall, which is used world wide, and is a requirement of the American Department of Transportation. It is called the DOT code. Practically all tyre manufacturers worldwide use this code.

The code details the actual factory in which the tyre was made, the design, and among others items, the last appearing group lists the week and year the tyre was made. 3 digits for the ninetees, four digits for the noughties. Examples then are 489 for the 48th week of 1989, 2604 the 26th week of 2004.

Tyres are generally 6 months to 2 years old by the time they are fitted to your car as replacements. The original equipment tyres are generally one week to six months old, dependent on whether the car was made here, or imported.

The Australian tyre market is so fragmented, with many makes and models of vehicles sold, that the supply chain for replacement tyres is very long, and large stocks are held at distribution points to meet market requirements. For example, the 11 hectare distribution centre at Somerton, Victoria, can hold up to 11 million tyres. Naturally, efforts are made through inventory control to ensure quick turnaround of stock going into the store, to reduce holding costs.

Eventually, tyres are shipped out to your local tyre store. Here they should be stored in racks, in a “cool, dry place”. Many tyre storage areas paint their tyre storage area windows with blue paint to screen out U.V. This is because tyres get harder with age. The vulcanisation process continues at a very slow rate, and protective agents such as antioxidants and antiozidants incorporated into the mix diminish in effectiveness with prolonged storage. Walk into a darkened tyre store, and you can smell the rubber. A somewhat doubtful farming practice used to be that tractor tyres were stored by the farmer to “harden them up”, and possibly improve tread wear. Really, all it did was increase the risk of buttress cracking.

Unless stored correctly (read “All About tyres/Storing a tyre” on our http://www.carbonblack.com.au site), the tyres will eventually craze or crack most severely where the tyre is resting on the pipe rack. This is because stretched rubber is attacked by ozone in the air. Ozone is generated by electric motors and lightning, so maybe the shop compressor is the culprit. However, tests done in the past have never been able to show that tyres stored this way will not give a satisfactory life. The deformations caused by the pipe rack run out as soon as the tyre gets run in on the vehicle- say 10 kilometres, depending on the temperature.

The real sleeper in all this is your spare wheel. Stored in the boot, or under the tray of a light truck, it is subjected to high summer temperatures, and may lay there undisturbed for six years or more if you don’t have to use it. Our discussion on what to do about that is contained in “All about tyres/original equipment”. Basically, it has missed out on six years of design improvements whilst sleeping in the car boot, or lying in the dealer’s racks waiting for a sale, or in the South Australian’s case, 14 years.

So should tyres have a “Use by Date?” It would appear that provided they have been stored correctly, there is not a problem with tyres encountered in the usual course of trade. Besides, somewhere out of Broken Hill or Wilcannia or somewhere like that, you will be pleased to find that the tyre service has your badly needed tyre, even if it is a bit dusty.

All that applies to tyres also applies to automotive car batteries of course, for all the same reasons, except that a lead acid battery does in fact have a finite life, and has to be stored correctly with its charge maintained until it is sold. The warranty period then kicks in once it is sold.

February 15, 2009 at 4:44 am 3 comments

Online pursuit of tyres is no longer tiresome

Sydney, 29 November 2007 – CarbonBlack TyreXchange (CarbonBlack) today announced the launch of its independent CarbonBlack Tyre Scorecard. The new quarterly report details consumer tyre purchasing habits featuring data gathered at the point-of-sale on http://www.carbonblack.com.au. The CarbonBlack Tyre Scorecard explores pre-purchase consumer triggers for tyre brand choice, brand substitutes, brand preferences and performance feedback. The longitudinal study of consumer behaviours will track the impact of tyre branding activity over time and examine the performance of many existing tyre industry marketing strategies. The October 2007 edition is the first report in a series of high level summaries focused on the automotive industry.

According to CarbonBlack’s founder and managing director, Ms. Jodi Stanton, “Our research indicates that the marketing strategies to tyre consumers undertaken by tyre manufacturers, and distributors vary widely,” Ms Stanton said.

“Obviously some of those strategies are working while others are not – which means marketing expenditure is not being properly targeted. Our research will help direct marketing activities to minimise the risk of missing consumer purchasing triggers, previously difficult to do with more traditional marketing channels such as TV and radio”.

Amongst a wealth of information, the independent report identified:

  • certain brands experienced far greater loyalty than others;
  • consumers increasingly relied on other consumers to influence their purchasing decision;
  • many consumers had reasonably high probabilities of switching brands given the right influence;
  • no single brand produced greater than 60% support when considering purchasing that same brand of tyres again (refer graph 1);
  • marketing campaigns can produce swings of up to 14% in brand awareness with consumers (refer graph 2);
  • the most in-demand tyre requested by purchasers does not even factor on the list of most recommended by tyre dealers (refer graph 3 and 4).

For Stanton the unique aspects of the report will enable the tyre industry to understand what is involved in the purchasing cycle. “Our data is sourced during key stages in the purchasing decision making process when consumer intentions are aligned with their behaviour rather than intention,” she said.

“The report provides ongoing information about the value of brands of tyres in the Australian market that has been collated from information sourced at the time of transaction, from consumer profiling and surveys from consumers actively in the market to purchase tyres.

The results are a fascinating and an extremely valuable representation of the pattern of buying and the actual triggers used by consumers – it is not the theory that a general buying survey might generate,” Ms Stanton explained.

“This will allow tyre industry marketeers to assess the performance of their current messages and also allow them to compare performance against competitors. “

Consumers are growing more sophisticated each year. However, marketing messages tend to be more around umbrella brands and price based promotional campaigns versus specific product differentiation, leaving consumers with little choice but to focus on price.

The first in a series, the CarbonBlack Tyre Scorecard will be followed by reports covering industry issues such as pricing and promotional strategies and channels to market.

The next edition of the Scorecard (January 2008) will be released in February 2008.

November 9, 2007 at 9:15 pm Leave a comment

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