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.

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.

Goodyear Wingfoot teams with Aussie Lightfoots

Helen and John Taylor, an Australian couple who have made a speciality of setting records for low fuel consumption in the USA, have done it again.

Converting their miles per American gallon to litres per hundred kilometres yields an astonishing 4.155 litres /100 km in their 2009 Volkswagen Jetta diesel.
This time they were riding on Goodyear Fuel Max tyres, and improved on their 2008 figure by a further 15.4%!

This consumption is more fuel-efficient than the most popular hybrid, and shows what can be done with modern diesel technology, careful preparation and fuel saving driving techniques.

Follow this link to learn more.

So how do they do it? Tyres obviously play a part, since Goodyear sponsored their 9000 mile circuit of the States. We are constantly told to maintain high air pressures if fuel savings are desired, but what are the limits? A tyre usually absorbs around 2 KW just rolling around under load at 120 km/h.

The safe maximum pressure of a tyre is shown on the sidewall, and for a passenger tyre is in the 36 (Standard Load)- 42 (Extra Load) p.s.i. range. It will not burst at 43 p.s.i., but a maximum is specified to maintain a margin of safety for tyre abuse such as potholes and rough edges. So economy drivers go to the limit, or beyond. A tyre with 15 p.s.i. pressure pulls nearly twice the rolling resistance as the same tyre at 33 p.s.i. at 120 km/h, the higher pressure giving a fuel consumption improvement of about 4%. Steel belt radials have the lowest rolling resistance, too.

Staying with tyre design, a narrow tread width, shallow tread pattern, and a rounded tread arc radius all contribute to lower rolling resistance, and with specially compounded tread rubber it is possible to design a tyre to maximise the reduction in a tyre’s contribution to fuel consumption.

Preparation of the vehicle using low friction lubricants, a well run-in engine, diesel fuel designed to give “more bang for the buck”, and other tricks of the trade are also used, such as refuelling at low ambient temperatures, like the middle of the night.

But driver’s skills are required to get good figures. Feather-footing, low top speeds, shift points carefully calibrated, travelling when wind speeds are low, smooth car surface with no unnecessary projections, climbing hills carefully (just making it over the top), and no air-conditioning are techniques used. Depending on the rules of the contest, in most cases coasting downhill, and drafting, is prohibited. In certified fuel economy runs conducted in Australia, an independent observer travels in the car to prevent this.

Want to know more on the tyre angle? In our All About Tyres section you will find Green Tyres are Black, David’s ten tyre tips, and Exploding Cylinders which will expand on rolling resistance and fuel consumption.

Why CarbonBlack?

Our Website is named CarbonBlack- because that’s what tyres are made of – right?

Well, partly – about 35% of a tyre is carbon black.
So what is it? And where does it come from?

As with most things these days “Oil” is the answer, which is one of the reasons why tyres cost so much.

Carbon black USED to be made from burning natural gas in insufficient air, and collecting the smoke that resulted, rich in carbon, on cooled metal surfaces. This was sometimes called “lampblack’, or later “channel black”. The pollution it caused was indescribable, let alone the waste that escaped to the atmosphere.

So another process took over in the early 1950s, called “furnace black”. Oil was burned inside a furnace in insufficient air, and the resulting carbon collected at the outlet. Dependent on the type of oil burned, the design of the furnace, the operating temperature, the flow rates, nozzle design, and any number of variations, it was quickly discovered that the actual properties of the carbon black (still just carbon remember) could be varied.

A whole new family of carbon blacks resulted, from the smallest particle size, intensely black as used in printing inks, to the larger and softer grades used in say motor tubes, which had quite a grey colour, and all the grades in between.

But wait- there’s more, as the Demtel man used to say.

The actual surface of each carbon particle could also be varied, to be extremely absorptive or low absorption. This structure varied the way that the carbon molecules could be intimately mixed into the long chain rubber molecules, which affected the degree of reinforcement imparted to the rubber by the carbon black. This then had a direct affect on the physical properties imparted to the rubber by mixing it with carbon black, such as wear, cut resistance, tensile strength, stiffness (modulus), elasticity, heat build-up under flexing, and a host of other properties.

So the fast developing science of carbon black became dominant in the development of rubber compounds. Without carbon black, tyres would be slippery in the wet, would wear out very quickly (particularly when hot), and generally would not be suitable for today’s automotive uses. That’s just the tread. Other blacks were designed for use in the casing, in the tubeless liner, bead compounds, bead stiffeners, and the many other applications used in a tyre.

The name of our web site pays homage to its importance to the rubber industry.

Terrible stuff to get out of your skin though. I couldn’t wear a white shirt for years!

If tyres burn, why don’t we set them alight and save the planet?

Riots in the streets are nearly always accompanied by stacks of burning tyres defining the no-go zone. They burn very well, although smokily. Once started, they’re almost impossible to put out.

So why aren’t they used more widely as fuel if they burn so well. After all, there is a millions of tyres discarded worldwide every year. They are no good for landfill, because they don’t decompose, and are hard to keep below the surface. In fact, I know of a pile of over 200 million tyres outside L.A. waiting for someone to devise a use for them.

Furnaces to burn them have been developed, and the resulting heat used to raise steam, or for central heating. These take either whole tyres, or shredded tyres, use a conveyor feed system to load the furnace, but somehow haven’t been widely adopted. Someone has to load the conveyor, too!

The reason for non-adoption is possibly “acid rain”. When rubber is vulcanised, it is combined with sulphur. This process cross links the rubber molecules, and converts the rubber material into a stable, three dimensional lattice, which is elastic. The level of sulphur is generally 1 to 2 percent. This level of sulphur is around the same as for high sulphur coal. When burnt, (oxidisation) it becomes sulphur dioxide, and other oxides such as sulphur tri-oxide, dependent on the air/fuel mix. Burn coal, you get carbon dioxide, burn tyres you get sulphur dioxide. High sulphur coals are very much out of favour.

In the atmosphere, these oxides of sulphur combine with water to form sulphuric and sulphurous  acid, which pollutes the air, kills vegetation and our forests which are the lungs of the world.

So a great deal of research into the design of the furnace to minimise these effects and scrub the exhaust gases clean of smoke and pollutants is required, which makes the furnace more expensive.

Then there’s the costs of collecting the old tyres, sorting , classifying, shredding, and the costs of disposal of the ash that results from the burning, though the steel content can be recovered as slag from the furnace grate. However, there awaits big rewards for the designer of a furnace that will be easily portable, has a captive market for its product (heat), and a ready supply of worn out tyres available at preferably no cost.

Google’s new algorithms – patience required or we pack our bags for Bing

SEO gurus and webmasters have watched over the last few weeks as Google has been changing its SERP rankings. From what we can tell so far, there seems yet to be clarity on the changes. To the frustration of all of us, Google does not announce their algorithm updates, and we continue to test results and frequent blogs and forums to gain any further insight. But many gurus suggest Google is experimenting with trust and authority in their algorithms.

“We have well established sites being outranked by new sites and by sites with very few backlinks. Also by sites using black hat techniques and unfortunately we see some established and often very trustworthy white hat websites simply disappearing from the rankings altogether. At the same time we have literally day old Craigslist posts ranking in the top results. Some .edu and .gov sites have flown to the top while others have plummeted.” (SiteProNews)

Patience required or we’ll pack our bags for Bing.

The CarbonBlack SEO team will keep you updated in our blog.

Green revolution in auto-industry

Firestone Autocare shops in two American States are test marketing the use of twice-refined, used motor oil during routine car servicing.

The mind boggles that sufficient oil is available for collection, re-refining, and distribution to justify the program.

However, economics will determine whether the program is ultimately successful or not.

Recycling used oil uses 85% less energy than processing oil from new, Firestone executives claim. Many parallels to recycling tyres by retreading them can be drawn.

Good on them for having a go.

If you want to know more, go to http://motorage.search-autoparts.article/articleDetail.jsp?id=950056

Tyre Tread Compounds

There’s a great deal of confusion amongst car enthusiasts, particularly the “rubber burners”, on tyre tread compounds and their make-up. One enthusiast on a car blog announced that tyres weren’t made from rubber at all, but from oil. You know what- he was mostly right!

Oils ain’t oils, and rubber ain’t rubber any more.

Tyres contain 3 or 4 different rubbery materials. One is natural rubber; which is the juice of a tree, which is coagulated using acetic acid, smoked and dried. The others are all made from oil, and are called “polymers”- another term is “long chain macromolecules” but don’t worry too much about that. It is now possible to make “natural rubber’ from oil too, but it’s cheaper to let the tree do it.

These various rubbers can be mixed together in different ratios in giant blenders to make a compound. At the same time, other important ingredients are added to make the resultant product tougher and stronger. A typical tyre compound may contain 10- 14 ingredients, all added for a specific reason. The most important of these is carbon black, of which there are many types.

A tyre typically has 7 to 11 compounds, each doing a specific job, be it encasing the bead wires, keeping the air in a tubeless tyre, flexing the sidewall, sticking the layers of nylon or polyester together, and so on. But there is only one compound that hits the road where it all happens, and that’s the tread compound.

This is basically the only criterion on which the motorist can judge the performance of the tyre, so it receives the most comment from car enthusiasts. The tyre engineer and chemist can vary the compound formula to maximise/minimise any tyre characteristic that he requires.

A typical passenger tyre tread compound contains as the base polymer styrene-butadiene copolymer, around 35% carbon black to reinforce it, and maybe some silica. These increase the abrasion resistance, tear strength, and cut resistance. Without them, the tyre would go gooey, and wear out very rapidly. Remember those old crepe rubber soled shoes?

Vulcanisation chemicals such as sulphur, zinc oxide, stearic acid, and accelerators make up 3-5%; antioxidants and antiozidants to stop it perishing or cracking, processing aids such as oil, resins, tackifiers to aid in the lay-up of the assembly are all incorporated.

Some tyres have two tread compounds- either side by side (very rare), or a cooler running undertread compound under a harder, hotter running cap stock. Most, however, only have one compound in the tread area.

The rubber used in tyres is normally a copolymer ( mixed and then polymerised together) of 23% styrene, and 77% butadiene. However, this ratio is not set in concrete, and specialty rubbers of different proportions of these two refinery products can be made. For example, “cling rubber”, which was widely touted for its improved wet grip, is 40% styrene, 60% butadiene. The resulting rubber ran hotter, and wore out quickly under Australian conditions. A 90% styrene, 10% butadiene rubber is used to make floor tiles, not car tyres.

Another rubber developed for use in tyres is polybutadiene. Butadiene is the most common feedstock from a refinery. However the resultant polymer suffers one big disadvantage- its wet grip is poor. Its big advantages are however, that it stands up to extreme abrasion much better than other rubbers, and runs cooler. Back in the days when the Armstrong 500 Miler was run at Phillip Island on standard tyres and rims, and the track was not a smooth hot mix like it is today, Harry Firth won the race by changing only one tyre, whilst everyone else changed at least twelve on the very abrasive track. But he lost 3 seconds a lap, because down on the ocean side, the tyres wouldn’t grip to racing levels. The tyres were made from a high proportion of polybutadiene in the tread, specially airfreighted out for the race.

We’re not as skilful as Harry Firth was then, and the Australian motorist puts “grip in the wet” as the top desirable characteristic from his tyres, so its use is now mainly confined to truck tyres in blends with natural rubber, where heat is the main enemy of tyre performance.

So ultimately, it’s the “grip” of the tread compound that drives, steers, and brakes the car, through the contact patch, around the area of a size 12 shoe. It does this by slipping! Sliding generates friction, and this causes things to happen. All tyres slip, particularly driven and steering tyres, which is why they wear out. No friction- no progress. Try driving and steering on black ice sometime to see what I mean.

“Rubber burners” overlay this with “sticky friction” by heating the tread surface till it starts to revert- goes gooey. Lots of smoke! On top of this, tyres generate heat internally from the stresses generated by flexing (the hysteresis loop). As the rubber warms up, the rubber changes its grip characteristics, provided that the compound hasn’t degraded to the gooey stage (“goes off”). This occurs generally in the thickest part of the tyre under the greatest load, like the outside shoulder of a tyre being driven on a banked circuit. That’s why you see tyre technicians who are evaluating tyres, drive a thermocouple needle into the shoulder of the tyre tread- the thickest part. The electric blankets on the wheels ready for a change onto a race car are there for the same reason- so that the car will handle similarly to the old, warmed up tyres.

The position of the white stripes in the tread grooves of the Formula 1 cars indicates the type of compound used in the tread. The tread grooves are there to slow the cars down, even when the road is dry. Race team managers under F1 Rules have to use at least two types of tyre during the course of the race. This adds another source of tactical variation for managers to consider, as though they haven’t got enough on their plate. But the race result may have been decided in a tyre development laboratory in Kobe or Luxemburg or wherever, since so much data has been accumulated on the vagaries of each circuit, and the tyre compound that performs best on that circuit.

It’s almost time for the Melbourne Grand Prix- so enjoy your viewing

CarbonBlack in the AFR – Mar 3 2009

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 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.