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 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.

Barber Pole Wear

Never heard of it? It’s associated with a vehicle out of alignment, and this article has been prompted by the sight of a short wheelbase trailer’s mad gyrations behind an apparently blissfully unaware Winnebago driver out near Broken Hill recently.

The vehicle involved can be either a car, truck, or trailer. The misalignment is not associated with the “front end” alignment, but the rear.

Suppose a truck is built longer on one side than the other- don’t laugh, it has happened. In one case, the drive axles on one side were located in different holes drilled in the chassis rails on opposite sides of the truck. So two axles of drive wheels were not aligned to the front end of the vehicle – they wanted to drive the truck at a different angle to the direction it was intended to go. So the steering tyres, out-muscled by the 8 drive tyres, had to accommodate their thrust by steering at an angle, in order to get the truck to run straight ahead. The result was that both front tyres wore out, one on the inside, one on the outside rib, very quickly: less than 10000 kilometres, repeatedly. In another case, the jig on which the vehicles were built was out of square by 50 mm.

For a while there was a fashion that the high tensile front axles would be cold-bent to cope with what was thought to be camber wear, when the real problem was further back on the truck. Hopefully, this practice has been diminished by the introduction of laser alignment equipment, which can be used in broad daylight to align a truck accurately. Previously, such alignments had to be done inside in a semi-dark room.

Now align your thoughts to a front wheel drive, where the front axle does all the work of driving and steering, and the rear just trails along for the ride. Experience has shown that for the rear to track correctly, the build tolerances on the relative position of the wheels must be much tighter. If the vehicle “frame” is built out of square, then instead of being a rectangular plot of the wheel positions, you might end up with a parallelogram. Or one wheel position at the rear may have a damaged or misaligned suspension bracket, with the wheel no longer tracking straight ahead. This one wheel will then try to steer the whole car in the direction it wants to go, fighting the other three for control. Of course, it can’t win, but it can make the car steer to one side, which the driver then corrects for at the busy end, and so pursues a somewhat wandering course of constant steering corrections. In an extreme case, the rear wheel can build up so much steering force which the car cannot accommodate, it “lets go”, breaks adhesion, and skips across the road surface whilst still revolving, till it relieves the stresses in the tyre. Then it starts all over again.

This generates a wear pattern called “barber pole wear” after the striped red and white poles outside barbershops. An uneven scallopy wear pattern develops diagonally across the tyre tread, which once seen, is entirely indicative of the whole vehicle tracking out of line.

There are many reasons for this. Let’s go back to the Winnebago. The trailer had a motorbike, and at least four 20-litre fuel cans, all on one side of the trailer. This flattens the springs on that side, which lengthens them, altering the position of the axle on one side. It is no longer at right angles to the direction of travel. The trailer is captive at the towbar, wants to track sideways, so once again, the tyres have to “let go” to get the trailer back behind the campervan. Being relatively light, this was easy, but the gyrations were wonderful to behold.

Scale this up to a 62 tonne B-Double truck, where the axles at the far end of the second trailer are a long way from the steer tyres. If the trailer is loaded off centre, the load has a very high centre of gravity, or the road is highly cambered, then the suspension alignment can be altered in the same way as happened to the Winnebago trailer.
If the unit is known to be habitually operated under these conditions, then the trailer can be set up deliberately out of straight line alignment, so that the whole unit tracks straight.

Trucks that run out of Sydney across the Hay Plains and the Nullarbor to Perth, can attain very high mileages on their trailer tyres, and 200000 km is not unusual. Tyres wear out faster around corners, and there aren’t many of those on that route. Also note these are “trailer tyres”, where the load is a lot less on each tyre than for the steer tyres. The third point is the worn appearance of those high mileage tyres is always very smooth. Tyres that slip in service develop a crepe appearance on the tread face, best seen on a hard worked tractor tyre (which operates at around 15% slip). Close examination of this creped surface can yield a lot of information on whether the vehicle is tracking straight. Here’s what you do- make sure the tread surface is slightly dirty- rub some dust on it. Then stick about four inches (100 mm) of Sellotape strips across the tread, the 2 inch wide stuff is great, press down firmly, lift them off as one piece, and stick them to a clean sheet of paper. Mark the direction of rotation, and the wheel position. Do this for all wheels.
Close examination (a magnifying glass is handy) will show a “grain” present in the imprint of the tread pattern. The direction of the grain shows the direction in which the tyre has wanted to travel. If it’s not straight down the line of the tyre, then the wheel is not aligned.  Steer tyres may show mirror reversed grain divided down the centreline.

Tyres wear faster than they should when they are out of alignment, or the pressure on their tread surface is not evenly distributed across the face of the tyre. The latter can be due to camber problems, or tyre tread- design problems, where the load is not evenly distributed across the tread ribs. Keep in mind that even load distribution is not always possible, because of the shape of the tyre itself, and tyre designers can compensate for this by having the grooves of different depth. The aim is to have all the tyre tread face wear out at the same time.

My first example of “barber pole wear” was a Renault, which the owner had brought it three times to be aligned, getting increasingly upset each time. Spotting this wear pattern, I asked “which wheel had been in the smash?” “That one”, the owner indicated to the tyre with the wear pattern. “They did a real good job on the bodywork, didn’t they, you’d never know” he said, to which I replied “A pity that they didn’t straighten the bent suspension arm as well”.

To make the point, the only way that these problems can be rectified is by having all the wheel positions aligned. For cars, ask for a “four wheel alignment to the thrust line”. Don’t be surprised that it costs more.
For trucks, either buy the truck already laser aligned, or have the whole rig aligned in its working configuration.

Determining the “lead” of your front tyres on a F.W.A. tractor.

Let’s deal with the first question- why do you need to know what the lead is anyway?
Before you start, read the article on ‘Tractor tyres for Front Wheel Assist Tractors‘. This should be ringing warning bells that a little serious study should be undertaken before you need to replace the tyres on your Front Wheel Assist tractor- most frequently the front tyres first.
When the time comes, you might find that these tyres are radials, made in Romania or somewhere (anywhere!), and that you can’t get them, except from the tractor dealer at an exorbitant price. Suddenly your tractor, now 3-5 years old, isn’t such a good acquisition after all.

So some homework is required.

If you fit tyres that don’t match the design engineers’ dimensions, then you run the risk of the tyres failing due to a torque buckle in the sidewall, the transfer case between front and rear drives failing (expensively), or in any case, the tractor chewing up fuel, and getting expensive to run.

There are two ways of checking the lead of the tractor with replacement tyres:

• The book method. If you have the rolling circumference of the front and rear tyres available from printed catalogue information, and are prepared to consult either the tractor handbook for that particular model, or even better, check the specification plate or get under the tractor to check the stamping of the drive ratio on the transfer case, you can do a “book calculation”. Aren’t pocket calculators marvellous! There have been many cases though where the manual says one thing, the transfer case another, so beware. Other forms of the same information are “rolling radius”, or “tyre diameter”, “static loaded radius”, or “revolutions per kilometre”. Note however, that neither “tyre diameter” or “static loaded radius” are fully satisfactory, because they do not allow for the flexing and slip of the tyre as it rolls. They are, as specified, static (stationary) measurements. However, the book method is a way of getting started on the choice of alternative tyres to suit your tractor, and will save you a lot of time in the field.

• The field test method. Our laboratory had a very expensive testing machine installed. On the front of the machine there was a very small plate. You had to lean well forward to read it. It stated “One test is worth a thousand opinions”. The advantage of a field test is that it tests the tractor in the configuration that it is actually going to be used in. The test is carried out on a hard surface. Disengage the front wheel assist and the differential lock to ensure that all wheels are independently free to roll. This may involve keeping it at idle, and check that F.W.A. is not automatically engaged if the engine is turned off. (check the handbook if unsure).

• This method requires a straight, fairly level hard surface up to 100 yards long. A tractor tyre has between 20 and 26 lugs on it, which extend down the sidewall of the tyre. This means that you can divide the circumference of the tyre into around 20-26 segments, so put a splodge of a bright colored paint on the buttress in contact with the ground at the time. (six o’clock position). Hammer a stake into the ground opposite the paint splodges, front and rear, or just lay it on the ground, if you’re sure you won’t trip over them.

• Then tow the tractor forward, with two people alongside, one counting the front revolutions, the other the rear, so you need three people. After ten revolutions of the rear tyres, stop, and lay a stake opposite the splodge of paint, which should be at 6 o’clock. The front tyre splodge won’t be at six o’clock, but probably somewhere up in the air. Count the number of lugs that it has completed in its last partial revolution, keeping in mind the direction of rotation.

Here you have two options. Either place a stake opposite the six o’clock position of the front tyre, and estimate the number of lugs traversed in the last partial revolution (for example 7 lugs out of 24), or better, roll the tractor forward till the splodge is at six o’clock, and lay the stake opposite.
The rolling circumference of the front tyres is given by the distance traversed by the number of revolutions (either partial or complete, the distances are different), and for the rear tyres, the distance traversed divided by ten, so you need at least a 10 metre tape and a couple of markers.

An example, using the whole number of revolutions for the front tyres:

Front tyre

Tyre Size: 13.6- 28
No of revs: 13
Distance b’twn stakes: 50.18 m
Rolling Circ: 3.86 m

Rear tyre

Tyre Size: 23.1-30µ
No of revs: 10
Distance b’twn stakes: 48.57 m
Rolling Circ: 4.857m

You’ve now arrived at the ratio between front and rear tyre rolling circumferences, in this case
4.857 divided by 3.86, equals 1.258
This ratio has to be lower than the transfer case ratio, which can be found on the tractor specification plate, stamped on the casing, or in the handbook. (The latter is the least reliable).

The objective is that the front tyres when driven, have to be rolling FASTER than they want to be when free rolling, and trying to lay down more track than the rear tyres. This generates a “lead”, which makes the tractor easier to drive and steer, it pulls better and is more efficient, particularly so in loose soil. On hard ground (roads), disconnect the front drive to avoid axle windup.

The front tyres are DRIVEN, on average 2% faster than the rears considering the amount of track they lay down. The extra 2% or so is taken up in soil slip, which is what makes it more efficient. In the example above, a transfer case ratio of 1.28 would give a lead of 1.75% (1.28 divided by 1.258, minus 1, multiplied by 100). By the way, the replacement tyres don’t HAVE to be radials, as long as they match the dimensions and the rim widths, they’ll be O.K. Be aware though, that bias ply tyres vary in diameter with pressure, while radials don’t. With bias ply, pressure adjustment can be used to give a final “fine tune” of lead, provided that the usual operating parameters are observed on minimum and maximum pressure, and that you can tolerate the harder ride that might result!

So vent out all that water ballast in your rear tyres. That’s “old technology”, and not applicable to F.W.A. tractors. Reap the benefits at the diesel bowser.

Alignment of Tyres

A vehicle has to track straight on a road that is crowned, or sloped, or flat. The whole vehicle. On some of these huge road trains, their trailers seemingly have a track of their own, whipping from side to side. Yet the modern B-Doubles traveling the major highways, track quite well.

They bear the fruits of a lot of research into vehicle alignment. The whole set-up has been laser aligned to make the trailer track properly. The settings may be different for vehicles that travel the flat roads from the eastern States to W.A. ; or set so the trailer alignment counteracts the high crown of far N.Q. roads.

The Holden Kingswood, or any rear wheel drive car of that vintage, was not as critical in its alignment as the modern front wheel drive. The rear wheels thrust the car forward on the Kingswood, whereas the front wheels drag the car along in the FWD.

There are three major alignment factors- camber, castor, and toe in ( or out). All affect tyre wear and handling. The settings are decided by the car engineers. For example, a Commodore SS has more negative camber than a Commodore Executive, or the tolerances may be set to the maximum on one, the minimum on the other, to improve one aspect of handling.

But there is a fourth setting. The thrust line and its alignment to the drive are more critical in a front wheel drive. If one REAR wheel is out of alignment, it can make the whole car travel crabwise down the road. You see the car drifting off one way or the other, while the unconscious driver is constantly correcting his steering. Once you become aware of this, it’s amazing how many cars you see tracking like that. So if your car has been clipped over one rear wheel, the mountings have been disturbed, or the car repaired after a smash, ask for a “full four wheel alignment to the thrust line.”

If the front tyres on your car (which has had its alignment checked) still wear unevenly on the outside of one front tyre, and the inside of the other, look to the rear end to see what is making it travel crabwise.

Understeer and Oversteer

Most cars have understeer built into them, because it is inherently safer. The car when driven into a corner too fast, will tend to become heavy on the steering, run wide at the front, generate excessive tyre scrub, and thus warn the driver to “back off”, with all these signals being transmitted through the steering.

An oversteering car will tend to have the rear run wide, and the driving technique required to correct it is quite unique. Extreme examples of understeer, are high powered front wheel drive vehicles aka SAAB Viggen “goes like a bullet, handles like a lead tipped arrow”, the reviews said. The old Vee –Dub, and the infamous Chevrolet Corvair. as good examples of oversteerers. Both had a pronounced weight bias to the rear. The Chevvy Corvair resulted in a book called “Unsafe at any Speed” by Ralph Nader, which lambasted the American auto industry for manufacturing such a vehicle.

Vee-Dub pressures were set at up to 30 p.s.i. on the rears, and as low as 17 p.s.i. on the fronts, to help curb the excesses of oversteer. In other words, adjusting tyre pressures can affect the steering characteristics of your car.

So if it’s so desirable, why would you want to change an understeering car. Some drivers prefer that the car be “balanced”, and might even go to the extreme of buying a mid engined car such as a (later model) Toyota MR2, or choose a Alfa Romeo with 50/50 weight distribution, front to back. Using reverse logic to the Vee-Dub, you can make an adjustment to your tyre pressures to reduce the understeer on your family sedan, or small F.W.D. An extra 4 p.s.i. (30 kPa) in the front tyres, and lower 4 p.s.i. in the rear tyres, will change the steering characteristics of your car. Of course, the usual disclaimers apply. You must always have enough air in the tyres to carry the load, so don’t do it when the car is fully laden for your vacation.

Other performance vehicle makers will tailor the handling by having a wider tyre on the rear, maybe even a lower profile, so that the rear will always out corner the front tyres at the same slip angle, and won’t overtake the front of the car in a spin, which is very embarrassing, even dangerous for the driver. Yet they only provide one spare wheel!

Alignment – Tell me a story

Your worn tyres will tell an experienced tyre man a great deal about the mechanical condition of your car, and the way you drive it.

Tell-tales on a rear wheel drive are rear tyres worn in the crown (hard driving), rear tyres worn on the inside only (I.R.S. camber /load relationship), and tyres worn scored or smooth-surfaced (jack rabbit starts or not).

Front wheel tyres worn excessively on the shoulders show up misalignment, fast cornering, and underinflation. That’s just some of them.

Front wheel drive cars are different. The front tyres can wear nearly twice as fast as the rears, and can show wear in the crown, and excess wear on the shoulders, at the same time, for all the reasons listed above.

Yet the salesman will spend much more time trying to sell you the flavour of the month, and then recommend that you have a wheel alignment after new tyres are fitted.

What are the benefits? After all, alignment can cost quite a bit, and it might seem hard to justify. For the dealer, the installation is a big outlay in both equipment and training for the operator.

However, tyres are an expensive item, so here are some of the benefits:

• The car is easier to drive and steer, so long trips are less tiring.
• Tyre life is increased, particularly if the alignment on the previous set was out of whack
• Restoration of the steering angles designed into the car will make it handle the way the designer intended.
• You’ll get your money back in extended tread life, provided of course that you don’t indulge in the improved handling and cornering that result.
• Adjustment to your suspension camber can be made to suit the way you use your car. For example, suspension can be adjusted if the car has a high negative camber for fast cornering, but is used mainly on freeways. Aftermarket kits are readily available to permit these changes.
• If you’ve had a bingle, make sure that your car is completely aligned before you sign the release form from the panel works.
• If you have kerbed your front wheels badly, it will pay to have them checked.
• After any front end work on steering or drive components, alignment is highly desirable.
• Ask the tyre salesman before he launches into his spiel, to assess the wear pattern on your tyres, and advise him how you actually use the car, before he makes a recommendation on the best tyre for YOU.

See also the following article on misalignment to the thrust line of the vehicle, particularly on front wheel drives.

Tyre Noise

Some of the tyre characteristics that intrude into the passenger cabin of the modern car are tyre harshness, whine, slap, and sizzle.

Harshness can be felt as a vibration or buzzing transmitted through the steel box that is the car, that makes the radio grille buzz, the cigarette lighter tray get excited, and generally is intrusive.

Whine is not “Are we there yet?, but a noise which goes up the scale as the speed rises and falls. Lug tyres on four wheel drives are prone to it. With some, you don’t need a speedo to tell you how fast you’re going.

Slap is the noise generated when the tyre is running over the joins in a concrete road.

The last one, sizzle, is the most interesting. It can be heard on a smooth wet road, or on a hot dry smooth road. It is generated by a tread pattern that has been cut up into “a lot” of small discrete tread blocks, or ribs which have lots of slots cut into them. These slots are called “sipes”, and in many cases, are placed profusely in the centre of a rib around the tyre. This is called a “highly siped pattern”. In most cases, the sipe depth is not as deep as the tread groove which separates the tread into blocks or ribs. When the tyre is half worn or thereabouts, in many cases, they disappear, so their effect on wet road holding can be described as transitory.

Sizzle can be quite annoying. Fortunately, most roads in Australia are laid with sharp screenings pressed into the asphalt, which generates another tyre noise called “coarse chip roar”, which everyone has experienced at some time. That can really make things buzz inside the car.

One particular tyre maker once released a very highly siped pattern with 3200 sipes, which sizzled. It became the subject of some criticism, which was quelled by an advertising campaign that promoted it as “ the sound of safety”. All those little knife edges wiping the road dry when it was raining were working for your safety. On a hot smooth road, bad luck!