eTyreLife and Tyre Management
Unless you want to pick tyres for your vehicles based on gut feelings, intuition or data gathered by your peers, a good record keeping system to track tyre performance and costs in your fleet is vital to making wise tyre decisions. And whether your records are on paper or on high-powered tyre-specific software – such as eTyreLife – is up to you.
A good recordkeeping system will store all the data you need to determine the actual costs associated with the tyres in your fleet. While most of the initial costs in a tyre-tracking program are obvious — new tyres, casings and retreads and repair materials — there are other related costs that must be accounted for. Those include the labor associated with tyre management and repairs, tyre replacement costs and the cost of downtime associated with tyre issues that occur.
Paper Versus Computer Tracking
There is nothing wrong with keeping paper records of when tyres were installed on a vehicle, when they were removed and associated tyre costs. If you manage a handful of vehicles, paper records might work. But when you’re managing a fleet and the type of vehicles range from local or regional delivery to long-haul, the complexity of keeping records ‘the old-fashioned way’ becomes next to impossible.
One should be proficient in spreadsheet analysis that will record all the data and make the calculations you need to determine the total costs and, even more important, the cost per KM of every tyre in your fleet.
If developing a very complex spreadsheet is not in your skill set, you may wish to invest in software to help your cause. There are few software packages available in the market, some better than others. BhoktuM management offers eTyreLife that can aid in the quest for better information.
Information-Based Decision Making
Good tyre-tracking software allows fleet managers to document tyre related information (mileage and cost) and calculate cost-per-KM in several ways. With eTyreLife, information is entered for each vehicle, with mileage recorded when new tyres (or retreads or regrooved) are installed. Down the road, costs associated with these tyres are also documented - treadwear is measured and entered into the software at every frequent inspection and as well when they have been removed from service.
Although cost-per-KM can be calculated and shown graphically at any time by brand or tyre type, it is best to wait until tyres are at least 50 percent worn to draw any preliminary conclusions.
Better yet, wait until a significant number of tyres are out-of-service before using the data to help make major purchase decisions. This gives you a more accurate picture of what’s happening with your costs.
Once tyres are out of service, data gathering continue through scrap tyre analysis. This type of data can be captured by eTyreLife and summarized results can be shown with various charts and graphs.
Knowing why tyres are removed, the age and number of retreads you are getting on casings, indicates whether your tyres were properly maintained. For example, if tyres are wearing out due to scrubbing or curb damage, you may wish to compare different types of tyres and use eTyreLife to document whether you’ve found a better solution.
Unlike some Tyre-tracking software's which are just intended to track few tyres of your fleet and ask you to take decisions based on samples, eTyreLife is designed to track every Tyre in your fleet and add value. It can give robust analysis to help you make well informed decisions, including Tyre requirement estimations and budget estimations for coming months and years in your fleet.
Predicting Tyre Costs Though Information
Keeping good records and possessing data that predicts tyre wear can help lower fleet costs. Knowing which tyres are most cost effective on a fleet’s trucks can assist future tyre purchase decisions.
What’s more, knowing the wear rates of tyres allows you to anticipate peaks and valleys in the replacement tyre purchase cycle. This could help with budget planning in the months and years ahead.
Putting Data To Work
Tyre performance between different company locations or terminals can be tracked in the same way as performance on different fleet vehicles.
eTyreLife software allows fleets to pinpoint problem areas or establish best practices based on outstanding performance in one or more locations. Information is power, and once you have data compiled, you can put it to work for you to make intelligent tyre decisions.
A well-run tyre program transcends buying quality tyres. Tyres should be viewed as a system. It’s tread and compounding, the casing, maintenance practices and tracking to determine what works best.
When your job is to stay profitable through low cost-per-KM and tyres are one of your highest operating costs, it’s imperative to track your numbers. It’s the only way to a solid bottom line.
Fuel economics and Tyres
Though there are a number of factors that contribute to the amount of fuel used by a vehicle, the main parameters are:
- Vehicle weight,
- Aerodynamic drag,
- Mechanical losses,
- Driving style and
- Rolling resistance.
Although Tyres are just one of these factors, they can affect up to 1/3 of the vehicle's total fuel consumption.
Contribution of tyres to the total energy required to move a vehicle down the road depends upon effects of many outside factors, which include:
Aerodynamics and Speed
Vehicle's aerodynamics and travelling speed have extremely large impact on how much fuel is consumed. The force created by aerodynamic drag of a vehicle goes up exponentially with the speed of the vehicle. Tyre rolling resistance increases linearly with speed. But tyres are a proportionally smaller percentage of the total drag on a vehicle as the speed increases.
Vehicle ConfigurationTyre Inflation
On a typical 40 ton, 5 axle truck, each axle contributes to a portion of the total vehicle tyre rolling resistance. Drive and trailer axles combined contribute about 83% of the total tyre rolling resistance.
To minimise the vehicle's fuel consumption, it is recommended to equip all axles with low rolling resistance, fuel efficient tyres.
Tyre rolling resistance is heavily dependent on inflation pressure. 1 bar(14.5 psi) deviation from the nominal inflation pressure could lead to a 5% difference in rolling resistance, which may result in significant fuel cost increase.
For optimum rolling resistance, it's important to have tyres inflated correctly, as recommended for the respective axle loads. Also, under inflation may have negative effects on tyre durability and can cause failure.
Incorrect axle alignment drastically influences rolling resistance, increasing fuel consumption and causing quick tyre wear.
If axles on a truck are not properly aligned, drag increases and the tyre wear-out much faster. This means, more fuel used and quick tyre wear.
Driving habits or style of the vehicle driver can have very large influence on the amount of fuel consumed. Aggressive driving can wipe out many of the gains obtained from investments in fuel-efficient tyres and engines, aerodynamic devices or synthetic lubricants.
With today's technology, it is possible to accurately measure the amount of fuel a vehicle uses over a period of time allowing for programs to be set up to reward drivers for good fuel efficiency.
Tyre Rolling Resistance
Apart from the recommended use of specific "fuel efficient" tyres, below are few general comments concerning factors affecting tyre rolling resistance:
- Rib type tyres are better with regard to rolling resistance than block type tyres, this is mainly due to less movement of the tread in the contact patch area.
- Low aspect ratio tyres are stiffer, allowing for less flexing under load, thus they typically have lower rolling resistance compared to high aspect ratio tyres.
- Worn tyres have less rolling resistance than new tyres - as a truck tyre wears down, the tread pattern stiffens, which leads to less flexing/deformation in the tread area.
The use of fuel efficient tyres on all axle positions can make a significant difference in fuel consumption, a reduction of 10% of rolling resistance on a complete vehicle results in approximately 3% reduced fuel consumption (approx 0.9 litres/100 km on a vehicle which consumes 30 litres/100 km).
Ambient air temperature, weather conditions, road surfaces (sand, gravel, asphalt, concrete) and terrain (flat, hilly or mountainous) are environmental factors that are impossible to control but have a direct effect on fuel consumption.
A high grading in fuel efficiency represents less rolling resistance and directly impacts on fuel consumption and the environment. With lower rolling resistance a tyre requires less energy so less fuel is used and, in turn less CO2is emitted. A win-win situation.
TYRE, THE PNEUMATIC TYRE
It has been said that the invention of the pneumatic tyre was one of the greatest developments of modern times. Without it, the automobile and truck could not have advanced to become the vehicles we have today.
The name "tyre" was derived from the function of tying together the spokes of early day wagon wheels with a wooden "tyre". Later, leather, then a metal band, was put on for increased durability. As uses for rubber were developed, a solid rubber "tyre" was put around the wooden one for reduced noise and comfort. Later developments of a hollow belt filled with air gave birth to a pneumatic "tyer" or tyre, as we know it today. During World War II, when a grave shortage of rubber coincided with an exceptional demand for tyres, various inventions sought to replace the pneumatic tyre. Among these were cushion tyres, spring wheels and pneumatic hubs, but none of them were successful.
TRUCK TYRE TYPES: BIAS AND RADIAL
The bias-ply truck tyre is made up of a number of textile cords (rayon, nylon, polyester, etc.) set on a bias (at an angle) going from bead to bead, with each layer forming a cris-cross pattern with those above and below it. Depending on the tensile strength of the cord used and the required size of the tyre, there could be from six to 20 plies in a bias-ply casing. The number of plies must be increased to improve the carrying capacity of the tyre. There are no steel belts to stabilise the tread in a bias-ply tyre. A big disadvantage in using textile cords is that a large number of cords are needed to give the tyre its required strength. This gives the tyre a thick, rigid casing.
Because the strands of fabric in the sidewall extend through the tread, the tread and sidewalls work as if they are one unit. As the sidewall flexes, the tread and contact patch distort, resulting in abrasive forces similar to a pencil eraser.
Textile is a poor heat conductor and does not dissipate heat very quickly. In textile cords which make up bias-ply tyres, the heat build-up tends to pocket in certain areas of the tyre, especially the shoulder and bead area, which are flex points. The excess heat generation prematurely ages the components and shortens the life of the tyre.
Another factor resulting from heat generation is that textile cords stretch during their life. Therefore, the casing grows and this makes it difficult to obtain a perfect match of new, worn and retreaded tyres. The tensile strength of the textile cords is not as high as that of steel cords.
The number of cross plies in a bias-ply tyre tends to stiffen its walls, preventing sufficient flex under heavy load. By having such a thick casing, there is greater heat build-up which results in more energy being absorbed by the tyre. The plies in the bias tyres stretch and do not return to their original cold strength.
In summary, the main disadvantages of the bias-ply tyre are:
- Tread distortion causing low mileage and poor road grip
- Heat build-up and retention causing breakdown of textile cords
- Casing growth and loss of strength causing poor retreadability and difficulty in matching tyres.
- Textile cords are less able to prevent punctures resulting in air loss and an increased likelihood of downtime.
Bias-ply construction has been in use for about 80 years and has reached the ultimate in its development. Today, less than 1% of the total replacement truck tyre market in Australia and New Zealand is bias.
Michelin introduced the radial truck tyre in 1952. This new concept in truck tyre technology used steel as a casing cord, with belts placed circumferentially under the tread.
The radial was introduced to meet modern transport needs (safe and efficient operation), minimise downtime and reduce maintenance.
The cords in the radial casing are wrapped at a ninety-degree angle to the bead wires, a design feature that makes the tyre's walls extremely flexible. These supple walls "give" under load, absorbing unevenness in the road surface. The radial, therefore, introduced a new era in driving comfort.
Another radial innovation is the belt around the casing that braces and stabilises the tread, improving contact between the vehicle and the road, reducing unwanted movement in the tread-road contact area.
The steel belt tread area and the radial sidewalls work as if the two parts are independent of each other, producing multiple advantages and benefits.
ADVANTAGES OF RADIAL TYRES
Because of the low distortion and more uniform contact stress distribution of the tread area, radials reduce the rate-of-wear per mm of rubber. This can yield a considerable increase in tyre mileage.
Greater road grip
Reduced distortion of the tyre in the contact area and the use of more efficient tread designs allow better traction.
Less Heat Build-Up
The separation of the functions of the tread from that of the casing in the radial tyre allows for less heat build-up than in bias-ply tyres. Thus, the tyre is cooler running, extending the life of the casing (more kilometres) and saving fuel.
A radial tyre saves fuel as a result of the actions of radial construction and a reduction in heat build-up. The tyre runs cooler. Also, tread squirming and shuffling is greatly reduced and the resistance to tyre rotation is decreased. Less power is needed to propel the vehicle forward and less energy is wasted merely generating heat within the tyre. The cooler running radial tyre saves fuel and conserves energy.
The steel casing does not grow or stretch as fabric does and, therefore, it is possible for a new radial tyre to be used with a retread, size for size, provided they are of similar tread depth.
The radial can be retreaded with any type of system. If good quality workmanship and materials are used in the retreading process, similar life expectancy to the new tyre can be realised and all the advantages of road grip, less heat build-up, fuel savings, fewer flats etc. can be expected from the retreaded casing. Retread acceptance level is also a major factor in generating the lowest cost per kilometre.
More flexible casing
The greater flexibility of the casing offers four advantages:
- Greater comfort to the driver
- Greater protection to the payload, especially fragile equipment or goods
- Greater protection to the vehicle with less vehicle body repairs or spring breakage
- Easier mounting
Fewer punctures (Reduction in Downtime)
The use of steel-protector plies in the crown helps resist damage caused by road hazards.
Ease of Repair
Repairs can be done more effectively on radial-ply tyres than with bias-ply tyres. If damaged, the injury affects only a local area and, provided the proper radial-ply materials are used, the tyre can often be repaired and put back into service. Hidden damage is easier to determine than with bias-ply tyres due to fewer plies camouflaging the damage. Larger size damages can more often be repaired in radials than in bias.
The possibility of better, more advanced tread designs on a radial casing also allows the use of a more efficient quieter rolling tyre when compared to bias-ply.
With the tread de-coupled from the sidewall, a more uniform contact stress pattern allows the use of more advanced tread designs offering lower rolling noise.
The most critical factor in tyre maintenance is proper inflation. No tyre or tube is completely impervious to loss of air pressure. To avoid the hazards of under-inflation, lost air must be promptly replaced.
To determine the proper inflation pressure, all trucks should be weighed. Encourage truck owners to weigh their vehicles, fully loaded, on a scale.
Each axle (or axle group), front and rear, and trailer must be weighed separately. Actual gross axle weights should be compared with the manufacturer's tyre data book to determine the inflation pressure required. The load carried by each individual front axle tyre should be noted.
If the maximum load-carrying capacity of the tyre is below the actual scale weight, greater carrying-capacity tyres must be used, either a higher load index (load range or ply rating) or a larger tyre size.
Many of today's tyre problems are caused by insufficient or careless attention to tyre pressures. It is the air in the tyre which supports the load. If we have incorrect pressures, such as over-inflation, the tyre will be more susceptible to damage in the form of shocks and rapid tread wear. The opposite condition is referred to as under-inflation. Under-inflation will increase the deflection of the sidewalls. The effect of over-flexing and the generation of too much heat will cause carcass fatigue and deterioration.
Below is a chart illustrating the effects of variance in tyre pressure on the life of the tyre:
RADIAL TYRE COMPONENTS
The following is a diagram of a cross section of a tubeless radial truck tyre.
Casing Ply Steel cords comprise the body of the tyre. They must have sufficient tensile strength to hold the air pressure required by design and application. All driving, braking and steering forces are transmitted between the wheel and the tread of the tyre by the casing ply. Cushion Rubber This rubber is used as the bonding agent between the various components within the tyre. The thickness in the crown also helps to absorb shock. Tread Pattern The rubber on the outer circumference of the tyre in contact with the road surface. It usually contains a pattern or design made of ribs, lugs, gr sipes for road grip. It is compounded for resistance to wear and must provide acceptable anti-skid properties. Shoulder The section of tyre which joins the outer edges of the tread to the sidewall. It affects cornering and is compounded to give added resistance to wear from use and atmospheric conditions. Crown Comprised of steel plies laid at an angle on top of the casing ply like a belt. Its function is to stabilise the tread area of the tyre and minimise tread distortion. Sidewall The portion of the tyre between the shoulder and the bead. The sidewall rubber must be compounded to withstand constant flexing of the casing. The sidewall rubber protects the casing ply from abrasions and atmospheric conditions, but does not actually strengthen the tyre. The suppleness of the sidewall makes a major contribution to the smoothness of the ride. Inner Liner A layer of butyl rubber bonded to the inside of a casing to improve air retention, thus making it a tubeless tyre. Bead Area The portion of the tyre that serves as an anchor between the carcass of the tyre and the rim flange. Also provides greater lateral stability Bead protector ply A layer of cord covering the bead wires in some tyres for protection against chafing and to reinforce the bead area and lower sidewall Bead Heel The portion of the bead which sits against the rim flange . Bead Sole The portion of the bead that sits on the tapered rim seat. Bead Toe The front portion of the bead sole which is an integral part of the bead. Bead Core Steel wires wound in varying numbers to form a hoop placed circumferentially in the bead area of the tyre. Their function is to hold the tyre on the rim and to form an anchor on which the casing ply or plies are wrapped.
TUBELESS VS TUBE-TYPE TYRES
As radial tyres have replaced bias tyres in the trucking industry because of performance, tubeless tyres have replaced tube-type tyres due to their performance.
The following diagram shows the increased number of components associated with tube-type tyres.
Summary Of Tubeless Advantages
- Ease of Mounting - fewer parts… no flap, tube, lock rings. Saves on labour costs.
- Better Handling - equivalent size tubeless tyres have a lower sidewall height providing greater responsiveness.
- Cooler Running/Added Fuel Savings - less internal friction without tube and flap.
- Reduction of Run Flats - the butyl liner clings to penetrating objects, thus, slowing air loss.
- Reduction of parts inventory (rims) reducing risks of mismatching rim parts - Safer handling when mounting.
- Lower Weight - tubeless wheel saves weight allowing more payload. As an example:
COMPONENT WEIGHT IN KG COMPONENT WEIGHT IN KG 10.00R20 XZE 49.5 11R22.5 XZE2 56.5 FLAP 4 TUBE 2 WHEEL* 45 WHEEL* 38 TOTAL ASSY 100.5 TOTAL ASSY 94.5
- Typical weight for 7.5x20 multi-piece wheel and 7.5x22.5" tubeless steel wheel.
- Longer Casing Life - casing life is extended due to the lower operating temperatures.
Radial tyres should be rotated only when necessary. If the tyres are wearing evenly, there is no need to rotate. If irregular wear becomes apparent or if the wear rate on the tyres is perceptibly uneven, then the source of this wear should be corrected and the tyres should be rotated in such a manner to alleviate the problem.
On trucks, particularly with duals, a change of tyre position can frequently avoid low tyre mileage or prolong casing life. Rotation procedures, such as those recommended by vehicle manufacturers, may be followed.
When rotating tyres, the following points should be taken into consideration.
- The load carried by a particular tyre in a particular position. The inside tyre of a dual mounting carries more load than the outside tyre on the same axle.
- Adjacent dual tyres should not differ more than 4 mm in diameter (2 mm in tread wear).
- Curbing on dual applications damages tyre sidewalls. If so, rotate the wheel and tyre to the inner wheel position.
- Often it is beneficial to rotate the tyres so that irregularly worn tyres are moved to a position where they are turning in a direction opposite to the original position.
- THERE IS NO RESTRICTION PREVENTING DIAGONAL ROTATION.