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7. Wide-Based and Low Rolling Resistance Tires

Wide-Based and Low Rolling Resistance Tires

With practically no additional costs, single wide-base tires and low-rolling resistance tires offer highly attractive measures for reducing GHG emissions and increasing fuel efficiency.

Important obstacles stand against the adoption of innovative technologies, of which one of the most important is the lack of practical information coming from independent sources. The objective of these fact sheets is to inform those in the trucking industry about new and emerging advanced technologies that have been tested through the Energotest program (run by FPInnovations), which can help increase fuel efficiency and, at the same time, reduce the environmental impact of freight transportation in Canada.

Description

Rolling resistance is the drag force that is created when tires roll along the road, and can consume as much as 70% of engine power at low speeds and as much as 40% at high speeds. Each 3% decrease in rolling resistance could improve fuel efficiency by as much as 1%. For tires, an estimated 60% of the rolling resistance is created by the tread and 40% by the casing.

Wide-Base Tires

One way to improve efficiency would be to use single wide-base radial tires to replace conventional dual tires. This approach offers two key advantages: fuel and weight savings. In addition, a single wide-base tire and rim costs less to purchase than a set of dual tires and rims. Savings in the range of $100 to $150 per set (tire and rim) can be expected.

According to manufacturers, the operational fuel savings from using these tires is at least 4%. Track tests performed by FPInnovations during the Energotest™ campaign, at a constant speed of 100 km/h, resulted in reduced fuel consumption by 9.7% compared with conventional dual tires. Because trucks do not operate 100% of the time at full highway speeds, results during operations should be lower. For example, an operational observation conducted by FPInnovations assessed the use of single wide-base tires on two 8-axle B-train tractor-trailer combinations. The results showed an average 5.11% fuel improvement.

Low Rolling Resistance Tires

All major tire manufacturers now offer fuel-efficient tires with approximately 20% less rolling resistance than conventional tires, and they claim fuel savings from 4 to 12% when compared to normal tires. Since most of the fuel savings are the result of a more efficient tread design, as the tires wear, the improvement in fuel economy decreases to the point where it is the same as regular tires when the treads are depleted. Therefore, these savings are only realized for half the tire life.

FPInnovations fuel consumption tests resulted in up to 2.4% improvement in fuel economy for tractor-trailers equipped with one brand of these tires on the drive axles only, compared to normal tires.

Scope

The benefits of wide-base and low rolling resistance tires on line and regional hauling were fully demonstrated. 

However, wide-base and low rolling resistance tires are showing a steady growth in market share as more manufacturers introduce new products and as more sizes become available. Initially designed exclusively for on-highway applications, these tires are now entering new markets, such as on/off-highway travel, refuse haul, and urban buses.

Return on Investment

The decision to purchase fuel-saving technologies should be based on the payback period, i.e. how long does it take for the technology to pay for itself.  For consumable items, such as tires, the payback period must be reached before the service life of the item is consumed for it to be considered a worthwhile investment.

The following presents payback calculation examples for wide-base and low rolling resistance tires.

Common assumptions:

• Tire life for wide-base and low rolling resistance tires is comparable to regular tires and we will assume 200 000 km for this example. We assume an average mixed fuel consumption of 34 L/100 km.
• For an annual mileage of 200,000 km, we assume that the test results of the track-test would apply only under similar conditions, such as trips done on roads with a posted maximum speed of 80 km/h or more: 80% of the annual mileage, which gives 160 000 km. However, for low rolling resistance tires this is divided by 2 since, on average, the initial savings are only realized for half the tire life.

Wide-Base Tires

• For new vehicle purchases, the unitary cost for wide-base tires including rims is less than dual tires. If purchased as a replacement to dual tires for an existing vehicle, the purchase of wide-base tires will be less than dual tires by approximately $100 and the cost of new rims to accommodate the wide tires will be about $400 per wheel end. Therefore, in a replacement scenario, wide tires will add $300 in cost per wheel end, which means $2 400 per tractor-semitrailer combination. This additional cost can be spread over several replacement cycles, depending on the age of the vehicle.
  For our example, we will consider only one cycle.
• Certified track-test fuel savings results obtained at constant high-speed for wide-base tires: 9.7 %.
• The annual fuel savings would be 5 277 L:
   
• At a diesel fuel price of $1.10/L, the annual savings would be: 5,277 L x $1.10/L = $5 805.
• The payback period would be (in a replacement scenario): $2 400 / $5 805 = 0.41 years or 5 months.

Low Rolling Resistance Tires

• The cost of low rolling resistance tires is comparable to regular tires and they can be installed on the same rims as the normal tires
• Certified track-test fuel savings results obtained at constant high-speed for low-rolling resistance tires installed on drive axles: 2.4 %.
• The annual fuel savings would be 653 L:
   
• At a diesel fuel price of $1.10/L, the annual savings would be: 653 L x $1.10/L = $718.
• The payback is immediate.

The payback for wide-base tires 
is very quick (less than one month) when purchased as a replacement, because of the cost of replacing the rims. However, if operating in provinces where they can only haul reduced payloads, the payload penalty should be considered when purchasing wide-base tires. When purchased on new equipment, the payback is immediate since they are cheaper to purchase than a set of dual tires and rims.

The payback for low rolling resistance tires
is instantaneous because their cost is comparable to regular tires, and since they use standard rims, they can easily be retrofitted onto existing equipment.

Issues to Consider

Wide-Base Tires

Wide-base tires are narrower than a set of dual tires. In order to meet minimum axle width regulations, rims with a 2-in. (5.1-cm) offset are used. This changes the loading on the wheel bearings and may shorten bearing life with certain axle designs. Users that have experienced this problem resolved it by purchasing new and different type of bearings. If wide-base tires are to be used exclusively, wider axles (83.5 in. wide as opposed to 77.5 in.) can be specified on new equipment and the use of offset rims is not required. Governments in Canada are considering amending their vehicle weight and dimension regulations to accept lower minimum axle widths for wide-base tires.

Low Rolling Resistance Tires

Low rolling resistance tires do not present similar issues as their fit and operation are the same as regular tires.

Specification Considerations

Tire tread design plays a significant role in fuel economy. More aggressive tread designs tend not to be as fuel efficient as less aggressive designs. Therefore, tires with aggressive treads should be avoided unless the application warrants their use.

Wide-Base Tires

Tire sizes and tread designs are available to replace all the common sizes of dual tires for on-road use.  They can be used either on drive or trailer axles.

Low Rolling Resistance Tires

Low rolling resistance tires are available for all axle positions, steer, drive and trailer, and the same sizes are used as with standard tires.

Regulatory Issues

California has regulations that trucks operating in the state are equipped with energy efficient tires, and both wide-base and low rolling resistance tires meet this regulation.  The requirements vary depending on the age of the tractor and trailer and can be accessed through this link: http://www.arb.ca.gov/cc/hdghg/hdghg.htm.

To be eligible for United States Environmental Protection Agency (EPA) SmartWay^SM certification, options for low rolling resistance and single wide tires, with aluminum wheels, are encouraged but optional.

Wide-Base Tires

In Canada, legal axle weights are reduced in some provinces for vehicles with wide-base tires.  In Quebec, a special permit is currently required for vehicles equipped with wide-base tires to operate at full axle weights. This permit can be purchased for $10/vehicle. The Ministère du Québec plans to imodify its weight and dimension regulations in the coming years and the special permit for wide-base tires will no longer be required. The following table outlines the provincial weight restrictions for wide-base tires.

In the United States, on federally regulated highways, a typical tandem axle combination with wide-base tires can operate at full axle weights (15 500 kg) in all 50 states.  For some non-tandem axle combinations, wide-base tires may not comply in certain states.

Low Rolling Resistance Tires

Low rolling resistance tires are operationally no different than regular tires. They are subject to the same regulations as regular tires and can operate at the same axle weights throughout North America.

              Provincial weight regulations for wide-base tires

Jurisdiction	Type of axle
	Single			Tandem			Tridem
	Single wide tire (kg)	Dual tires (kg)	Penalty (kg)	Single wide tire (kg)	Dual tires (kg)	Penalty (kg)	Single wide tire (kg)	Dual tires (kg)	Penalty (kg)
Newfoundland and Labrador	7700	9100	-1400	15400	18000	-2600	23100	26000	-2900
Nova Scotia	7700	9100	-1400	15400	18000	-2600	23100	26000	-2900
P.E.I.	7700	9100	-1400	15400	18000	-2600	23100	26000	-2900
N.B.	7700	9100	-1400	15400	18000	-2600	23100	26000	-2900
Quebec (permit)	10000	10000	0	18000	18000	0	26000	26000	0
Ontario	9000	10000	-1000	18000	19100	-1100	26000	26000	0
Manitoba	7700	9100	-1400	15400	17000	-1600	18000	24000	-6000
Saskatchewan	7700	9100	-1400	15400	17000	-1600	23100	24000	-900
Alberta	7700	9100	-1400	15400	17000	-1600	19000	24000	-5000
B.C.	7700	9100	-1400	15400	17000	-1600	23100	24000	-900
Northwest Territories	6600	9100	-2500	12000	17000	-5000	18000	24000	-6000
Yukon	7700	10000	-2300	15400	17900	-2500	21900	24000	-2100
M.O.U.1	7700	9100	-1400	15400	17000	-1600	-	24000	-

1. Memorandum of Understanding on interprovincial vehicle weights and dimensions.

Maintenance Considerations

Maintaining tire pressures according to manufacturers’ recommendations is imperative to optimizing fuel economy and tire life. Use of a tire pressure maintenance or monitoring system is recommended because it will ensure tires are properly inflated and alert the driver if a tire is underinflated.

Wide-Base Tires

The time required to install a wide-base tire is comparable to a set of dual tires, and it is easier to check tire pressure of a single tire than a set of dual tires. Wide-base tires are 30 to 45 kg lighter per wheel end than a dual-tire assembly, but wide-base tire and rim assembly can weigh as much as 110 kg, which may make it difficult for one person to handle.

In some rural areas, finding a replacement wide-base tire may be difficult, since local tire shops may not stock them.  Under these circumstances, a wide-base tire can be temporarily replaced with a set of dual tires and rims.

Numerous reports have been made regarding tire wear.  A study conducted by FPInnovations found that the tires wore (tread depletion) at the same rate as a set of dual tires.  However, the wide-base tires in the study had a 1/16-in. shallower tread depth than dual tires; therefore, they required earlier replacement than the dual tires.  Manufacturers now have wide-base tires with the same tread depth as their regular tires.

If a company is undergoing a transition from single to wide-base tires, it is required to inventory both tire types during the transition period and this may lead to higher carrying costs.

Wide-base tires can be recapped; however, experience with recapped wide-base tires is limited.  It is also unknown how many times a casing can be recapped.

Low Rolling Resistance Tires

Low rolling resistance tires can be recapped with fuel-efficient tread designs that will maintain their low rolling resistance and fuel efficiency.

According to manufacturers, the life expectancy of low rolling resistance tires is the same as regular tires.  This claim has not been verified by independent testing.

If undergoing a transition from regular tires to low rolling resistance, a company would be required to stock both tire types during the transition period to avoid tire mismatching.  Mismatching of tires occurs when two unlike tires are installed onto the same dual assembly.  Even though the tires are the same size, there are small differences between unlike tires, such as tread design and tire circumference, which will result in irregular wear and potential failure.  Tire manufacturers strongly advise users not to mismatch tires.

References

Bridgestone Firestone North American Tire LLC. 2008. Tires & truck fuel economy – a new perspective? Real Questions, Real Answers, Special Edition Four.

Kenworth Truck Company. 2008. White paper on fuel economy.

Surcel, M.-D., Michaelsen, J. 2010. Evaluation of tractor-trailer rolling resistance reducing measures.
Paper no. 2010-01-1917. SAE 2010 Commercial Vehicle Engineering Congress & Exhibition, October 5 –6, 2010. Rosemont – Chicago, IL.

Surcel, M.-D.; Provencher, Y.; Michaelsen, J. 2009. Fuel consumption track tests for tractor-trailer fuel saving technologies. Paper no. 2009-01-2891. SAE 2009 Commercial Vehicle Engineering Congress & Exhibition, October 6–8, 2009, Rosemont – Chicago, IL.

The Goodyear Tire & Rubber Company. 2008. Factors affecting truck fuel economy. http://www.goodyear.ca/truck/pdf/commercialtiresystems/FuelEcon.pdf (accessed November 2010).

Web site of SmartWay Transport. Verified aerodynamic technologies.
http://www.epa.gov/smartway/transport/what-smartway/verified-technologies.htm#advanced (accessed November 2010).

Date modified:

2012-03-09

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