The debate over the value of low rolling resistance (LRR) tires has subsided to a dull roar since they were first introduced about 20 years ago. Initial concerns about fewer miles to removal and stiffer ride quality were mostly mollified as fleets gained experience with the tires.

But traction concerns linger among many Canadian fleets, for fairly obvious reasons.

LRR tires came to market in the mid-2000s in response to fuel efficiency and environmental concerns. In principle, a tire with lower rolling resistance would require less energy (fuel) to power, thus saving fuel and reducing carbon dioxide emissions.

In 2010, the U.S. EPA launched its SmartWay program, which certified tires meeting specific fuel efficiency criteria, accelerating the adoption of LRR technology in the industry.

In 2017, U.S. federal greenhouse gas (GHG) emissions and fuel efficiency standards began requiring manufacturers to improve vehicle efficiency. This bumped the uptake (not always voluntarily) of LRR tires.

Early adopters of LRR tires were not universally pleased with their performance or the return on investment (ROI) on the tires. Since one of the primary characteristics of LRR tires is a thinner tread, fleets were unhappy about losing miles to removal. With less tread rubber from the beginning, the thinner tires were bound to come off sooner.

It took a while for the math to emerge, but eventually the figures proved the fuel savings resulting from the more efficient tires more than offset the cost of replacing the tire more frequently.

Fleets with strong tire management programs easily saw positive results. Fleets with a haphazard approach to tire management had difficulty proving the hypothesis.

In it’s 2020 update to a Confidence Report on LRR tires, the North American Council on Freight Efficiency (NACFE) noted that industry had to change the way it viewed ROI on tires.  

“Calculating the life cycle cost of tire ownership is critical. Traditionally, tire per-mile cost is defined solely in terms of their initial purchase price, and as tire replacement may be more frequent with LRR than with non-LRR tires, the value of the LRR options has been under-recognized by the industry,” the report noted.

If fleets omit the fuel savings from the ROI calculus, the ROI doesn’t look so good. This of course can be challenging for fleets that don’t closely monitor factors like truck and driver mpg, tire inflation pressure, and tire wear trends.

Traction matters to Canadians

One of my favorite quotes ever from a tire engineer came from Guy Walenga, Bridgestone’s former director of engineering, commercial products and technologies. He’s retired now, but he always had a pithy comment to offer.

“More traction might be better and less might be worse, but we don’t know what’s ideal,” he told me back in the mid-aughts when the debate over traction and LRR tires was at its peak. “There is no ‘normal’ for traction. It’s difficult to quantify how much we need, but we sure know when we don’t have enough.”

Drivers fret about traction all the time. They get excited even if they just perceive that a certain tread type doesn’t look grippy enough. And while it’s true that many of today’s LRR drive tires don’t look “grippy,” advanced tread designs and rubber compounds do maintain “adequate” traction.

Manufacturers now build tires with tightly packed lugs rather than deep widely spaced lugs. When tread lugs are packed tightly together, they support one another, and tread-squirm is minimized.

While it might be hard to imagine, as individual tread blocks, or lugs, contact the pavement, weight bearing down on the tire and the torque from the engine cause some distortion in the shape of the lug. The tread literally squirms as the tire rotates. The energy required to deform the lugs comes from the fuel tank. 

The more the tread blocks are supported by each other, the less distortion occurs.

Some manufacturers use a tread design with “microsipes,” tiny gaps in the tread face the provide nearly the same grip and traction as a beefier looking lug tread — without the fuel-economy sapping tread squirm.

These are good examples of how tread design can lower rolling resistance with minimal traction reduction.

One of the other hallmarks of an LRR tire is shallower tread depth. While a non-LRR tire, or traction tires for severe service, may have a tread depth of up to 30/32nds of an inch, a typical fuel-efficient LRR tire is more likely to have a tread depth of 20-to 24/32nds.

Generally, shallower tread provides less traction in snow, and with everything else being equal, will run fewer miles to removal simply because there is less rubber there to begin with.

However, tread rubber compounds have improved over the years, which enables engineers to specify stiffer, more resilient rubber for the tread faces capable of running more miles per 32nd of an inch of rubber. There can be a traction trade-off here as well, albeit it a smaller one today, as harder rubber tends not to have all the traction attributes as softer compounds.

Is adequate traction good enough? Certainly not in every case. Fleets operating in B.C. or in Quebec’s North Shore region in winter would have plenty of good reasons to stick with their gnarly, grippy lug drive tires.

That said, most fleets running stateside would see fuel economy benefits from LRR tires without compromising traction under most operating conditions.

Tires’ contribution to fuel savings

As NACFE notes in the LRR Tire Confidence Report, tires’ rolling resistance accounts for roughly one third (30-33%) of the truck’s total fuel consumption. And according to Bridgestone’s calculations, if rolling resistance can be reduced by 5%, fuel consumption can be reduced by 1.3-1.7%.

Part of the challenge in testing and evaluating LRR tires lies in the relatively small gains that can be had. Also, it’s well known that tires become more fuel efficient — ie., less rolling resistance — as the tread wears down. They are at their most efficient when the tread is worn to the pull point.

To get a realistic view of the tire’s efficiency, you have to run it and track it from Day 1 to the end of its service life. That’s a very difficult task for fleets that lack sophisticated data management systems.

“Certain inaccuracies arise when measuring actual fuel burned without temperature compensation and precise mileage inputs. Also, weather, driver habits, varying weights and other vehicle condition parameters can sway the results,” NACFE notes.

“Fleets testing tires on their own do not always achieve statistically accurate results, thus their tire-buying decisions can be skewed by inaccurate, incomplete or corrupt data.”          

Which LRR tires are right for you?

It’s not just about rolling resistance. The tire’s performance must sync with the operation, driving locations, maintenance practices, budget and other priorities, such as fuel costs.

The best tire is the one that offers the best overall cost of ownership. That calculation has to include miles to removal, durability, and best estimates of fuel cost savings that will help offset the possibly reduced tread life of a LRR tire.  

Fleets also need to get the application right. Certain tires perform better in certain applications, such as the right combination of on- and off-road driving, or urban and highway miles.

If you’re still inclined to dismiss LRR tires on the basis of less traction and fewer miles to removal, here’s something to consider: If you’re over-inflating your current tires in the belief that higher inflation pressures will lower rolling resistance, you may be compromising traction and tire life by doing so.

Which is contrary to the reasons you might be avoiding LRR tires in the first place.

Yokohama offers a tire pressure app to help users calculate optimum tire pressure for load. It suggests, for example, dual tires in a fully loaded U.S. tandem axle (34,000 lb.) should be inflated to 80 psi, not 100. The higher number might be easier to remember, or provide a hedge against underinflation, but it could be compromising traction and tire performance.

Inflating to a pressure lower than 100 psi is a controversial stance, but Rick Phillips, former vice-president of sale at Yokohama, now retired, once told us it’s all about optimizing the contact patch of the tire.

“Most fleets run 100 psi in a drive tire, which is well overinflated for the maximum weight on tandem axle (U.S. loads). That may seem to improve rolling resistance, but it actually distorts the footprint, which reduces traction and increases tire wear,” he said. “If you run the tire at its design pressure, you run it the way it was designed to run, which gives you optimum traction, mileage and minimizes inflation-related irregular wear, so you get best performance over the life of the tire.”

If you’re worried about reduced traction and shorter tread life associated with LRR tires, you might just be wearing your current tires out prematurely believing that you’re contributing to your bottom line with with better fuel economy. Or. maybe not.

NACFE published its updated Confidence Report on LRR Tires in October 2020. At the time, the organization was bullish on the fuel-saving tires, and it remains so today. While acknowledging they are not for every fleet, the report states, “the perception of traction issues or driver acceptance problems is worse than the reality”:

• For general over-the-road goods movement, these LRR tires are performing well in terms of traction and driver acceptance.
• Traction for LRR tires may not be acceptable in certain applications, and as tread wears, traction will be further reduced, but this is true for any tire.

Further, NACFE acknowledged the purchase price of LRR tires may be higher than non-LRR tires, but stressed the increases acquisition cost can be overcome through fuel savings when considering life-cycle cost.

“Traditionally, tire cost-per-mile is defined solely in terms of the initial purchase cost and tire replacement, which may be more frequent than for non-LRR tires. But to account for the fuel savings, NACFE strongly suggests that fleets use a total life-cycle cost of ownership to make tire purchasing decisions,” NACFE advised.