Article

Fuel Savings vs. Shorter Tire Life

June 2015, TruckingInfo.com - Feature

by Jim Park, Equipment Editor - Also by this author

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Can low-rolling-resistance tires reduce tire costs and save fuel? Some say yes; other disagree.
Can low-rolling-resistance tires reduce tire costs and save fuel? Some say yes; other disagree.

Are low-rolling-resistance tires a cost-effective proposition? It’s not an easy question to answer. The tire people tell us that the additional upfront cost coupled with the (usually) lower miles to removal are offset by the fuel savings accrued through lower rolling resistance. But can we prove it?

Lower miles to removal seems to be the big hurdle. You pay more for the tire but get fewer miles out of it. At least, that’s the perception. Is it an accurate one? Judging by the results of a recent fleet survey conducted by the American Trucking Associations’ Technology & Maintenance Council, fleets might be off the mark in assuming that LRR tires aren’t going the distance.

Generally speaking, LRR tires are presumed to cost about 15% more than standard tires, with a reduced tread life of about 30%. The presumed 3-4% fuel savings potential of these tires is believed to offset the two negatives.

The findings of the survey were a little surprising, and in some ways contradictory. They showed that in all cases except trailers, low-rolling-resistance tires actually outran standard tires, which sort of lays to rest the assumption that they don’t last as long.

Yet at the same time, a majority of fleets reported that fuel savings did not offset the cost of the “presumed” shorter-than-standard lifespan of the LRR tires.

Contradictory results

Peggy Fisher, president of Tire Stamp and regular contributor to TMC’s tires task force work, has a possible explanation for the apparent contradiction.

“Among other things, the survey showed that a sizeable number of fleets (29%) do not know what their fuel economy is -- which is very odd in this day and age,” she says.

Since that’s a relatively easy thing to measure, and a figure fleets live and die by, one might have good reason to question how good a job fleets do at measuring tread life, which is a more labor-intensive and difficult calculation.

“Therefore, it is not surprising that they didn’t know they are getting better tread mileage on low-rolling-resistance tires than non-low-rolling resistance tires.”

Only the trailer tires were reported as getting less tread mileage, she notes, “and it just so happens that we all know that trailer tires are the worst maintained in the fleet.”

Fisher is quick to point out that there is a direct correlation between tire maintenance and tire life. If maintenance is poor, tire life will be, too.

“We know from studies done in previous years that maintenance of truck tires is poor, with only 44% of tires in an earlier study found to be within +/- 5 psi of target pressure,” she points out. “If tire maintenance has not improved much since 2002 when that study was done – and I do not think it has significantly -- then it is not surprising that fleets are not getting the fuel economy and tread mileage they had hoped for, since both tread mileage and fuel economy are seriously impacted by improper tire inflation.”

Fisher says 51 fleets responded to the survey, the vast majority being linehaul and regional operators running Class 7-8 vehicles. Of the responding fleets, 43% had 100-499 power units while 41% had 500 or more power units. Some 85% of fleets indicated they were running LRR tires, and 63% of those fleets have 50% or more of their vehicles on such tires.

Looking at the numbers

For steer tire mileage, the survey showed mileage of 106,730 for standard tires and 114,063 for low-rolling resistance.

Fleets were asked to check mileage range boxes (<50,000, 50-100,000 and 100,000-150,000 miles), so the exact number of miles the tires ran may not be reflected in the results. Fisher calls the results a “guesstimate” based on a weighted average for each group.

“The numbers seem a little low, but the interesting thing is that low-rolling-resistance tires, in general, outperformed the standard tire by almost 10%,” she said. “The results of the drive tire section showed similar results.”

The drive tire section of the survey broke out single and tandem drive axles as well as standard, LRR and wide-base single tires. For both single and standard axle trucks, wide-base singles performed the best in terms of miles to removal – 218,750 for tandems, 192,857 for singles. They were followed by LRR tires, at 212,500 for tandems and 155,882 for singles, with standard tires bringing up the rear with 203,205 miles and 152,630 miles.

On single drive axles, wide-base single tires outlive the others by quite a margin. The range wasn’t quite so stark for the tandem axles.

“I grouped these together for the benefit of fleets considering going from 6x4 to 6x2,” Fisher says. “You can infer from these results that you will see a mileage shortcoming in the single-drive axle group, but that should hardly come as a surprise.”

In looking at trailer tires, the victory went to standard tires. They outperformed LRR tires by an average of close to 4,000 miles, and outlived the wide-base single tires by about 7,000 miles.

“Trailer tires revealed results opposite to what we saw at the other wheel positions,” Fisher says. “Maybe this is where people get the perception that they get poorer mileage from LRR tires. Are the trailers not performing as well because they are not being maintained as well? We don’t know for sure that this is the case, but we do know that trailer tires are typically not well maintained.”

Perceived value?

When asked to report on the fuel savings they realized with their tire selections, fleets indicated low-rolling-resistance tires averaged a 1.9% improvement in fuel savings and 2.2% with wide-base singles. The next question was, “Did the fuel savings meet your expectations?” About one-third (29%) said yes, while slightly less than half (42%) said no. Another 29% said they were not sure.

“These results blow my mind,” Fisher says, leaving little doubt of her dismay with the high level of uncertainty. “Nearly one-third of the group who bought LRR to reduce fuel consumption didn’t know if the tires were saving them money or not. It seems to me you’d be monitoring that a bit more closely.”

The final shocker came with the question, “Did fuel savings pay for lost tread rubber?” Only 40% said yes; 60% said no. That’s hard to reconcile with the fact that in most cases the LRR tires ran more miles than their standard counterparts – with trailers being the notable exception.

It would seem that if some fuel economy improvement is a given with fuel-efficient tires compared to standard tires, the additional tread life would be a bonus.

“If they were responding to that question based on trailer tire performance, I might tend to agree,” Fisher says. “But if we’re considering all wheel positions, I think fleets might be doing better than they think, based on these numbers.”

Given the potential fuel savings from LRR tires, fleets should be very careful about how they evaluate the tires’ performance. Only accurate application-to-application and model-to-model comparisons can be considered valid for calculating savings. There’s no point in comparing a Bridgestone to a Goodyear, for example, because the performance difference could reside in the tires themselves. 

If the TMC survey is valid, then there could be a lot of fleets leaving money on the table based on nothing more than a perception that LRR tires don’t last as long.

Comments

  1. 1. Paul Juhan [ June 09, 2015 @ 02:38PM ]

    did you ever think that your drivers are just hitting more debris than normal and the lower amount of rubber is making it easier to penetrate.in this day and age the driver can make or break fuel mileage with all the aerodynamic gadits that you have on your truck won't make any difference

  2. 2. Matt Putnam [ June 09, 2015 @ 05:43PM ]

    Good article, Helps us in the industry think.

  3. 3. Cliff Downing [ June 09, 2015 @ 07:44PM ]

    Tire maintenance and pressures are key along with sensible driving. I got 210,000 miles on my last set of Michelin Steer tires, currently 200,000 on this set with still 11/32nd tread left. My Michelin wide based are original put on at factory, with 410,000 miles on them and still 11/32nd tread left also. I am meticulous about checking tire pressures, daily during seasonal temperature changes, and follow the recommended load / pressure charts put out by Michelin. Maybe a little unrealistic for the average fleet to require drivers be this vigilant, but it does pay off.

  4. 4. Mike [ June 10, 2015 @ 05:03AM ]

    100,000 miles for a set of steer tires? LOL? Does anyone at these outfits inspect their tires, along with pressures? How about alignments and tire balancing? None of this is that expensive, and just common sense in my book. But what do I know, eh?

  5. 5. Steve [ June 13, 2015 @ 09:36AM ]

    The lower the rolling resistance,the lower the traction. The article doesn't mention the lower traction on snow and ice or what the expense of the accident increase is.

 

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