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Friday, July 23, 2021

Is better tire wear AND better fuel Economy possible?

 We all see posts from people wanting better tire wear and better fuel economy. Here is some information from a friend "Dr. Joe"

Wear, traction and rolling resistance are interrelated (but adjustable) factors determined mostly by tread material properties fixed during the design stage of tire development. The rubber chemist's enduring dilemma has been that enhancing one tread attribute influences the other two – usually adversely. Marketing professionals tend to use the term “balance” rather than “tradeoffs” to describe these conflicting variables. Based on my reading of recent industry press releases, tire wear and traction seem to be playing “second fiddle” to rolling resistance in today’s push for “greener” tires – even though fuel efficiency has not been a top priority for US consumers. It is, however, well known that good tread wear resistance is important to motorists purchasing replacement tires. Contrarily, because of CAFE mandates, OEMs consider tread life subordinate to rolling friction in their procurement of new car tires. Unarguably, any decrease in wear out mileage increases the frequency of tire replacement and unwelcome scrap generation.
Tire traction, nonetheless, is important to safety conscious motorists; it is constrained by road conditions which control traction limits encountered by given tread compounds and patterns. These can be optimized for wet, dry or snow performance. While over 80% of tires in service in the US are rated at the UTQG traction level “A”, only 15% are rated at the highest level “AA”. Surprisingly, no real-world data exists indicating that tires with higher rated traction grades are less involved in highway accidents than lower rated ones – with snow tires an exception as they are not UTQG rated, For improved all-weather traction, so-called “rain tires” have been touted on-and- off over the decades, and promoted extensively by U. S. Rubber (now Uniroyal) beginning in 1965. Wet grip was achieved, then and now, by sacrificing tread wear. While this is an acceptable trade-off in Europe, US consumers have consistently rated long tire life more important than tire grip; and with relatively cheap fuel, rolling resistance tends to be a non-issue for individual tire buyers. The most common reasons reported by the influential Consumer Reports (2019) for selecting a particular replacement tire brand are price (44%), tread life (40%) and brand trust (31%). Similarly, the respected J. D. Power new car owner survey (2021) rates the top three tire satisfaction metrics as wear, ride and traction (in order of importance).

Regarding tread life, surveys of large numbers of scrapped consumer tires usually show that the majority are three to four years old when replaced. Since Americans drive between 11,000-12,000 miles per year on average (according to FHWA), this means that most passenger car tire wearout mileages occur between 33,000-48,000 miles. If light vehicle tire lifespans could be increased an additional year, demand for new tires would be reduced with lessened environmental impact. Also, tires become more fuel efficient as they wear. I wonder what an environmental and economic cost-benefit analysis of tire life extension might yield? Mainly due to existing and proposed government mandates, US consumers have been, or will be, forced to unwittingly accept reductions in tire life with increased costs in concert with lower rolling resistance. Then we encounter further demands placed on EV tires – which need improvements in tread wear, traction, and rolling resistance compared to their ICE powered counterparts. Additionally, the
California Energy Commission once again announced plans to implement a program to ensure that replacement tires sold in that state are as energy efficient as OE tires. This will only exacerbate the confounding situation facing consumers valuing tire life.
Ponder Michelin’s
transitional development of the radial tire after WWII. Wearout mileages were doubled while rolling friction was reduced by 25% compared to existing cross-ply tires. Could the industry now develop tread compounds and/or tire constructions that at least make desirable improvements in both wear and rolling resistance without comprising grip? Unexpectedly, Bridgestone, Arlanxeo and Solvay have just announced material technology that claims to achieve just that; up to 30 percent better wear efficiency and six percent reductions in rolling
friction. Hopefully, this technology will be licensed to others if the claims are justified
.


Joe Walter enjoys teaching Vehicle Dynamics and subjects related to tire materials and mechanics at The University of Akron. He previously served as Vice President and Director of Bridgestone Americas Research Center in Akron and President of its European Technical Center in Rome. Joe obtained graduate and undergraduate degrees in engineering from Virginia Tech a long time ago.

While Dr. Joe's article is aimed at the passenger and light truck vehicle market you can be assured that as new technologies are developed in one sector of tire design the features and advantages soon spread to other product lines. 

##RVT1010

Friday, July 16, 2021

Airless tires? Reality? or just a pipe dream for RV owners

 A friend recently sent me a copy of an article from the Akron, Ohio daily paper The Beacon Journal.


 I am in Colorado, ending a 3 week working (giving tire seminars) trip, and celebrating with my wife, our 37th Anniversary sightseeing vacation, so missed the article on "Airless" tires. 

 

Wait! 

 

 What do they mean "Airless"? Could we soon be absolved of needing TPMS in our wheels? What will I write about if I can't keep complaining about people not using the proper inflation?

This sounds too good to be true. Well it is true...Sort of. It appears that the latest effort from Goodyear to develop a reliable airless tire is aimed at some "self-driving" vehicles that can transport goods and maybe even people around a small ares of a town or city.

While air filled "Pneumatic" tires have been around since 1847, the background on "Airless tires" is many decades old with many tire companies all trying to be the first to crack to code and present a reliable tire that can function like a regular tire when inflated with air. So far everyone seems to run into the same wall of limited speed or limited durability. While Goodyear hasn't released any specifics, visually their latest effort "resembles similar products being tested by other companies in its open-spoke design and flat tread" according to the picture (above) from the press release and an article in Rubber & Plastics News.

There are many "Airless" tires already in use today. In fact, in 1972, I worked on the Flat-Proof tires for the then brand new Dallas-Ft Worth airport for their passenger transfer system of driver-less vehicles that circulated the airport.  The tires had no air inflation but were filled with a heavy duty "foam-rubber". Other applications of airless tires include lawn mowers and numerous construction vehicles.

 If you wanted, you could order some Airless tires today for your forklift truck and would never need to add air or worry about the tires being punctured and going flat.

One thing that is almost universal with these applications is that they all have significant restrictions on operation speed, This limit is usually below 20 mph and if operation at this speed is required, the distance traveled or even the roadway used  must be strictly controlled.

So, it looks like we RV folks need to continue to wait for the scientific breakthrough that is needed to put tires on our cars, truck , trailers and RVs that no longer need air inflation to carry the load.

##RVT1009