OK guys, let me fill you in on the problem.
The Test: There are many tests for Rolling Resistance. But to do a comparison, the test used has to be the same. Change the load or change the inflation pressure and you get a different answer. Further, the equipment used either has to be the same or correlated to the same piece of equipment.
Tire Size: Even exactly the same tire tested on the same equipment, with the same test procedure varies according to size. Even if you divide by the test load to get a coefficient (Commonly abbreviated RRC), the value varies according to size.
Publishing the results: Do you publish the RR value, or the RRC, or give it some kind of rating?
All these question are being addressed by a variety of folks - The California Air Resources Board (CARB), NHTSA, the Rubber Manufacturers Association(RMA), etc.
Believe it or not, the easy question (question #1 - the test) there is disagreement between all the parties involved. The RMA has recommend a single point test to be conducted by any test facility with a correlation to a single facility and RRC would be reported. CARB wants a full 4 point test tested at ONE Facility. And NHTSA wants a single point test with a correlated value, but they want the results reported in RR.
I suspect they will all get over their differences at some point.
But the tough question - tire size - has everyone in a quandry. It has been estimated that if EVERY test facility in the world were to be utilized 24/7 for the single point test, it would take over a year to test all tires CURRENTLY available. That means the NO dveleopemnt work on new tires would take place - not to mention how long it would take to test any new products that would be come on stream in that year.
All parties agree this is not acceptable.
It has been proposed to first test any tire that advertises a fuel economy advantage or a "green" type of advertising, following up with the other tires later. Some tire manufacturers do not want to do this. Since a lot of current advertising has this, it is still a very large number.
Nevertheless, the system to inform the consumer is moving forward. It has been proposed that either a "Star System" or a "Number System" be used.
The "Star System" would have a series of stars to indicate the level - 5 Stars is great, 1 star would be poor. This would also apply to other UTQG type ratings - Treadwear and Traction (Temperature is currently doubly reported when speed ratings are used.)
The "Star System" could be implemented quickly because the system is coarse enough that tire size could be ignored.
The "Number System" would involve the same type of system used for Treadwear - increments. The problem here is that too small of an increment would mean that EVERY tire would have to be tested. Careful selection of the increments might result in less testing - and quicker results to the consumer.
And that's where we are. The tire manufacturers are doing testing to see what increments they think will work. (Hint: When tire manufacturers do RR testing, they generally test against one size to get an idea where they stack up.)
So what do you think?
Would you guys like to see results quickly using the start system?
Or are you willing to wait a couple years (may be up to 5) to get the Number System?
Oh and to address LT4 Vettes remark - don't bother to call the tire manufacturer. Since they haven't tested all the tires and haven't agreed to a test procedure, they don't have numbers to report.)