Fuel-efficient tire regulations and rolling-resistance ratings

The California Energy Commission (CEC) has moved another step closer to introducing a draft proposal for rating tires for fuel efficiency.

The State of California may well lead the nation, introducing a draft proposal for rating tires for fuel efficiency. The proposal will be the topic of discussion in a June 10 workshop presented by the CEC. (We know the federal government is also working toward a proposal but that is not expected out before the end of the year.) The California Energy Commission has been working diligently on a proposal through the Assembly Bill (AB) 844 Statutes of 2003. To this end, the CEC’s own research, and deliberations with tire manufacturers and retailers, and interested parties have formed the basis of the draft proposal.

Consumer Reports Auto Test Center was asked to be part of the proposal process as we are the only independent group that rates tires for both performance and rolling resistance.

Highlights.

• The ratings process will cover all passenger (P) and light truck (LT) tires available for sale in California, excluding winter tires; space-saver and temporary spare tires; tires with wheel sizes of 12-inches or smaller; motorcycle tires; and tires manufactured for use on off-road-use-only vehicles.
• There will be a rating system for each tire size designation and load index (load capacity). Tires will be ranked by lowest to highest rolling resistance (most to least efficient tires). Those rated as a “Fuel Efficient Tire” will have a rolling resistance force within 15-percent of the lowest rolling resistance tire for that specific size designation and load index.
• Tire manufacturers will be required to submit rolling-resistance data on every tire size within every model line sold in the state. Data will be reported by product SKU (Stock Keeping Unit), a unique number identifying a manufacturer’s tire model, size, and specific features. 
• The determination of a tire’s rolling resistance is measured using ISO 28580 rolling-resistance test protocol or produced by calculation (i.e. numerical modeling).
• Manufacturers must submit information on effected tires by July 1, 2011.  New tires will require submission of data prior to being sold in California.

What’s it mean to consumers?
Aside from Consumer Reports’ own tire rolling-resistance ratings, there are few other avenues open to consumers for information on this subject right now. The CEC proposal will be much more comprehensive, essentially covering most tires sold for light-duty vehicles and since what is sold in California is sold elsewhere around the nation, the availability of the data should have broad appeal.

The negative impact could be the misunderstanding tire rolling resistance and the compromises that come with some tires that have very low rolling resistance. In general, consumers should understand that as a rule, a 10-percent reduction of rolling resistance can improve vehicle fuel economy by only one to two percent. But typically consumers purchasing low rolling resistance tires should not expect a huge windfall savings in fuel costs. Also, some tires trade-off key performance features like tread-life and wet-grip for low rolling resistance.

The CEC is mindful of the trade-offs some tire manufacturers make for achieving low rolling resistance vs. traction and tread-life,  but technology is at the crossroads where some tire manufacturers are closing-in on breaking down those compromises. The CEC believes the tire efficiency rating system will encourage a competitive atmosphere for tire manufacturers to achieve the coveted “Fuel Efficient Tire” rating. Consumer Reports has already been asked to participate in this next phase, as well.

Consumer education will be an important part of the Tire Efficiency Program. The CEC understands the success of the program is in educating the consumer on what tire rolling resistance is, expected fuel savings, and possible trade-offs associated with low rolling resistance tires. The CEC’s plan is to make public access to the entire database for consumers interested in the researching tires which will include rolling resistance and tire sidewall data.

Bottom line:
Rolling resistance should not be the primary reason for a tire purchase. The most important considerations are safety-related performance features including dry- and wet-braking, hydroplaning resistance, handling, winter traction if applicable in your region, and tread-life. Low rolling resistance should be a secondary consideration in your tire-buying decision.   

The CEC would like to know your interest in the Fuel Efficient Tire Program and you can make comments here or in TireTalk (an expert forum available to online subscribers).  

Before buying, be sure to consult our car, truck, and winter tire ratings and buying advice.

—Gene Petersen

Comments

[david]

This is great news for Consumer Reports. Hopefully, CR will be compensated by the state of CA. So, CR will have more budget for tire testing, which means better for us readers. Maybe down the road, we'll get an on-going annual testing of new tires in all categories.

[Cale]

Great blog! The data will be very interesting to get. But buying a fuel efficient tire isn't a substitute for proper tire care. Some drivers will still run them a couple pounds under (giving up the fuel economy benefit) or a couple pounds over (trading a single mpg gain for substantially reduced safety/performance). I think tire pressure monitoring would be a better investment of resources than all this testing. I don't know how you'd get the systems mandated or installed but tire safety and economy, it strikes me at least, is all about tire care and maintenance.

[Harry]

Rolling resistance info on tires is very important to me. I tried very hard to find this information when I bought tires, but could not find usable information.

A few percent chance in fuel economy may not seem like a lot. But it adds up to a lot over many miles. This is valuable to the consumer, the environment, and to the nation as a whole.

[Tom]

I have a 2003 Honda Accord EX 4cyl with 60,000 miles. It has 16 inch allow wheels. The original tires are Michelin with a 91V rating and have tread readings now of 5 front and 6 rear. They are good tires, but the ride is a bit noisy and stiff. A couple of tire shops have recommended that I get the 92H version of the Michelin Primacy that they believe will perform well and will provide a somewhat better ride. The Honda dealer advised me that putting the 92H on the car would work just fine and he has seen a number of cars with that tire. Yes there could be some performance impact, but he did not believe it would be significant.

You have said absolutely to never go below the manufacturers speed rating.

The H version of the Primacy is also $40 per tire less expensive. If I have to stay with a V rated tire, I might be forced to more to something like a BF Goodrich T/A.

While mine is a specific question for this model, I'm assuming others think about the speed rating question as well.

Thanks

Tom