California’s Energy Commission is examining the possibility of a government database and rating system for the fuel efficiency of car and truck tires, reports Modern Tire Dealer. “The foundation of a government administered product rating system is a comprehensive database providing reliable test results and objective information accessible to everyone. A solid analytical basis combined with full disclosure and transparency inspires the confidence required for a rating system to be successful,” says the CEC. “A ranking system driven by the ‘best in class tire’ can ignite a competitive spirit.” Under the CEC proposal, “all tires with an Rolling Resistance Factor (RRF) within 15% of the lowest RRF reported tire for that combined tire size designation and load rating will be rated ‘fuel efficient tire.'”
Manufacturers aren’t thrilled at the prospect, arguing that, if enacted, the rating system could add $20 million in industry costs for testing and data management. The Rubber Manufacturers Association is championing a “self-certification” system, in which tire makers would monitor each others’ rolling resistance claims. The RMA also points out that the National Highway Traffic Safety Administration (NHTSA) is developing a federal-level tire rolling resistance regulation and a California-only rule “may not be prudent.”
Now that they rate tires. Then rate engines. Then transmissions. Then CV joints. Then ECU. Then underbody …
Why not just slap more gasoline tax and let the car buyers figure out for themselves.
Are tire rolling resistance numbers available? Are they standardised? Is there a tradeoff between the rolling resistance and some other tire characteristics?
Why limit the comparison to a single tire size? How is rolling resistance affected by plus-sizing or minus-sizing? Did general wheel/tire size increase over last 5-10 years affect the fuel economy through increased tire rolling resistance?
@wsn:
although I like a gas tax, I also like a rating system to easily be able to know what I’m getting. Same w/ appliance energy ratings.
@ttacfan
The less the rollign resistance the more slippery the tire.
The November 2008 issue of Consumer Reports has a section where they rate different brands and types of tires based on several characteristics, one of which is rolling resistance. Every tire is a compromise for something, and when some tires scored better in rolling resistance they suffered in something else, sometimes several things, such as price, longevity, wet traction, etc. Check it out – November 2008 CR.
Can somebody please tell California to fix their own damn problems please? Is their no industry that they don’t try to be the tail wagging the dog?
–chuck
The coefficient of friction is determined by the interaction of two surfaces.
Is the state of California going to rate each and every roadway in CA? Hell, I know roads which switch between asphalt and concrete almost on a random basis….I’m talking the same road.
This is just another pathetic excuse for government workers to justify their pathetic existence. Let’s create another bureaucracy…why it’s for the “public’s own good”!! Right up there with rating reflectivity of paint.
Nice job Kalifornia.
>>> I guess we’ll need a bureaucracy now to monitor tire pressure too. How DARE you regulate the pressure in your own tires!!!…that’s the role of government! Why stop there…why not have the State of Kalifornia monitor which weight of oil you use in your engine? Just THINK of how “green” this will be.
@David Holzman
I don’t think that rolling resistance and the “slippery”-ness of a tire are necessarily related. Early LRR tires were known for high wear rates but I don’t hear that as much anymore. There is a lot of attention being paid to the area so trade-offs are not set in stone.
For example, increasing tire pressure lowers rolling resistance and, up to a point, also provides more grip.
@David Holzman
@midelectric
Two of my Prius-driving friends complained that Prius suffers from the cross winds on one particlar bridge in the Cleveland area. I have strong suspicion that it is, at least in part, due to the low rolling resistance tires.
I also noticed that when I replaced my OEM Goodyear tires with their Assurance TripleThreads, I noticed: a) much less frequent traction control engagement in rain and snow slush, and b) gas mileged dropped by almost 10%.
wsn: having a higher gas tax won’t help a vehicle owner figure out which tire will help him save gas. Having an advertised rolling resistance rating will.
ttacfan: Crr data isn’t generally available. Some groups have tested it independently, but test methods and testing equipment hasn’t proven comparable, so manufacturers don’t advertise something an independent lab might measure to be different. Every size tire will have a different Crr even within a single “design” tire or model line. If the RMA can condense on testing a single tire size they save a lot of money but can only compare designs against competitors. The variation among sizes of a model is likely greater than the variation between different models of a like size. From what I’ve been able to read/see tires with higher aspect ratio have a lower Crr, larger diameter tires have a lower Crr, and width may or may not have a trending impact.
Isn’t it true that, everything else being constant, rolling resistance decreases as tire pressure increases? Manufacturers can thus help their epa mileage ratings by specifying higher tire pressures. If the car then tends to skitter sideways because of pavement grooves or crosswinds…hey, not their problem; they met their government mileage target. I’d think this might be more of a problem with the cheaper economy models.
Edmunds had a “test the tips” article which debunked some mileage myths. Higher tire pressures leading to lower rolling resistance and greater fuel economy wasn’t substantiated.
http://www.edmunds.com/advice/fueleconomy/articles/106842/article.html#test2
Low rolling resistance = hard as NSFW rocks + no traction. You can also save gasoline by walking.
prediction: (higher mileage)^((penny-wise)+(pound-foolish)) == higher accident probability
It looks like California is following Europe here. Or is it the other way around?
https://www.thetruthaboutcars.com/eu-retreads-tire-labels/#comments
I’ve noticed that Nokian advertises their Z G2 ultra-high-performance summer touring tire as qualifying as “low rolling resistance” tire. I assume that this is according to a European definition of some sort (or maybe one that Nokian made up themselves, I suppose).
I can’t imagine that a UHP tire could be as slippery as most of the low rolling resistance tires you usually see slapped onto things like hybrids. So hopefully this means that there’s hope for good tires that are also efficient.
While I like the idea of informing the few consumers who would actually care, I fear that this is just one step along the way of mandating low-rolling-resistance tires. Like CAFE, that would mess up the tire marketplace, cost consumers money, and be of just about no use in conserving fuel.
Here’s a followup question: how does the rolling resistance between a properly inflated high-resistance tire compare to the resistance of an under inflated low-resistance tire?
Kali-for-ni-a, MYOFB ! Get a clue !
You wonder why Californians are voting with their feet ?
At the time of this writing, I’m attempting to get home from SF.
With the hills here you’d think they’d want INCREASED resistance. For those of you who have never been to sf, there are _VERY_ steep hills. Our automatic cobalt didn’t exactly inspire confidence on them, either.
When you can start rolling down the hill at 20-25mph and hit 40-50 if you don’t brake most of the way down the hill, I think i’d want to replace my tires with something a little more resistant to rolling.
No matter what, when you increase tire pressure, you decrease grip. Tires with very low pressures have more grip then when you fill them up. However, the car is not safe to drive, because the tire will want to fall apart. If the pressure is too high, the tire can also blow out. That’s why the manufacturer recommends a pressure that’s safe to drive on. In the summer, I go a tiny bit above that for the fuel economy, however, in the snow, traction is sacrificed greatly, and I lower it back down.
I just parked my Subaru into the garage for the next couple of months to save on insurance. When I worked at the dealership, I found out that the manufacturers greatly overfill the tires to prevent them from gaining flat spots. We had to let the extra air out of the tires before taking the car on the road. So I too used that idea and raised the tire pressure to 55psi. Obviously, the tires aren’t safe to drive on, but just rolling the car back and forth in my garage, the car is about as hard to push as a skate board.
I could see some high pressure tires resulting from any legislation that gets passed, but what are we going to do in the winter? We’ll have cars with these tires sliding around everywhere.
When you walk into Best Buy or Fry’s every appliance has its energy consumption clearly marked on the label. This is no different. Tires already have ratings for tread wear and winter traction.
It will give consumers information to make an educated choice. Most folks could care less and will just purchase whatever is on special at Wal-Mart, Costco or whatnot.
Now if they start to mandate LRR tires it becomes another issue.
Presently it is very hard to find any rolling resistance information on tires. Consumer Reports gives relative ratings with their black and red circles representation. Other than that, there is nothing.
The tire industry could get in front of this by developing a good relative rolling resitance measurement system and having manufacturers publish the data, but presently the data is almost impossible to get.
I’m all for consumers having the information needed to make informed decisions. The EPA should be all over this instead of leaving it up to California, but the EPA has ignored the issue.
My Accord V6 is rated at 240 hp SAE Net and about
206 hp wheel. It is said that tires eat up most of the difference. Where are the tests to prove?
Translation of positive tire rating: “Look for the union label!”
I hope they do it. The more I know about a tire before purchase, the better.
# David Holzman :
June 15th, 2009 at 1:49 pm
The less the rolling resistance the more slippery the tire.
Hear. Hear. Every “fuel saving” low-resistance tire I’ve ever bought was a nightmare in terms of braking performance. That’s not a trade-off I like making. And the extra price versus an “ordinary” tire, is, at this time, not worth the economy benefits. The differences just don’t equate.
midelectric :
June 15th, 2009 at 1:57 pm
@David Holzman
I don’t think that rolling resistance and the “slippery”-ness of a tire are necessarily related. Early LRR tires were known for high wear rates but I don’t hear that as much anymore. There is a lot of attention being paid to the area so trade-offs are not set in stone.
Decrease wear rates by making the compounds higher in silica and harder (and thus decreasing rolling resistance even further)? Please do. And make them ride like ice skates in the wet while they’re at it? Glee!
–
While it’s nice that people are trying to come up with tires that have LRR and are thus more economical, mandating that tires have LRR doesn’t make sense from a safety standpoint. Cars should come with the tires they need to handle their power and mass… allowing them to accelerate and brake easily and to corner without drama.
If we have manufacturers using weaker brake pads just to avoid the dreaded “brake dust problem” identified by CR… and then using LRR tires to promote their green-ness… we’re going to have a lot of safety-compromised cars on the road. It’s not something you can’t drive around… but most consumers can’t drive in the first place…
TTACfan
Two of my Prius-driving friends complained that Prius suffers from the cross winds on one particlar bridge in the Cleveland area. I have strong suspicion that it is, at least in part, due to the low rolling resistance tires.
Very interesting. Does anyone know if they’re sticking overly slippery tires on Priuses to up the gas mileage? If they are, I need to tell my brother to be careful. Of course, he’s not exactly an enthusiastic driver, so it might not be a problem.
Most hybrids, including all generations of Prius, have low-rolling resistance tires.