Rolling Resistance

Joined
Jan 5, 2008
Messages
3,561
Location
Central Iowa
Anyone know where I could get data on rolling resistance on car and pickup tires? It is readily available for commercial semi truck tires, but is hard to find for smaller tires.
 
Joined
May 4, 2003
Messages
6,614
Location
southeast US
The only sure way to get the LRR tire is to use OEM. Also, silica based tires tend to have lower RR, but it is hit and miss. DIY LRR tire is a tire inflated to the max pressure. Some tires (Sumimoto comes to mind) have max pressure in 50s, making them an ideal subject for overinflating.
 

TiredTrucker

Thread starter
Joined
Jan 5, 2008
Messages
3,561
Location
Central Iowa
It's too bad that it is so hard to find actual rolling resistance figures for consumer auto tires. This is open information that is easy to obtain for commercial truck tires. Even tires within the same brand with similar tread designs can fluctuate greatly on rolling resistance. IE. Bridgestone M726 tire has a rolling resistance of 155 (downright criminal if you are trying to make a buck driving a semi truck). Bridgestone M720 has a rolling resistance of 115 (much better). Yet, side by side, tire size equal, inflation pressure equal, they have virtually the same tread design. The compounds that make up the tire and some other factors play into it. Inflation pressure tolerances may mean a little, but if the side wall flex and compounds are such that it makes for a lousy rolling resistance tire, you are not getting your money's worth. I realize that this whole discussion my be arcane, but in this economy, getting the most bang for the buck is a solid idea. I just wish the tire companies would lend a hand and publish rolling resistance data for consumer tires like they do for commercial tires. Is it conspirtorical to think that maybe they don't want us to know this data since they make it virtually imposible to track down?
 
Joined
Feb 22, 2003
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4,001
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Somewhere in the US
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.)
 
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