LRR (low rolling resistance) tires - Green Seal report & list

[Vekke]

http://www-nrd.nhtsa.dot.gov/pdf/esv/esv21/09-0300.pdf

Here is some test data on Rolling resistance. I understand that best low rolling resistance tires in that test are:
goodyear integrity and bridgestone potenze RE92 owl?

[CapriRacer]

I find it interesting that the rank order changed slightly depending on which test was run.

I also find it interesting that the Goodyear Integrity and Cooper Discoverer ST-C were tested in 3 different sizes - and that the RRF values were different enough that one of the 3 was in a different grouping.

[Vekke]

I have always tought that tire companies do almost all the R&D work on popular sizes. Then they will just scale it down to other sizes and widths and say that they are the same. Maybe that test proves my estimations true?

[CapriRacer]

Originally Posted by Vekke

I have always thought that tire companies do almost all the R&D work on popular sizes. Then they will just scale it down to other sizes and widths and say that they are the same. Maybe that test proves my estimations true?

While I can confirm that tire manufacturers develop tires in a couple of sizes, then scale them up and down as appropriate, I think what the test says is that there is something else going on and you can't compare the rolling resistance of tires of different sizes.

I'm surprised no one has posted this in this thread:

http://www.energy.ca.gov/transportat...%20Testing.pdf

It's a study done for the California Energy Commission. Not only does it test various tires for rolling resistance, it also studies the effect tire size has on rolling resistance. This confirms that different sizes of otherwise identical tires have different values - enough that you can't reliably compare tires of different sizes.

I ran a regression analysis on the data and developed an equation so the differences in tire size could be compared, but the R-squared value wasn't all that great: 66%

[Vekke]

Originally Posted by CapriRacer

While I can confirm that tire manufacturers develop tires in a couple of sizes, then scale them up and down as appropriate, I think what the test says is that there is something else going on and you can't compare the rolling resistance of tires of different sizes.

Yes I also meant that popular sizes. Usually this means tires that are normally used as factory size tires on cars. There 3-5 popular sizes on different size cars. Other sizes are then scaled like you confirmed. This gived me a nice idea and lets see how things start to develop.

That report was superb. If you have more similar "open" reports on your sleeve please post .

[CapriRacer]

Originally Posted by Vekke

Yes I also meant that popular sizes. Usually this means tires that are normally used as factory size tires on cars. There 3-5 popular sizes on different size cars. Other sizes are then scaled like you confirmed...............

I know that in some places in Europe, only tires approved by the vehicle manufacturer are allowed to be applied - even as replacements.

That is definitely not true in the US. There are whole lines of tires - 30 to 40 different sizes, that are designed off a couple of prototypes - and that was what I was referring to.

- AND -

It is pretty universal that any OE tire is unique to itself. The vehicle manufacturer decides what the performance specs are supposed to be, and the tire manufacturer complies. If the tire manufacturer refuses to go along, te vehicle manufacturer will find some tire manufacturer who will.

[JMac]

I think what the test says is that there is something else going on and you can't compare the rolling resistance of tires of different sizes.

I believe I've been able to identify at least one of those variables which change in a non-scalar way when tires are scaled up or down for size. For example, the legendary Bridgestone B381 185/70-14 tires have a 5.0" tread width, while the 185/65-14 version of the same tire has a 5.4" tread width. If my math is correct, that's an 8% increase in tread width, which would increase the size of the contact patch and also increase rolling resistance.

While looking at other tires, it seems the tread width of the same tire between different sizes goes up or down almost arbitrarily depending on the brand.

Tirerack is pretty good about giving detailed specs about tires.

JMac

[mwebb]

the contact patch size does not change
if tire pressure remains constant

contact patch SHAPE changes with differing size / profile of tire , contact patch area / size remains constant

[CapriRacer]

Originally Posted by mwebb

the contact patch size does not change
if tire pressure remains constant

contact patch SHAPE changes with differing size / profile of tire , contact patch area / size remains constant [/COLOR]

Sorry, but that is an old wive's tale:

Fact or Fiction? Tire contact patch and air pressure.

If you want to assume that for the purposes of analysis, go ahead. Just be sure you don't draw any conclusions where that is a vital piece.

[rmay635703]

Originally Posted by MetroMPG

With California's July '08 implementation of LRR labeling & standards, I'd expect it's going to get easier for the public to get info & make judgements than it has been.

My car's tires are more likely to dry rot off the rims before I ever wear them out, so eventually I'll have to shop for replacements too :P

Sorry to dredge up an old thread, but beyond tire retailers saying whether a tire is considered LRR or not, has that law actually done anything?

I can find no rating data on LRR tires and am strongly considered Bridgestone Ecopia ep422 PLUS's for the volts front tires (don't ask) over the stock crapola

But I have no idea what tire is the most efficient in the goofy 215/17's that are on the car.

Some folks claim an extra 6 miles range using the ep422 plus (not the regular non plus version) over stock but there is nothing to support or validate that claim.

Ah well. I am told the euro specs should not be used to compare the same brand tires here because the same model of tire can be different in our country as compared to europe, ah well.