Bridgestone Tires and LRR
 

This is the response I got from Bridgestone concerning LRR tires:

"Thank you for your inquiry, LRR means low rolling resistance generally associated with tires. Most consumers associate LRR in reference to fuel economy. Rolling Resistance information is not available as measuring would need your exact vehicle along with exact road you are driving on. Rolling resistance is measured by road service ambient temperatures, tire pressure, tire foot print, weight of vehicle on tires, the suspension, and so much more. There can be two different rolling resistance numbers depending on what road you are driving on. Every vehicle in combination with tires and the road driven on will vary in rolling resistance. This means that in order to calculate your rolling resistance we would need to test your vehicle with whatever tires you have on it, and on the exact road you drive on.

I want to clarify if you are actually looking for rolling resistance information as a means to better your fuel economy. If this is the case, MPG and rolling resistance are two completely different things. Rolling resistance is such a small factor of the overall fuel economy. A decrease of 10% in rolling resistance only gives you 1-2% increase in fuel economy. This is extremely minuscule.

There are 3 things that make up fuel economy. 1) Tires 2) Aero Dynamics 3) Engine torch. So tires make up only 1/3 of the overall fuel economy with only 10-15% of that 1/3 being rolling resistance. The best ways to increase MPG/Fuel economy is not worrying about rolling resistance; it is focusing on the information below.

The weight of the tire will have some affect on gas mileage. What is more of a factor, though, is the tire "footprint". This term refers to the actual area where the "rubber meets the road". The same size tires may have different contact areas and therefore different gas mileage implications. More rubber coming in contact with the road can create increased rolling resistance. Generally, narrower, taller tires are better for fuel economy, if you retain your current wheels. Increasing the tire aspect ratio, for instance from 70 to 75, will provide additional load carrying capacity.

But what makes a difference is to monitor your tire inflation pressure frequently. Checking once a month will assure you are running that pressure recommended by your vehicle manufacturer and provide the best fuel economy. Tires will naturally lose air pressure, like a balloon, and the loss of just 7 psi can lose you 2 mpg.

Thank you.

Rod Manibo
Merchandising & Inventory Management
Bridgestone Retail Operations, LLC"

...here's a Dutch paper on LRR and CRR:

http://www.iea.org/work/2005/EnerEff...vers_paper.pdf

...and here's the power-point version:

http://www.iea.org/work/2005/EnerEffTyre/glaeser.pdf

...and Appendix A of this British bicycle-tyres paper has all the equations:

http://www.legslarry.beerdrinkers.co..._Tyres_TRS.pdf

...and here's what the "new" DOT tire labelling will supposedly look like:

http://cdn-www.greencar.com/images/l....php/label.jpg

No overinflation recommendations from the manufacturer? :p

Consumer Reports used to print RR values of tires in their reviews -- I wonder if they still do...

The problem currently, is that it's not a required value to test and print on the tire (if that changes, that would be a huge step in the right direction). There's an independent laboratory in Akron, Ohio that has been used to test tires for the rubber companies in that area. I remember trying to find out more beyond the "Green Seal" report a few years ago, and struck out.

Here's a good thread on the subject.

I usually try to identify OEM tires from fuel efficient vehicles, or specific tires that are marketed as LRR (like the Michelin "Green-X"-rated tires). That's what led me to Michelin MXV4-Plus XSE tires for the Integra. These are solid tires that have held 50 psi (warm weather) with no pressure-related wear and no punctures / rips for ~35K miles (around some serious potholes and lumps). But, they're not cheap and suffer some Winter traction issues requiring a drastic reduction in pressure).

By the way, I disagree with Bridgestone's underestimated effect of a tire's rolling resistance on FE. Vehicle manufacturers know the value and ensure that some vehicles trade handling and comfort for that boost in FE.

It's a big investment, to be used for quite some time -- so I respect and understand the extensive research :thumbup:

RH77

the tire racks on road testing of several prius , found up to 4 mpg difference between tires tested, all lrr.

the ecopia ep100 is second best in rr in the tire rack test,, they are also great on wet road testing anybody know how it compares to the b381 on rr? dont bother calling the tire stores they dont know 2 ot the 4 i called had'nt heard of lrr tires,,,,,,,sad.

That response is sure all over the place. He says that RR makes almost no difference to MPG (HA!) and then goes on to say that inflation pressures make a big difference in MPG.??!?

Most Nokians are LRR. I have WRG2 on my Prius and they are excellent. The i3s and the H are both LRR, the H being the lower. They use a silica/canola oil compound. The H also recently won a European auto club test. Also they are non toxic since 2004. All this and cheaper than Michelins.

They used to have an NRT2 tire with a measured RR of .0085. It came in #2 in the green seal report if I remember correctly. Don't know what their tires measure in at now but I bet they are similar. I looked at the B381 but the traction rating of B is just not good enough to justify the .0065 RR

You can get them at tire factory.

...was seeking information about possible replacements for the OEM Goodyear Eagle RS-A 205/55P16's (Crr = 0.00915) on our '09 Vibe.

...needless to say, the initial reply wasn't very helpful at all.

old tele ive been looking at rr on tires for months now, the ecopia by firestone is great in wet cornering and breaking has a extremly low rolling resistance and a 50k tread wear warrenty. they look good on paper, dont know if they have your size or not.cost is good also.

I reckon it be thread bumpin' time.
I have some cheap primewells, that were $40 when I bought them 2 years ago. The same tire is now $50, (?). Anyway, I want a SERIOUS upgrade, as I've have tread separation in one of my tires, and I got my prorated warranty a few weeks back for a new one.

I've been looking for some LLR tires, with good pricing, and it seems that the Ecopia EP100 is the best tire for the mpg, and has especially good wet traction. They are about $80 each for my tire size, but I'm willing to pay that kind of money for an upgrade from my low quality tires I have now. I deliver pizzas now, and I'm planning on going on a huge road trip this summer, so the savings will come much faster than I thought they would a few months back, when getting new tires would not have made financial sense.

I have a 94 Corolla, and my tire size is 175/65/R14.
Any other good LRR tires that would serve my needs?

The original insight came with Bridgestone Potenza Re92. That specific size is, I believe, still the lowest RR tire out there. Otherwise, I'd look at the tirerack test, or talk to basjoos who runs the same size. He gets to test a fair number of tires with the miles he puts on.

The Michelin energy saver a/s tires rated a little higher in the tire rack FE testing. The Ecopias were slightly better in traction as I recall, and also a fair amount cheaper. I just ordered the Ecopias for my Prius.

Those ecopias are doing very well for diamondlarry. He had a 121mpg segment yesterday.

Do you know what pressure he is running with the Ecopias?

Likely more than you'll want to run, lol. Last time I was in his car they were 70 psi if I recall correctly. Larry is a bit... extreme. :)

The prius tire pressure sensors light up at 70 psi and last I heard, the light was on. ;)

I'm running 60+ myself.

I comparing the Michelin Energy Saver with the Good Year Fuel Max and the General Tire Altimax.

I'm leaning towards the Michelins -- they are lower revs per mile (larger diameter) and they weigh the same (17 pounds). This seems to be the lightest for the 185 width 15" diameter tires. The Michelin tread wear rating is lower. than the Goodyear's, but similar to the General's.

The General's have higher sidewall max pressure, and better wet traction, and they cost (a lot) less.

Hmmm.

I don't think the Altimax is designed to be LRR at all. Not that its a bad tire, I just know you'd get better FE with the two others.

I have GY Assurance Fuel Max tires. There is also a "WeatherHandler Fuel Max" but it may be an exclusive for sears. The GY's are rated for 51 PSI; they didn't fee stable until I hit 67 PSI in 'em and had 1000 miles to wear off the 'newness' of the tire.

Just ordered a set of Yokohama AVID TOURING-Ss. Someone on a Prius forum I found reported an extra MPG above the OEM Integritys, and I bet they'll be MUCH better than my Wal-Mart specials Douglas XtraTrac IIs I have now.

They're also rated at 51 PSI max, much better than my current 44.

Yoko Avid's are what I am buying too...
 

I have used them before. Did 205/75-15's on a '97 Camry for approx 9.25% over size on diameter.

At a mere 40lbs they were firm enough to get 35-36 on the Camry, great wet traction, decent light snow and OK dry traction. They were quiet too.

Inflated to 50 the solid line tread down the middle of tire makes for pretty good LRR tire.

I will be doing 205/70-15, approx 6% oversize from stock 195/70-14's.

Pete

What kinds of gains did you see when you switched? My last tank (and first with the new Yokos) surprised the heck out of me, even with some full-throttle acceleration at the local drag strip. I was going to test some intake setups, but something didn't sound right on the second pass, so I called it a day. Even after all that, I got 26.4 MPG. I'm planning on reworking my front air dam to reduce the frontal area and meet with the front undertray, so that could push me above my 30MPG goal.

Nokian is about to release a new model, called the eNTYRE:

http://i560.photobucket.com/albums/s...lot/eNTyre.jpg

eNTYRE Marketing stuff:

Those are some good wear ratings. Too bad I can't get them in my size.

OK,
results from 649 mile run. 18.03 gallons for 35.8 MPG.
So far I have only installed the front 2 tires. (Yokohama Avid S 205/70-15's approx 6+% oversize.
And this trip included more local driving, 1/2 hr of stop and go interstate traffic and 1/2 hr of right or left lane closed slow downs. Its repaving season.

My RPM's are down. Now when speedo reads 65, actually like 68+ rpms are down to around 2600 instead of 2800.
It definitely took its toll on low speed(60-65) hill climbing though. At 60 rpms get down to below 2400 and it took a lot more throttle to maintain speed.
Sweet spot is at 16-17 tps(Throttle) on level grade at 65-70mph. MAP goes below 8.0, even down to high 6's to mid 7's and mpg on Scangauge hits high 30's to low 40's.
I really need to get the rear tires on, may need spacers, and get to work on aero mods to reduce HP/torque load at why speeds.

Pete

Got all 4 on now...
 

Back tires clear the bottom on the strut house by about 3/8 inch.

Tomorrow I will embark on a 500-600 mile 2 day journey to/fro work.

Will top off tank, top off tires at 44 front 40 back.

4 hrs of driving at a time I cant take too rock solid tire pressure.

http://www.tirerack.com/tires/tires....omCompare1=yes

Pete

...but what are their LRR "numbers"?

...the stock OEM Goodyear Eagle RS-A's has LRR = 0.0092 value.

...wonder how much better the Nokian EnTYRE's might be?

You mean the coefficient of rolling resistance, CRR? Most tire companies don't publish those, unfortunately.

Also, the lowest CRR I've encountered is 0.006 for Potenza RE92's, 0.0035 for race bicycle tires.

the only CRR for Nokian I have seen is for the discontinued NRT2 which was the number two tire in the green seal report @ .0085. I hope they have improved since then.

Highest on the list was .0152 and lowest was .0062 Bridgestone B381 185 70 R14

Greanseal's cutoff was .0105. I would say low would start below .009

I did read somewhere that the X-radials which are Costco's exclusive in-house tire made by Michelin are a LRR tire. I have them on the Previa and they do roll really well. I have no comparison though. They are a rib tire so that's a plus. I'm happy with them.