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Old 01-30-2010, 06:05 PM   #1 (permalink)
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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"

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Old 01-30-2010, 08:51 PM   #2 (permalink)
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...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

Last edited by gone-ot; 01-30-2010 at 09:18 PM..
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Old 01-30-2010, 08:53 PM   #3 (permalink)
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...and Appendix A of this British bicycle-tyres paper has all the equations:

http://www.legslarry.beerdrinkers.co..._Tyres_TRS.pdf
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Old 01-30-2010, 09:00 PM   #4 (permalink)
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...and here's what the "new" DOT tire labelling will supposedly look like:

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Old 01-30-2010, 11:27 PM   #5 (permalink)
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No overinflation recommendations from the manufacturer?

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

RH77
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Old 01-30-2010, 11:50 PM   #6 (permalink)
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the tire racks on road testing of several prius , found up to 4 mpg difference between tires tested, all lrr.
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Old 01-31-2010, 12:06 AM   #7 (permalink)
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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.
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Old 01-31-2010, 04:28 AM   #8 (permalink)
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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.
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Old 02-01-2010, 03:06 PM   #9 (permalink)
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...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.
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Old 02-02-2010, 10:33 PM   #10 (permalink)
ecomonkey
 
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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.

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