List of Coefficient of Rolling Friction for name brand tires??? 1

[gpara]

I am having a hard time finding any information on the rolling resistance of car tires. I am working toward increased fuel economy but the manufacturers will not answer the questions I am asking, namely what is the CRF (coefficient of Rolling resistance) of certain size tires they manufacture, Anybody have access to test data for car tires???
Gary M&G Engineering

 

[jadcock]

Gary, the only thing I can point you to is Consumer Reports' recent (11/05) test of 18 all season passenger car tires. They ran the tires on dynamometers to determine the amount of drag each tire produced. They then grouped them in broad categories of "Excellent" (5 out of 5) to "Poor" (1 out of 5), so there could certainly be statistical variations within each of those rankings. CR has also included the "Rolling Resistance" ranking on a few of their more recent tire tests in the last few years.

They may be able to provide specific numbers if contacted directly, I don't know.

Hope this helps.

Jason

 

[gpara]

Jadcock, thanks for the heads up, I checked it out and though it did not give specific numbers, it did list which tires were better in rolling resistance than others tested,my new tires are on the way, it will be interesting to see if they make a significant difference in fuel economy.
gpara

 

[CapriRacer]

If all you were interested in was whether there will be a significant difference in fuel economy, the perhaps this info will help.

It's been estimated that tires contribute about 17% to the fuel consumption of a vehicle. That means if the rolling resistance changes by 20% (which is a huge improvement!), then this results in a 3.4% change in fuel economy. In a 30 mpg vehicle this would be 1 mpg. I don't think this is significant especially considering that inflation pressure can have the same effect.

 

[GregLocock]

Hmmmmmm

Typical rolling resistance for car tires varies from 0.0110 to 0.0150, on smooth road, and truck tire might be as low as 0.006, and I have seen experimental tires as low as 0.0025. A good bicycle tire might be around 0.0055 .

So a 20% change is not all that difficult to get. Your 17% sounds about right.

When we specify tires we do include rolling resistance, it does make a measurable difference to fuel economy.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[CapriRacer]

Comparing truck tires and bicycle tires to car tires is like...ah... comparing trucks and bicycles to cars. Clearly the design goals would be completely different. FWIW, both truck tires and bicycle tires use much higher inflation pressures than car tires. (not to mention the ride qualities you get with those inflation pressures)

If the range for car tires is 0.110 to 0.150, then that's a bit over 30%, but I'll bet that includes tires that have different design goals - traction vs rolling resistance vs wear. Perhaps some speed rating differences, too. If you compared similar tires, I think you'll find the differences aren't that great, especially compared to the difference you can get with inflation on the same tire.

 

[patprimmer]

On economy rallies, we used to use the narrowest possible Michelin X tyres on the widest rims suitable for them, then pump them up to 60 psi. I know, that is over their legal inflation pressure, but it sure reduced the rolling resistance. We never did have one blow out, but we did wear the centres out rather more than the shoulders, even when mounted on relatively wide rims for the tyre size.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[GregLocock]

There's a tradeoff with high pressures. Michelin sent me some data showing that for a given road and suspension there is actually a sweet spot - too high a pressure and you start to transmit too much high frequency intot he shock absorber, where it will cause drag.

Admittedly I think this is more of an 80 psi problem than 40, but it is something to think about.

According to another piece of paper, increasing the tire pressure by 10% should reduce the rolling resistance by 6%

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[GregLocock]

http://www.greenseal.org/recommenda...ance.pdf#search='low rolling resistance tire'

has some interesting data. size for size there is much more than 20% difference between tires.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[CapriRacer]

Be careful analyzing the data from Green Seal - it's an apples to oranges comparison with some bananas thrown in for good measure.

But if you look carefully you'll see that only the 185/70R14 size has data outside the 20% range and the only tire in that size outside the 20% range is the Bridgestone B381, which I believe is the tire on the Prius (a hybrid) and there seems to be universal agreement that the tire delivers good fuel economy, but is FAR from acceptable for traction and wear.

 

[gpara]

Thanks for the ideas guys, already saw the greenseal graph, too few tire moodels tested. I oppted for the Falkin tires listed in consumer report as low rolling resistance/excellent tracktion ect. After I break in the tires i will post any difference I find in the mileage/ coasting ability versus the Bridgestone OEM tire. So far improved ride and cornering, no noticable change in sound or noise level, very agressive tread design, but still quiet. These are uni-directional tires with large arrow on sidewall for the direction of rotation. For $48.00 each versus $85-120 for recognized brand names, I am well impessed so far even if the economy stays the same. More data later. BTW test car is a 2005 Chevy Malibu 3.5L, currently on many runs on expressway 40+ mpg, actual and information center mileage checked,never thought that I would see a V-6 get over 40mpg.

 

[PaulSS]

Any results yet from your testing?

I did a fuel economy exercise in the early 80's. Part of this project included tires. I originally had a set of Goodyear belted (non-radial) snow tires (4) on a truck and after switching to a set of Goodyear Tiempo radials, I saw no significant difference in MPG. That surprised me with all the hype on radial tire fuel efficiency. I used a Zemco computer to measure data.

PS

 

[gpara]

Rolling resistance on recommended Consumer report tires.
I have finally broken in the Falken ZE 512 tires, about 5000 miles on them. Unfortunately they have NOT given me any more fuel economy than the original OEM tires. They were Bridgestone B450, SR rated, just a cheap OEM tire.
These new tires are directional in rotation and have a max tire pressure of 55psi. I have been running them at 48psi and there is no noticeble difference in coasting or fuel economy.I have checked it under varing conditions, I am disappointed that there was NO difference. Any commens????
PS I am waiting for Hydrogen generator, electrolisys, that will produce 1L./minute at 15amps, that should really boost the economy.
Gary

 

[Fabrico]

With most tires, the older they get the stiffer or harder they get. That's why new tires are gripier, smoother, and quieter. Even if you put back the exact same make and model tire, but new, you would likely be similarly disappointed in mileage. Time to move on to hydrogen.

 

[GregLocock]

gpara, american OEM tires are very likely to be optimised for fuel economy already.

Unfortunately, if you walk into a tire store and buy the 'same' tire, you may not get the same tire.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[CapriRacer]

There are a couple of tidbits that folks need to remember when it comes to measuring the tire's effect on fuel economy.

A tire's rolling resistance changes as the tread wears away. A better way to look at this is that tire weight - especially tread weight - adversely affects rolling resistance. So a brand new tire will consume more fuel than the same tire when the tread is nearly worn out.

So comparing 2 tires on a vehicle - one new, one worn - doesn't tell you much about the difference in the tires.

Also, inflation pressure has more of an effect on rolling resistance that the difference between tires. So if one is interested in reducing costs, one is probably further ahead getting a long wearing, but high rolling resistance tire and using more inflation pressure. The downside to this is that there will probably be some reduction in dry grip (and under certain circumstances, wet grip, too!)

Hope this helps

 

[tireman9]

Since some of the comments go to fuel economy you might be interested in a recent test I ran.

2006 Hyundai Tiburon V6 with Firestone Wide Oval performance tires 215/45R17 87W with 4000 miles wear 30.0 psi cold.

Warm up 3 miles. Ambient 86°F Cruse control speed set at 63.4 mph checked with Garmin GPS.
Fill gas tank using slowest fill speed and automatic shut off. Gallons measured to 0.001 Gal
54 mile loop on Interstate 76 East of Akron
Refill gas using same pump, same procedure for shutoff etc.

Test A 34.45 mpg Windows open no AC
Test B 32.93 mpg Windows closes AC on ~ 5% worse



37 yrs Tire Eng. Designed basic rain Firestone for CART. SCCA & IMSA Pro & Am. Set lap records at 6 different road courses in '89-91.

 

[gpara]

Thanks for the data tireman9 sounds like you need the scanII device that I am using to track any change in the fuel economy during testing. It was about $170.00 and has been very accurate on 2 different cars that I have had it on over long hauls and several tanks of gas. If there is a difference it will show up immediately on the averagempg and I use it to keep the loads constant, it gives road speed, engine rpm, tps, engine temp ect in blocks of 4 readouts at a time. I contaced the company to find out how they were calculating instant mpg but they said it was one of their secrets and proprittary informattion from there device
Gary