Size of the tire - are smaller (narrower) tires really better?

[CapriRacer]

Originally Posted by Old Tele man

Quoted from the last paragraph on page 39 (red color emphasis, mine):

"The lack of quality linear correlations between rolling

resistances and the basic parameters investigated suggested
that if the researcher is investigating manufacturer/tire design
differences within a tire size, other more complex aspects of

the tire will need to be considered."

And expanding on what Old Tele Man wrote, here's the quotes before that:

"Linear correlation studies of rolling resistances with the basic parameters of tire weight, over all diameter, tread depth, and UTQG treadwear rating did not
generate correlations that could be considered to represent useful tools to the consumer for predicting rolling resistance qualities of tires.

After subdividing into speed rating subcategories, linear correlation studies again failed to generate useful tools for predicting rolling resistances from the parameters measured. "

In other words, they could not find anything that was a good predictor for RR.

[CargoBoatTails]

Just makes me wonder what drag racing would be like if they had all these stupid arguments. The stopwatch doesnt lie. 65-55 in neutral deceleration times is all you need for the bottom line.

Cmon in 94 Geo put a 1.6L 5sp in the Prizm and the Tracker. The Tracker was lighter at 2189 lbs and had bigger tires, but guess what, didnt get the Prizms city mpg.

[niky]

Concrete data is concrete data. MetroMPG's rolling tests are going to be a heck of a lot more reliable than ones done at speed on the highway, where numerous extraneous factors like buffeting, wind direction and slope are harder to control. And lab tests are even more reliable, still.

-

Prizm versus Tracker: The Prizm is basically a Toyota Corolla. The Tracker is a Suzuki Vitara, which had much worse aerodynamics and a completely different engine and drivetrain package with much higher driveline losses. Hell, rear-drive Suzukis with that motor barely put out 60 horses to the wheels. (Had one on the dyno for a turbo install before)

Suzuki's 1.6 SOHC is nowhere near being in the same league as the Toyota 4AFE, whatever application it was used in.

Don't see how that's a valid comparison at all.

Unlike the Fiestas, which you yourself provided, and which returned increasingly higher EPA numbers for the variants with taller and taller tires...

[CargoBoatTails]

FX35 and G35, same engine and platform, no brainer. The clock rules all the variables, just watch any racing.

[2000mc]

Originally Posted by CargoBoatTails

FX35 and G35, same engine and platform, no brainer. The clock rules all the variables, just watch any racing.

Are you saying the g35 is faster than a fx35, because it has smaller tires, not because it's more than 600lbs lighter, lower cd, and smaller frontal area?

[CargoBoatTails]

Originally Posted by 2000mc

Are you saying the g35 is faster than a fx35, because it has smaller tires, not because it's more than 600lbs lighter, lower cd, and smaller frontal area?

We're talking city mpg here at under 20mph avg, the fx35 with bigger tires loses, pobably even if the G35 had 3 200lb passenger if not the same, which shows no vast improvement for bigger tires city driving.

[mcrews]

one word...."gearing"

[mcrews]

Originally Posted by CargoBoatTails

We're talking city mpg here at under 20mph avg, the fx35 with bigger tires loses, pobably even if the G35 had 3 200lb passenger if not the same, which shows no vast improvement for bigger tires city driving.

Actually, that is NOT what we are talking about......

We are talking about cruising at highway speed.

[California98Civic]

I don't know if this test has been mentioned here yet, but it was a good one, results in post #56:
http://ecomodder.com/forum/showthrea...tml#post246084

[niky]

Originally Posted by CargoBoatTails

FX35 and G35, same engine and platform, no brainer. The clock rules all the variables, just watch any racing.

You've already done the apple-to-apple comparison, why persist in bringing up apples to watermelons?

http://forums.nicoclub.com/g35-speci...ns-t83021.html
2011 Infiniti FX35 AWD specifications, information, data, photos 268961
http://www.fueleconomy.gov/feg/Find....n=sbs&id=19063

2003 G35 Sedan - RWD, 5AT
0.29 cd
3,369 lbs
18/26 mpg EPA

2003 FX35 - RWD, 5AT
0.35 cd - 20.7% more drag (and if you count frontal area, it gets worse)
4,045 lbs - 20.1% more weight
15/22 mpg EPA - 20% worse city economy / 18.2% worse highway economy

Any guesses as to why the FX35 uses more gas...?

It's certainly not the longer final drive ratio... ...that longer final drive and taller tires help it not suffer as much penalty on the highway as in the city.

No one here is denying a heavier wheel package is worse for economy. But a shorter wheel is worse for economy, all other factors being relatively constant. Want an example, look at other examples like the Fiesta SFE... same car, same engine and transmission, different wheels.

You want them tall and light. There's obviously always going to be wheels that are too tall, but in general, this is true.

EDIT:
As so:

http://media.gm.com/media/us/en/chev...=1407377391977

2012 CHEVROLET CRUZE SPECIFICATIONS

Tires:
16-inch: 215/60R16 ALS (26.2" tall)
17-inch: 215/55R17 ALS (Eco) (26.3" tall - tallest)
17-inch: 225/50R17 ALS (25.9" tall)
18-inch: 225/45R18 ALS (26" tall)