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Old 12-05-2007, 03:36 AM   This thread is in the EcoModder Project Library | #1 (permalink)
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Arrow Video: Can Skinnier Tires Increase Fuel Economy?

I remember back when I used to ride a bicycle (man that was YEARS ago; that's got to change) I noticed that the mountain bikes felt like they had more rolling resistance than the cruisning bikes with their skinny tires. This made me wonder if getting skinny 'donut' tires on my car would increase fuel economy.

I purposefully put the smaller tires on the rear so that my speedometer and gearing would remain the same as with the larger tires.

These are the documented results:


I should add that I don't use these tires on a regular basis because of their lack of traction, ride quality, and quietness.

Feel free to discuss.

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Old 03-27-2008, 12:42 PM   #2 (permalink)
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I'm surprised this hasn't been discussed here yet. I've thought of going with a more narrow lighter rim/tire combo for the rear. Impressive gains with a small change shown in the video.
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Old 03-27-2008, 12:54 PM   #3 (permalink)
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I don't know if a thread has been put up on the topic yet, but I know people have recommended them before. I don't remember if it was on GS or here, but someone put extremely skinny tires on their vx. 155/85/13 if I remember correctly.

Ofcourse you lose traction/stopping ability, though. I think a bigger question is what is a better choice: a wider LRR tire or a skinnier normal tire?

Good work, though.

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Old 03-27-2008, 01:01 PM   #4 (permalink)
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a timely topic - i was just looking for other wheels and tires for the rear of the altima as well. Equipt with 205/60 -15's. pondering going to a 175/55 - 17's so in can fit them under a cover in the rear and moon disks up front ( although i have only seen up to 16 for moon disks .

Would love to see data on LRR vs skinny tire. anyone have comparison?

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Old 03-27-2008, 01:03 PM   #5 (permalink)
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?"Your Guess is as Good as Mine"?

I would believe that rolling resistance plays a part in the reduction factor,
BUT,
Don't discount the aerodynamics of the two tire styles.
OEM = taller, wider, more contact patch
Donut = shorter [slightly], narrower, less contact patch, and they present a round face to the wind.
OEM tires present a large flat face to the wind.
many variables in one component.
changing all those variables at once = big difference.
I have found a source fro 145 80R 13 tires.
when my current tires are worn out I will replace them with the 13's
Your video just pushed me over my decision hump. I was waffling because this change requires the purchase of new rims also.
But I haven't been to the bone yard in a while, they probly miss me.
Schultz
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Old 03-27-2008, 03:44 PM   #6 (permalink)
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SPOILER ALERT:

Peakster'll probably be mad at me for posting the results here in the thread, but here's what he observed in an A-B-A test, with a pair of donuts (on the rear) for the B test:

A - 55.9 mpg (US) average (regular tires)
B - 60.9 mpg (US) average (donut tires)
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Old 03-28-2008, 02:05 AM   #7 (permalink)
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I'm looking at narrower but heavier and taller tires.

Current tires are 235/70R16s which are 29.1" tall and 32 pounds rated at 44 psi and driven at 55 psi.

I'm looking at replacing them with 215/85R16s. They tend to run around 30.4", 0.7" taller and about 4% more gearing which should nullify the speedo error. Nearly all models are heavier. Some as much 47-48 pounds. The weight wouldn't help in the city stuff. Rotational mass is the bane of all cyclists.

The D rated tires in this size are rated to 65 psi and the E rated tires 80 psi. It would be nice to get rolling resistance and noise specs...

Think they'd help? The aero could get worse from the vehicle being even taller. The gearing change should be minimal but help on the hwy unless lost to aero. They take mega PSI...
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Old 03-29-2008, 08:20 PM   #8 (permalink)
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No opinions?
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Old 03-29-2008, 09:03 PM   #9 (permalink)
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Who - re. tire size change.

Take a step back - you mentioned speedo error. Do you have an error now and the taller tire should correct it? That would be nice.

Some thoughts re the tradeoffs with the larger tire:

It's taller so raises car so aero gets worse.
But remember, .7 inch bigger diam. means the car will be .35 inch higher. Yes, .35 inch raise is not ideal but maybe not as significant as the other gains you'll get.

Tire is heavier:

I think the large weight increase will hurt you. But read on, I think there's hope...
A larger tire will be heavier but if tire is taller and also skinnier I don't think it has to be that much heavier than your stock tire, and maybe not heavier at all.

What I'm getting at is I think the tire(s) you've found are rated for a much higher load capacity and so are built with a lot more beef. Probably pricier too. If you find tires with similar load rating and spec'd for 44 psi they'll likely weigh similar to what you have now. You can still run the 44 psi tires at 50-55. If you want more, maybe go to a tire rated at 52 to 55 psi and I'd think you can run it at 60-65-70 psi without worry, if you can stand the hard ride.

Oops - I just noticed you're driving a Santa Fe. Anyway, do look up the orig spec tire and its load rating. No need to get a tire built to carry 50% more weight than OEM spec unless that's how you load up your vehicle.
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Old 03-29-2008, 09:38 PM   #10 (permalink)
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This is probably a totally dangerous/unfeasable option, but I was at the Lowes the other day and walked past their trailer tires. 12" just like the metro, but skinny, and a VERY high psi rating. ??? ummm...to bad they were a 5 lug.

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