Does Tire Size Affect Gas Mileage? - Fuelly Forums

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Old 01-07-2008, 04:49 PM   #1
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Does Tire Size Affect Gas Mileage?

My grandfather use to drive semi-trucks, during the 50s. He was told to put on a taller tire to get better gas mileage. Do you think this would work out for a regular car now? I drive a 05 Honda Accord, that does good on gas mileage. I am thinking of replacing the tires, from size 205/60/16 to a 205/65/16. I found a Falken tire that keeps the same speed rating as the o.e. but is a little taller. Any thoughts? Thanks
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Old 01-07-2008, 05:04 PM   #2
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Pickup truck guys have beaten this horse to death.

Stay with the OEM size rubber. If you go bigger you increase the angular moment of inertia (AMI) of the tire/wheel assembly. AMI goes up with the square of the diameter.

Increasing the diameter of the wheel means your engine has to accelerate four bigger "flywheels" every time you pull away from a stop sign or light.

Believe it or not, the Honda engineers know what they are doing.
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Old 01-07-2008, 09:32 PM   #3
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Theoretically, getting a taller tire would hurt your FE if you do alot of in town driving. Like said above, you are adding more weight on all corners which strains the car more off the lights. However, a 205/60/16 and 205/65/16 are so close, the weight is almost a moot point. Both weigh 20 pounds (average, depends on composite and build)

Now, if you drive a lot on the highway, like those big rigs, it will help you alittle. A 205/60/16 has a 24.7" total diameter which equals 840 rotations per mile. A 205/65/16 has a 25.4" total diameter which equals 818 rotations per mile. That would lower the rpms on your transmission and should give a small FE gain, but probably not much at all...

But you probably do alot of stop and go, so I dont think the little fe gain would compensate the price of new tires..unless you need new ones anyways...
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Old 01-08-2008, 03:45 PM   #4
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Yeah, I guess thats why, that rule, would apply to semi trucks and not regular cars. Since a semi truck does over 95% on the highway and I do maybe 60% at most.
I was wondering this becasue I am in search of some new tires. Do you think that a certain tread pattern could hurt or help mpg? Also I run my tire presure high but can you run it to high, where it would explode the tire, haha. Ok maybe not explode but do something like that. I run my tires at about 40 p.s.i. It says on the tire that 44 p.s.i. is max but what if I run 50? Thanks
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Old 01-08-2008, 05:09 PM   #5
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I've seen 90psi in a 35psi tire, but thats just insane. 40 in a 44 is fine, 50 isnt dangerous IMO but itll be alittle bit rougher of a ride. I have 45 in 35's
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Old 01-15-2008, 11:36 PM   #6
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I have an 03 Accord, same generation as yours. I also inflate my tires to 40PSI (max cold 44). Going higher isn't going to help MPG, so why take the risk. Hondas are designed to run efficiently. Keeping your car in very good condition, doing maintenance on schedule, rotate the tires, not carrying unnecessary weight around, changing the air filter every 12-15K miles...that will give you the best MPG along with wise driving habits. I use FP60 in the duel to keep the fuel injectors clean, it's a low dose, one ounce for every 5-6 gl of fuel. We also changed spark plugs just before 40K miles.

We have the 4cyl/5AT. More than half the time we get 35+MPG on the highway; highest we've achieved was 39. Sometimes it drops to the low 30s. Fuel quality is not consistent month to month, brand to brand.
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Old 01-16-2008, 12:11 AM   #7
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Willhall45 -

I am using one size larger and my GPS shows that I am getting a +2% change in MPG :

New shoes (aka tires)
http://www.gassavers.org/showthread.php?t=3699

I chose these tires because I think they have an LRR (Low Rolling Resistance) pedigree.

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Old 01-16-2008, 01:17 PM   #8
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I am looking at replacing the 195/70R14 tires on my Camry with 185/75R14 tires when I can afford it. They're much cheaper and should offer a tiny improvement in MPG.
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Old 02-26-2008, 11:30 PM   #9
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So, if I'm understanding this correctly, you get better FE from a 14 wheel than from a 15 inch wheel?

I ask this because my zx2 is the 'sport' model, part of the package is 15" instead of 14" wheels.
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Old 02-27-2008, 08:47 AM   #10
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A 14" wheel would most likely be lighter than a 15" wheel (assuming they are both steel), but it would be a few pounds at most I would guess.

Just remember, if you get taller tires, its going to throw your gauges off a bit (speedometer, odometer, tripometer....). And that would also affect your calculations when estimating MPG's.
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