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Car Forum / Chevrolet / Chevrolet Trucks / August 2008Tire size vs. gas mileage
I've seen both sides of this argument, but am interested in what folks here might have to say on the topic. I've got a 2003 Silverado. Stock tire size is 245/75/16. If I go to a 265/75/16, the tire diameter increases by about an inch giving me about 3% less revolutions per mile. On the surface, this would give me 3% more mileage - BUT - how does the increased friction from the additional tire width and the theoretical increased work the engine must do play into the equation? 2nd scenario: I can go to a 265/70/16 and have virtually the same diameter with 20mm more width. How would this factor alone affect mileage? I think you would have to do some pretty tight measuring to really see a difference in your mileage. It would LOOK a lot nicer with the bigger tires. I did it to my 97 Yukon and was pleased with the new look, and they didn't rub anyplace. Regards, JR > I've seen both sides of this argument, but am interested in what > folks here might have to say on the topic. I've got a 2003 [quoted text clipped - 8 lines] > diameter with 20mm more width. How would this factor alone affect > mileage? tire size has nothing to do with gas mileage >tire size has nothing to do with gas mileage How can it not? If a tire has a (extreme example) 30% larger diameter, it's going to travel further given the same amount of engine RPMs. At some point there has to be diminishing returns due to more effort being required. My question has to do with where that point is reached. "scrape" <scrapeNOTHANKS@earthlink.net> wrote in message > How can it not? basic physics.........you could run bicycle tires (if it were possible for them to support the vehicle weight) and the vehicle would get the same gas mileage I think you need to re-think that, if you loose 5 pounds of air in your tires, you make the tire smaller, and thus will make your milage go down. What changing tire sizes does, it will make your speedomter off, so you may get a ticket, now that will cost you some money. > "scrape" <scrapeNOTHANKS@earthlink.net> wrote in message > How can it not? > > basic physics.........you could run bicycle tires (if it were possible for > them to support the vehicle weight) and the vehicle would get the same gas > mileage > I think you need to re-think that, if you loose 5 pounds of air in your > tires, you make the tire smaller, and thus will make your milage go down. Yeah, but I wasn't talking about "drag". I was talking about tire size. >> I think you need to re-think that, if you loose 5 pounds of air in your >> tires, you make the tire smaller, and thus will make your milage go down. > > Yeah, but I wasn't talking about "drag". I was talking about tire size. A larger diameter tire has the effect of reducing the effective rear-end ratio. There is a well-known relationship between rear-end ratio and gas mileage. I expect that a 3% change in rear-end ratio would have a small impact on gas mileage - and a 3% change in tire diameter should have the same impact. --Steve >>> I think you need to re-think that, if you loose 5 pounds of air in your >>> tires, you make the tire smaller, and thus will make your milage go down. [quoted text clipped - 6 lines] >small impact on gas mileage - and a 3% change in tire diameter should >have the same impact. Would, however a slightly fatter tire negate that difference due to additional drag? There has to be a "sweet spot" somewhere. >I think you need to re-think that, if you loose 5 pounds of air in your >tires, you make the tire smaller, and thus will make your milage go down. [quoted text clipped - 8 lines] >> gas >> mileage No it wouldn't. It would get better mileage . The tire would have to be super hard and the contact patch would be super small. Also air resistance would be much reduced. But don't try and turn it fast. It will slide . That's why all high mileage experimental electric, or other vehicles have skinny tires. Less rolling resistance. Any wider tire will get worse mileage if everything else stays the same. More road resistance and air resistance. If you could mount a razor blade ring on a wheel . And it could support the weight and the road could take it. It would get better mileage then a bicycle tire. >"scrape" <scrapeNOTHANKS@earthlink.net> wrote in message > How can it not? > >basic physics.........you could run bicycle tires (if it were possible for >them to support the vehicle weight) and the vehicle would get the same gas >mileage I think you're assuming that the engine is doing the same work and this may be the case if the final gearing is changed to give the same ratio based on a different diameter tire, but a larger tire is going to go further given the same number of engine revolutions. The engine may burn the same amount of fuel running at 2500 RPMs for one hour regardless of tire size, but the vehicle would have traveled a greater distance. MPG would increase. Basic math. > "scrape" <scrapeNOTHANKS@earthlink.net> wrote in message > How can it not? > > basic physics.........you could run bicycle tires (if it were possible for > them to support the vehicle weight) and the vehicle would get the same gas > mileage Only if the tire was the same diameter as the old one. Also the thinner tire would get better mileage due to the reduction in surface friction. Has been proven many times. It is FAR more than basic physics.  SignatureSteve W. Near Cooperstown, New York about 30 miles west of Cleveland is that point. More seriously, I don't know. SignatureChristopher A. Young Learn more about Jesus www.lds.org . How can it not? If a tire has a (extreme example) 30% larger diameter, it's going to travel further given the same amount of engine RPMs. At some point there has to be diminishing returns due to more effort being required. My question has to do with where that point is reached. Size matters. Especially to woman drivers. SignatureChristopher A. Young Learn more about Jesus www.lds.org . tire size has nothing to do with gas mileage > Size matters. Especially to woman drivers. > > tire size has nothing to do with gas mileage I was under the impression for a long time that taller, skinnier tires offered better gas mileage. Due too less rolling resistance , as the contact patch is smaller. and less air resistance. And they travel farther for the same amount of revolutions. They also get better traction in the snow. And those type of tires ( Old folgy tires) generally have a harder rubber compound that creates less friction too. Then wider lower aspect sporty tires. They are also cheaper to buy. That's my story and I,m sticking to it. |
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