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Fuel economy change with tire size change?

 
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Old 07 Aug 2011, 05:09 pm
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Question Fuel economy change with tire size change?

This is something I've been wondering about for a while...

Stock tire size for the PT Cruiser (at least 2007) is 195/65R15. At 120km/h my engine revs around 3000 RPM.

If I went with a tire that was 10% larger, say 225/60R17, my engine would rev 10% slower at the same speed. So when I was doing 120km/h then engine would be revving around 2700 RPM and the speedometer would read around 108km/h.

Does that sound right?

My PT starts up off the line pretty quickly, put I find the engine revs too high on the highway. If I go to a bigger tire, I will lose some of the torque off the line, but the engine should rev lower on the highway. Hopefully the lower RPMs would save me some gas.

Does this sound at all reasonable?
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Old 07 Aug 2011, 06:14 pm
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Default Re: Fuel economy change with tire size change?

well there is something about the revolutions of the tire. The bigger the tire the longer it takes to turn. Honestly i can't remember what this has to do it but i know there is a difference.
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Old 07 Aug 2011, 06:16 pm
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Default Re: Fuel economy change with tire size change?

i got this from yahoo! answers http://answers.yahoo.com/question/in...6105251AA0k94i

"Larger diameter wheels certainly won't help because you will end up with heavier wheels and tires that take more power to turn, and wider tires that increase rolling resistance."
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Old 09 Aug 2011, 04:01 pm
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Default Re: Fuel economy change with tire size change?

Larger tires will be heavier... but since I'd also be replacing the wheels, I could find lighter wheels than I have now.

...I'm thinking of getting larger wheels, so I'm trying to take other changes into consideration at the same time.


And my stock wheels are actually 205/55R16
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Old 09 Aug 2011, 04:08 pm
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Default Re: Fuel economy change with tire size change?

Skinnier tires - width of tread - give better mileage because of less rolling resistance. You trade some handling in corners, but get a better ride (more rubber between road and rim) and they are better in the snow. Also, 15 & 16" tires are usually more abundant and cheaper.
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Old 09 Aug 2011, 05:45 pm
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Default Re: Fuel economy change with tire size change?

i went up a bunch od sizes on my 4x4-----(256-?-16 to a 36x12.5x17) and went from getting 18mpg to 14 and all that changed was the tires and wheels

on the PT i went to a 16 wheel and tire and there was NO diffrence at all
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Old 11 Aug 2011, 05:33 pm
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Default Re: Fuel economy change with tire size change?

Have you ever seen those high mileage test cars in magazines or on TV. You will notice that they all have very skinny tires. The more tread on the road the worse the mileage. Bigger wheels will help for sure. So the ideal setup would be a 26" bicycle tire and wheel Somehow I don't think that will work! You have to realize that the manufacture takes into consideration; weight of car, load on tires, tire sizes, etc. to come up with what they think is the right size tire and wheel size. Any changes you make will alter the speedo as well. Summer tires are usually much better for fuel mileage then M & S tires. Which great for me in Phoenix Arizona, but I live in a rare area of the country. My suggestion leave them alone!
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Old 11 Aug 2011, 06:24 pm
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Default Re: Fuel economy change with tire size change?

Don't think the results will be worth it especially with the added cost of tires and rims. Just driving prudently will do a world of difference for your mpg.
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