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Question
If i change my tire from P265/70R15( Nissan spec) to P235/75R15 for my 1997 Nissan pathfinder se. would there be a problem on my gas mileage?

Answer
Earlwin,

First, you do NOT want to go down in load index.  That is the direction towards increasing tire failure risk.

Second, it is also the direction towards worse fuel economy.  Not only is it about 3% smaller in diameter, but the rolling resistance would also change an additional 5% - for a total of an 8% loss.

So overall, this sounds like a bad idea.

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Barry Smith

Expertise

I have over 30 years experience in the design, manufacturing, and testing of tires. I have served as the technical advisor to the "800" number. I have authored or co-authored many publications - usually without credit. I can answer almost any technical question, but please don`t ask me to compare brands. I probably have prejudices because of my work experience.

Experience

Member SAE (Society of Automotive Engineers) Member Tire Society (Tire Technical Organization) SCCA Regional Competiton License holder Authored many training manuals on tires, their care and use.

Organizations
SAE (Society of Automotive Engineers) SCCA (Sports Car Club of America) Tire Society

Publications
You may want to visit my web site: http://www.barrystiretech.com/index.html

Education/Credentials
I am a graduate of the University of Dayton, Dayton, OH - BME, 1971 I attended graduate school at the University of Akron - but did not complete my PhD - something I regret.

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