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Tires/Tire Size


QUESTION: I have a 2010 Nissan Murano SL. I bought new tires yesterday that were rather expensive. The size tire that came with the car are P235/65R18 104T.  I wanted a specific brand tire but the one in the size for my car has bad reviews so I was going to get a different brand in that size. But, the tire store said I could get the brand I wanted in size P245/60R18  104T. So, I bought that size but they said if I don't like them I can bring the car back and get the size that Nissan had originally put on.

How much difference does the size of this new tire make compared to the original size? I've never switched tire sizes before. I'm not sure I like how the new tires feel when driving . Is it better to stay with the original size?

ANSWER: Janice,

First, your tire shop did you a great favor.  They gave you a viable alternative.  In this case, the tire size makes very little difference compared to the difference between tires - meaning make and model.

---------- FOLLOW-UP ----------

QUESTION: Thank you! I have one more question. The tires I got are truck/SUV tires (Michelin LTX MS). The tires that are the same size as the OME are Sedan/CUV Tires. I was told the ones I got would last longer than the Sedan/CUV tires because the Sedan/CUV tires are softer.

However it seems that these new tires are causing a rough ride which I don't like. I bought the Murano because it was more car like and road smooth.

Would the truck/SUV tires cause a rougher ride or is it just because the tires are new?
It does not feel like the same vehicle that I bought.


Tires are tailored for their application, but the difference between a crossover vehicle and an SUV is so minimal to be virtually meaningless.  So what you were told is an obfuscation to the fact that even within tires that can be used in the same application, there can be a wide range of performance.  Treadwear, traction, and fuel economy are tradeoffs and a particular make/model can be different than its competitor.  

Rough ride?  Check the inflation pressure.  Commonly new tires are over inflated and have to be adjusted down to the proper inflation pressure - which will be shown on your vehicle tire placard, which is located on the drivers door.  


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Barry Smith


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.


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.

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

You may want to visit my web site:

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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