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Tires/Tire pressure

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Question
Hi Barry,

My car's manual recommends 30 psi tire pressure. It currently has Dunlops 14" 165, which recommend 32 psi.
But everywhere I take it for maintenance, after I go back home I check the tire pressure, to find out they've been over-inflated to 40-44 psi.

I can't understand why the service technicians inflatethem so much
Is it dangerous to drive with this inflation pressure?
Can it affect or weaken the tire structure over time?
Or maybe it's a good idea to use that inflation?
I don't know... what do you think?

Thanks and best regards,

Rick

Answer
Rick,

On every vehicle sold in the US, there is a sticker commonly called the vehicle tire placard - that lists the original tire size and the proper pressure for that size.  The placard is usually located on a doorpost or in the glove box but sometimes it is located in the trunk or on the fuel filler door.

BTW, it doesn't matter who makes the tire or what pressure is listed on the tire's sidewall, if the tire size is the same as the placard, then the pressure listed on placard is also appropriate.

So if the tire size on the vehicle tire placard is the same as what you are running, then the pressure listed there is appropriate.

Assuming that the above is true, then why are people inflating the tires so high?  Under the mistaken belief that the pressure listed on the side is a recommendation - it is NOT.  It says MAXIMUM, and that is what it means.  

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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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