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Matthew Wright

My Favorite Answer to the Tire Pressure Question

By January 23, 2013

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The debate over tire pressures rages on. One side argues that your tires, regardless of brand, size, age or speed rating, should be inflated to the pressure that the auto manufacturer stuck on the sticker in your door jamb. The other side argues that each tire is different, so you should ignore the vehicle's sticker and go with what is recommended by the tire itself. A recent comment from Auto Repair reader Dave sums it up tightly:
Older car's psi were set when the max. tire pressures were lower than today 44 psi. In the 1980's the typical passenger tire's max pressure was 32 psi. The load rating for the tires are about the same today as 40 years ago. My Mercedes Benz 300td has the inflation at 32 psi or the max. pressure of the tire. With today's 44 psi tire, the 32 psi would be dangerously under inflated. I have a 68 year old spare that is a 35 psi max. It also had directions for a +2 psi above max. for high speed driving.
I've never had even tire wear with the auto manufacturer's recommendations. They always had extreme out tire wear even with the original tires. I use the % load to % max psi formula plus a few extra psi for more even tire wear.
Well said, Dave! I happen to agree. Read up on buying tires and decide for yourself.
Comments
January 24, 2013 at 10:01 am
(1) JR says:

It is just like the oil change debate. The oil companies tell you to change oil at 3000 miles, the car manufacturers say 7500 miles. I usually split the difference at 5000. Funny how the stealership service departments will lean toward the 3000 when you are paying, but toward the 7500 when they pay.

With tires, the tire manufacturer may say 32psi, the vehicle mfg may say 28psi. Split the difference at 30 psi.

January 29, 2013 at 11:40 am
(2) Kevin Vieth says:

Vehicle manufacturers design their vehicles with a desired tire pressure to complement the engineered SAI (standard axis of inclination) angle to deliver optimal handling and ride comfort. The 44 psi max. pressure stamped on the side of a tire is exactly that…the maximum pressure. Tires should always be set at or close to the manufacturers recommended pressures. It is important to keep in mind that air pressure within a tire fluctuates with temperature so consider the following scenario:
You set your tire pressure to the maximum 44psi. It is a very hot sunny day in the middle of summer with the sun beating off the highway. Every 10 degrees F of temperature increase = 1 psi increase. With the added heat from your tires rolling down the hot pavement at high speed your tire pressure is now 46+ psi, much over the limit and causing center bias tread wear.

January 29, 2013 at 1:12 pm
(3) Aunt Chris says:

Matthew, as your aunt I enjoy reading your auto repair. I usually understand what you say. However this tire pressure discussion is confusing. Could you spell it out again so your old aunt can understand?

Thank you. You are a good nephew.
Aunt Chris

January 29, 2013 at 1:57 pm
(4) John Callahan says:

I love your Aunt Chris!

January 29, 2013 at 7:54 pm
(5) GEEZERguy says:

The best advice about tire pressure I ever heard was to use an old racers trick. Since racers do not use standard tires or widths they would start with the load weight that was normal, draw a chalk stripe across the tread on each tire, with the tires overinflated.
. Drive normally just far enough to rub off the chalk, then repeating with slightly lower tire pressures each time just until all the chalk is worn away. Are you familiar with this method?

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