I just bought a used car. Tire says 44 psi, door says 30 psi.?

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You are getting poor advice from some, decent advice from others.
The PSI on the tire is the maximum safe inflation for the tire, and they have no idea what car you are putting it on. My old tires had a max of 44 lbs, my new tires have a max of 51, because tires have gotten better. BUT MY CAR DIDN'T GET HEAVIER!
Unless you have mad a drastic change in custom wheels and tires, the best advice is to go by the door placard for comfort, then add a little to improve handling and mileage. If the door says 30, you will be happy with 35 or so. If you go the limit on the tire, the centre will wear out first, bad weather handling will not be good, and the ride will be harsher.
If you have custom wheels and tires that are a lot different from the original sizing, pressure requirements could be a little different from the door placard, so you should contact a distributor for the tires to get a specific recommendation based on the load your car actually puts on the tire....Show more

Tires have gotten better over time, if you remember most tires used to say 35 PSI max. (talking standard passenger car) and door would say 30 PSI. Most people would run about 32 PSI. Now tires say 44 PSI max. So you dont want to run 30 PSI in that tire, thats 14 PSI under max. Split that14 PSI in half and start there 37 PSI, then go up or down depending on preference. The closer to the 37 PSI you can stay the better wear you will get on the tire.

J. Adam Physics proffesor...Show more

first, 44 psi is pretty high for a commercial car tire, sounds more like a truck tire. when you put less air in a tire you will have a softer ride, but it is a little harder on the sidewall because it flexes more, and you loose a little fuel economy because a nice round hard tire rolls easier than a soft one. the rating on a tire is a maximum pressure, the idea is for the tread to be flat on the surface, to get maximum traction and tread life, too much pressure and the center will baloon out and cause uneven, heavy center wear, too little pressure and the center will push in causing uneven heavy outer wear. this being said, you can see what the affect of weight has on how the tire sits, more weight, the tire will squish causing heavy outer tread wear. this is why this tire may be best at 44 psi on a heavy pickup, but on a light car 30 might give you the same "footprint". i would never go over the tire recommendations, but start with the car's suggestion, look at the tread from time to time, if the grooves are showing heavier center wear, take a couple pounds out, if it looks like heavy outer wear, add a few. the car company is giving specs for the tire they put on the car, it may not be exactly right for the tire you buy later, same thing goes for the tire company, they don't know the wieght of your car, it is a generalization....Show more

You should read a bit more carfully.

The door probably says something like "recommended cold inflation pressure 30 psi"

The tire says "44 psi max pressure"

Which one is the recommendation and which one is the safety warning to protect the tire manufacturer from liability lawsuits?

Or put another way, since the tire manufacturer has absolutely no way of knowing what sort of car the tire is going to be mounted on, wouldn't you go with what the folks who built the car say? The recommendation on the door jamb applies to any tire of any brand or model so long as it is the same size and load index as the tires originally fitted to the vehicle. It is a myth that tires of different brands have different inflation requirements.

If you go to the tire manufacturers web site they will also tell you to follow the recommendation on the door jamb....Show more

44 Psi To Bar...Show more