Title says it all. If the car manufacturer says 30 PSI, as Oldsmobile did for my car, and the tiremaker says 35 PSI, what am I to inflate my tires to?
The car has final say. The 35 psi rating on the tire MAY be the maximum pressure for that particular tire.
I’d go with the tiremaker.
Go with the tiremaker. The biggest problem with the Ford Explorer rollover/tireblowout flap was that the tires were UNDERINFLATED. The tires should have been inflated to between 32-35psi, and Ford insisted on 25-30, IIRC. The reason Ford wanted underinflated tires was to create a “smoother, more car-like ride.” At 35psi, you will feel more of the bumps in the road, but underinflation on a passenger vehicle is a recipe for disaster.
FWIW, on my 1/2-ton Dodge pickup (2wd) I keep the front tires at 35lbs and the rear at 30. The mfr of the tire recommends 35psi, but since I run an empty bed, 30 isn’t a problem on the rear. Now, when I add a load or a trailer, I bump it right on up to 35lbs. Note that this does NOT APPLY TO PASSENGER VEHICLES such as coupes, sedans or SUV’s. The pressure should be the same on all 4 tires for those types of vehicles.
- Dirk
I appreciate all input so far. I would love to see some cites on this, as my googling didn’t turn up anything useful.
Jonathan,
I’m going to insist here again that you pay attention to the tire manufacturer. In my previous post, I neglected to mention some information I gleaned at my local tire dealer recently:
There was a chart on the wall, displaying a “generic” tire, along with explanations of all the codes on the tire. The bottom line was, the tire is designed for the general type of vehicle it is being mounted on, be it passenger vehicle, pickup truck, mini-van or 18-wheeler; the car wasn’t designed around the tire.
- Dirk
It probably depends how your drive your car too. On the highway or in the city. I would ask the people I bought them from what is the correct amount.
The PSI on the tires is the maximum load. You should use the one the mfr recommends: http://cartalk.cars.com/Columns/Archive/1997/January/09.html
Go by the tire manufacturer’s ratings. A friend of mine went by the car manufacturer’s ratings and ended up ruining his tires.
The car manufacturer’s rating is designed to deliver a ballance of comfortable ride, handling, and fuel economy with any tire that can be safely run at the pressure indicated. Running at the tire manufacture’s rating will probably improve mileage a bit, is likely to give you a little more grip, but will make the ride stiffer. Which one to use depends on what you want from the car.
BTW, running significantly different pressures in the front and rear tires can have a noticable effect on handling.
barbitu8 is correct. The rest of the responses seem to miss a key point–tire manufacturers do not issue pressure recommendations for various vehicles.
Tire manufacturers do list maximum allowable pressure for any given tire, and it is written on the sidewall. That does not mean it’s the pressure you should use–it means it’s the pressure you should not exceed. It’s not a recommendation, but rather a limit statement. Heed it as such.
The recommended inflation pressure for a given vehicle is determined by the car manufacturer. Typically it’s on a sticker in the glove box or on a door jamb or door post (check all four doors), occasionally it’s in the owner’s manual. On most vehicles, the recommended pressure is appropriate. I would not exceed it by more than 10%.
Decades ago, it was common for manufacturers to suggest a tire pressure on the low side, trading off some tread life and cornering ability for a softer ride. This is not the norm nowadays, though the Explorer debacle indicates the practice hasn’t been totally eliminated. But if you decide not to follow the car maker’s recommendation, be aware that the tire maker is not giving a recommended pressure for use on your vehicle, only a maximum pressure for the tire.
It is YOUR car. They are YOUR tires.
YOU are the one who decides.
Can’t anybody make a decision anymore? Must we all seek authority figures to tell us what do to, and how?
Note to trial lawyers: expect full employment for the foreseeable future.
I’ll second MadScientiestMatt - keep all tires with equal pressure!
Oh, I see DirkGntly also said that. I might as well try and throw some useful info: Every month or so, when you check your tire pressure with a good store-bought gauge (you’re not relying on gas station pump gauges right?!) - check for even tread wear too (primarily on front-front and back-back). Also, when it snows, you might want to drive on virgin snow and see if your car tracks straight (back wheels rolling over front wheel tracks).
The Goodyear Tire & Rubber Company says this (from http://www.goodyear.com/gov/policetires/inflation.html):
“Goodyear recommends that tires be inflated to the vehicle manufacturer’s recommendation as found on the Vehicle Tire Information Door Placard or the Vehicle Owner’s Manual…Goodyear retailers should only recommend the vehicle manufacturer’s correct air pressure as outlined on the Vehicle Tire Information Door Placard. In many cases, negative factors such as poor ride or irregular wear could occur if maximum air pressure is recommended to customers.”
This site (http://www.geocities.com/waynem48/mechanic/tirepressure.html) says:
“The amount of air required to properly inflate a tire depends on the size and type of tire, the vehicle application (size and weight), vehicle loading (normal or extra loading), and driving conditions…Increasing a tire’s inflation pressure beyond the recommended amount will reduce rolling resistance, thereby
improving fuel economy. But the trade-off is a harsher ride and increased risk of tire damage when encountering bumps…So how much air is the “right” amount to use? The simple answer is because every application is unique, it’s best to always refer to the recommended inflation pressures specified by the vehicle manufacturer. These are generally listed in the owner’s manual or on a decal in the glove box or door jamb.” [Emphasis mine]
Michelin (http://www.michelin.ca/ca/eng/local/guide/lesson4.html) says this:
“The correct pressure varies from vehicle to vehicle and depends in part upon driver preference. Each vehicle has a recommended inflation pressure, usually found on a placard on the door section, door post, glove door, or fuel door.”
Please note above that the correct pressure is vehicle-specific, not tire-specific.
This site (http://www.startribune.com/stories/435/908952.html) addresses this very question and says:
“The correct answer, as confirmed by the tire companies, is to set your tires to the pressures recommended by the automaker.” [Emphasis mine]
So what tire manufacturers recommend is to use the pressures recommended by the vehicle maker. They do not recommend routinely using the maximum inflation pressure.
One more thought–the car makers expect you to use tires of a certain specification, also listed in the owner’s manual &/or on a sticker. Using a fundamentally different type of tire can make everything else meaningless.
By the way, I found a few sites where someone recommended using the maximum pressure listed on the sidewall. I don’t find them nearly as credible as the engineers from tire manufacturers and vehicle manufacturers. Frankly, I think they’re talking out their nether orifices.
Enter the following words in the Google window: tire recommended inflation pressure maximum
“Humm, how much oil does my car take? I wonder if I would be better off following the manufacturer recommended quantity, or just coming up with one on my own.”
^^ Joe Consumer ^^
Isn’t this the reason The Straight Dope is here? Clearly there is a good reason that a given tire on a given vehicle might rate a differing “best” inflation? Perhaps it is on the onus of car/truck drivers to know all of this. A commercial pilot is mandated to know the specifications of his/her aircraft. To do a walk-around - hey a new GE engine - how many hours on that? What about the Rolls-Royce engine it’s paired with? Brand new Good Year Tires! Let’s double check the tire-pressure - it’s much colder at LaGuardia than LA!
Gary T has been providing damn good infos. Carry on.
Dear Joe Idiot:
Thank you for your inquiry.
Due to repeated questions such as yours, we have added (since, say 1915) a feature to our engines known as an “oil dipstick” - it has markings indicating the level at which there is not enough oil in the crankcase, as well as when there is too much oil in the crankcase.
Hoping you eventually learn how to use your dipstick, we remain:
Faithfully yours,
Customer Service for total incompetants
That would be funny if it weren’t true! For instance, the dipstick on my Ford 2001 Mustang Cobra is like a bicycle-brake cable and the ‘dip’ part of it shows a min-max - but no indication of what is right. How did I find out? I asked on the BON message board. And after my first oil change (Ford suggests 9000 miles - I’ve just turned 9000 and have done two - another coming up soon).
My tires are (from memory) Goodrich 295/45 ZR 17 and feature warnings (not verbatim) about overloading or over-inflating. The ZR rating means something about the tire being rated for speeds upwards of 160 MPH. 137 MPH doesn’t come close, so I’ll have to take their word.
It’s a good thing every car owner reads their manual and knows this stuff, right?