How much air do I put in my tires? I’ve been told it’s the PSI that’s on the door jamb sticker. It says 31 PSI, but the tire says 80 PSI. Hoe does my truck know what tire it has on? BTW, '97 Ford F-150 Lariat. Thanks in advance.
Use what’s on the door.
80 PSI is what your tire will take before it explodes.
The tire pressure is the same for your vehicle regardless of the tire you use.
Double check the sticker on the door jamb. It should show the recommended tire size as well. If it is 31 psi for ‘P’ tires, it may show something higher for ‘LT’ tires. I don’t know any ‘P’ tires that hold 80 psi, but ‘LT’ tires typically do.
Also, the pressure on the sidewall of the tire is MAX PRESSURE, not recommended pressure. This tire will go on may different trucks, and will have different recommended pressures. The max pressure is the most the tires will hold safely, but will cause control problems if it is way above recommended.
If you fill a tire to its maximum pressure cold, you will exceed that pressure once you get the vehicle to highway speeds. Not only do you have a tire that gives you very bad handling, it is dangerous. If you hit a pothole, the pressure in the tire could cause it to come apart.
Like BustedKnuckles I suspect something is not right. If you’re tires take 80psi max cold then they aren’t passenger tires and the 31 psi is probably for passenger tires. Look not only at the door jamb but also in the owners manual at anything that says anything about tires. If yours take 80 cold I would probably not run them at 31.
Well, I know - and there are LT tires on the vehicle wehere the vehicle originally took P typwe tires.
To the OP: If you are using the same “Size” (meaning the dimensions indicated by the size), you need to use 15 psi more than what is on the placard!
However, if the “size” is different, you need to tell us what the 2 sizes are!
First, the PSI on the tyre is NOT a RECOMMENDED pressure. It is a MAXIUM) pressure. That is the tyre may not be able to safely support the car.
Somewhere on your car or maybe just in the owner’s manual, there should be a recommended pressure. That should be your starting point. Then there may be some adjustments for extra load weight etc.
If the recommended pressure (on the tyre) is higher than the maximum on the tyre, then that tyre is not rated to be safe for your car/tyre.
Going much over or under the recommended pressure can result in an unsafe situation. Unless you have access to a test track and do a comprehensive testing of your car and tyres it is best to stick to the recommended values.
Now after saying all that, I tend to add a few (3) psi to my tyres.
If you have changed tyre size you are in the guessing area. Someone experienced is more likely to have a better idea what might work than most others, but without the testing, you just don’t know.
If you have any questions about this and the recommended pressure for your tyres, I suggest you search on the Ford Firestone and see why today the manufacturers give you recommended pressures
Unfortunately, you’ve got a fact wrong. The vehicle tire placard has been mandated by federal law since about 1970. This greatly preceeded the infamous Ford / Firestone situation (circa 2000).
Ask your tire dealer for a load index chart for your tires, as load ratings vary by tire type and construction. The chart will specify the minimum inflation pressure per given load (mass supported by each tire). For trucks this is important; when the truck is carrying a full load, the inflation pressure required is higher than when the truck is unloaded. The inflation pressure number you see on the door jamb sticker is for the tires that the vehicle was delivered with, unloaded.
The tire pressure on the door jamb is the cold infltion pressure and the manufacturer has allowed for the tire heating up while driving. If you drain the air in the hot tire down to that pressure you are running the tire too soft and it will get hotter, handle poorly and depending on how much leeway the mfg. has built into the specs, explode. ( think Explorer and Firestone )
Be very careful trying to use the tire load tables. The pressure listed on the vehicle tire placard uses the load table as a starting point, and there’s a lot of things that take place after that before the pressure is determined.
And - NO!!! - the pressure listed on the vehicle tire placard is the pressure to be used for a fully loaded vehicle (up to the GVW). The vehicle manufacturer did extensive testing of the fully loaded vehicle at that pressure - and unless there is a supplementary sticker or a note in the owners manual, the vehicle was tested at that pressure on the empty vehicle as well.
Plus, tire sizing is standardized. It doesn’t matter who makes the tire, if you are using the same size (and the term “size” includes the letters in front of or behind the numbers), then the pressure listed on the vehicle tire placard is appropriate.
Towing? If you are towing within the limits delineated by the vehicle manufacturer, then the tire size and pressure listed on the vehicle tire placard as also appropriate.