Fill Tire Pressure To What Tire or Vehicle Says?

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A friend asked me if they should fill their tires with what the tire has on it or what the car has listed on the drivers door pillar?

I told her to put in what the tire says not whats on the door because she has newer tires that say max press 45 and the car says max pressure 35psi. I also said she should not put the max pressure in them if they are cold because they expand with heat as they get hot while driving.
The gas station says always go with what the car says and refused to fill them up to what the tire says.

this is confusing to some car owners what is your opinion?
 
The door jamb ks for best ride. It depends on the tire, load and your preferences.

The lifeliner gls tires on my focus go to 44, ford recommends 32. I run 38 in the front and 34 in the rear. Depends on many things.
 
Yes to the above.

The door jamb lists the correct pressure. The tire lists the maximum allowable pressure.
 
Go with the door jam.

At least down here, they usually give two pressures, one "normal", and one "loaded", which is usually 4psi more.

I always run the higher pressure, as you never know when you are going to end up[ "loaded", and I prefer how they drive that way unloaded.
 
This is for an early 90's car tires have changed since then on our old truck the door frame says 32 the tires called for 48-50 i used to put 45
 
Originally Posted By: crazyoildude
The gas station says always go with what the car says and refused to fill them up to what the tire says.

The gas station is right.

Use the pressure that's on the vehicle placard, and set it when the tires are cold.
 
Originally Posted By: Miller88
The door jamb ks for best ride. It depends on the tire, load and your preferences.

The lifeliner gls tires on my focus go to 44, ford recommends 32. I run 38 in the front and 34 in the rear. Depends on many things.


Agreed; the manufacturer (for most vehicles) is concerned with a nice ride without compromising handling too much.

Anyone else here seen an early 00s Jeep Grand Cherokee with the inside and outside of the fronts worn to nothing? When I got my 04 GC with 18k on the clock, the door jamb said 30 IIRC and the front tires had been replaced just before I bought it.

After a few thousand miles I noticed the uneven wear and increased pressure to 35 (max for that tire). Once I got new tires, I kept my Michelins at 42 and they wore nice an even, going over 70k before I sold it and still had another bunch of miles to go.

So OP short answer: start with what is on the door jamb. If you want factory ride and don't care about tire wear, leave it. If you want tires to wear evenly, adjust as necessary.
 
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Originally Posted By: Kuato
So OP short answer: start with what is on the door jamb. If you want factory ride and don't care about tire wear, leave it. If you want tires to wear evenly, adjust as necessary.

Not sure I follow your logic. In my experience, the wear is the most even at factory recommended PSI. If I increase PSI above that in my 530i, I get uneven wear.
 
Originally Posted By: crazyoildude
This is for an early 90's car tires have changed since then on our old truck the door frame says 32 the tires called for 48-50 i used to put 45


Everyone in this thread has correctly told you to go with what the door says. Yet here you are trying to justify putting the pressure to what the tire says. If you don't want people's thoughts, which are all right by the way, then don't ask.
 
Originally Posted By: crazyoildude
the tires called for 48-50

The tires don't call for anything. The number on the tire is just a max allowable PSI that the tire can sustain. It has nothing to do with what you should be running. The same tire could be used by hundreds of different vehicle makes and models. The tire manufacturer has no idea what vehicle you're going to mount the tire on, hence they are not in a position to tell you what PSI you should be running. Only the vehicle manufacturer can recommend the correct tire pressure.
 
Saw an old Explorer today with no tire squat whatsoever,these were the Firestone/Explorer rollover generation SUVs,and Ford recommended 27(??)psi for them or else the handling gets all squirelly.This driver was being ultra cautious taking corners.Tires must have had 38psi in them all.
 
My placard recommends 32 psi. Tires, max 51. I set the tires at about 40-42 psi. At about 24k miles the tires look fantastic. Tires rated at 45k. I get the tires rotated every 5k.
 
On a side note, I bought new General tires for the Subaru yesterday. The handling was odd, so I checked when I got home. 30/30/35/45. The placard says 29/30. I fixed that and it's much better.

Why is it so hard to find a shop that will do things properly the first time?
 
Originally Posted By: Bandito440
On a side note, I bought new General tires for the Subaru yesterday. The handling was odd, so I checked when I got home. 30/30/35/45. The placard says 29/30. I fixed that and it's much better.

Why is it so hard to find a shop that will do things properly the first time?


Because guidance councilors don't tell the brainy kids to get into the tire biz.
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And I've done it for a bit.
 
If you check the owners' manual, some cars will also instruct to bump up the pressure up for high speed driving; so a bump up in PSI is not always just for load reasons.

The measurement of the tire's pressure is always done when "cold" which means the tire hasn't been driven for awhile. "cold" doesn't mean a specific temperature, it means whatever is the ambient temperature in which you are driving the car.

The stuff about it exceeding max pressure when it's hot due to load is already been accounted for in the max pressure statement.
That being said, if you're running at max pressure, and your load is such that you're tires are heating up to the degree that their temp and pressure increasing well past max; you are likely abusing your tires and not using them in their designed specification.

So your advice was bad, the gas station's advice was good.

anyway, it's not confusing to anybody who spent any time working reading up on tires or the owner's manual. If you want more details, read articles on tirerack which may explain it step-by-step.
 
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i totally disagree the tire business done correctly is very very profitable, the mark up is insane on a product that every vehicle and almost anything else that rolls needs.
 
I always run my tires about 2 psi higher than the recommended door sticker. Most manufacturer numbers are based on a combination of riding comfort, performance and fuel economy considerations. I tend to favour the performance and fuel economy aspects and I may give up a bit of comfort. If I am wrong about that, I have lost nothing and there is no harm to come from it.

I always remember the old Ford "Exploder" tire ratings were based too much on comfort (too low) and not enough on performance , though I understand that the whole situation was a bit more complicated than that.
 
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