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Tire pressure

oe tires size 4 a ford expedition r 255/70/16 30psi front n 35 rear i got goodyear wranglers rts 265/70/16 max psi on side wall is 44psi the place were i bought them said 45psi all around does that sound right if not what sould be the correct pressure

The first thing to realize is that if you exceed the maximum pressure listed on the tire’s sidewall, you are asking for BIG problems. (Hey kids, can you say Blow-Out?)

Clearly, the folks at that tire shop are incompetent. If Capri Racer (our resident tire expert) logs in, he will be able to give you the correct inflation pressure, which is NOT 45 psi.

There is a placard/sticker with the info on Expedition. Might be on the gas tank cover inside, or on the frame near one of the doors, but it’s there. That is the pressure you should use. I suspect 30 front/35 rear is close or correct.

Would someone please translate that into English for me?

Right off the top I can tell you that the place where you bought the tyres is wrong.

That 44 psi tells you only one thing. It is not safe to put more than 44 psi in those tyres. If you need 45 psi in your vehicle then they sold you the wrong tyres!

The best source for the correct tyre pressure is what the manufacturer recommends and prints in their owner’s manual and usually on a sticker or two somewhere on the vehicle. I will guess it is 30 - 35. If so I would have to say that the 45 psi recommendation is way off.

You have chosen a different size tyre so you are now on your own (sort of).

The difference is not all that much, about 6% so I would suggest sticking with the recommendations for the original tyres. I would also avoid that tyre shop.

If it were my car, I would write a quick question to FORD and see if they will give you some guidance for that tyre size. If they supplied them in some versions of that Expedition they should have an answer for you. If you, they likely will not offer you any advice.

thanks 4 the info i think ill go with what the door says 30 front 35 rear n maybe capri racer will log on n give me some good advise

“There is a placard/sticker … That is the pressure you should use. I suspect 30 front/35 rear is close or correct.”

That would be true if he had not changed tyre sizes.

I suspect (like you jauhawkroy) that it is still right or close to right and I doubt if I would go beyond that. The OP will have to make up his own mind.

To put this inperspective:

Tire inflation pressure is all related to load carrying capacity.

A P255/70R16 has less load carrying capacity than a P265/70R16. BTW, I left the letters in there on purpose and they are important. “P” type tires are different than “LT” type tires and they have different loading characteristics - and therefore use different pressures.

But in your case, the 44 psi maximum is a clue that you have “P” type tires.

The difference between the 2 sizes mentioned means that the new tire can carry the same load as the older, but smaller, tire did using 3 psi less. So if you want to be really strict about it, you should use 27 psi front / 32 psi rear.

However, there are certain advantages to using slightly more pressure (say 3 to 5 psi more). Tires wear better, get better fuel economy, etc. The down side is they ride worse - and if you put a lot more pressure in, they bounce on rough roads and have less the grip. So if you are going to use more pressure, only use a little.